A cam is a mechanical element, usually a hardened profiled disc or block, that rotates and, through the action of a cam follower/ roller and linkage, imparts a precise reciprocating motion to a valve, pump or other component. In large two-stroke marine engines, cams are driven from the camshaft, which in turn is driven from the crankshaft at the same speed (two-stroke) or half speed (four-stroke).

Types of cam profiles used:

1. Tangent (tangential) cam - Flanks are straight lines tangential to the base circle and rise/ fall arcs. Simple to design and machine, gives moderate acceleration, used for fuel pump and exhaust valve drives where a dwell is not essential.
2. Convex / circular arc cam - Flank is an arc of large radius. Gives a smoother acceleration change (no shock at points of inflection), used for exhaust valve cams to reduce noise and wear at high speed.
3. Concave cam - Rarely used; short dwells, higher contact stresses.
4. Zero-lift / parallel and dwell cams - Have base circle only; used for indicator drives where a steady datum is required.
5. Negative cam (see part b) - Used on exhaust valve air spring/hydraulic systems of large two-stroke engines.

Functions and how cam profile affects operation:

• Exhaust valve cam: Opens the exhaust valve against the returning force (air spring or hydraulic). Profile shape controls valve lift, opening/closing timing, periods of dwell when valve stays fully open, and rates of acceleration/deceleration. Long dwell and gentle flanks reduce valve seat impact and stress.
• Fuel pump cam: Rises to displace the plunger for injection. The number of cam lobes and profile determine injection timing, rate of injection (injection pressure build-up), and whether the pump is single- or multi-ram type. The rise must give the required plunger velocity to build fuel pressure quickly.
• Starting air distributor cam: A distribution disc/cam with a series of lobes around its circumference that opens the pilot valves of the air-start valves in correct sequence with cylinder firing order. The number of lobes equals the number of cylinders; profile size sets the duration of air admitting window.

A negative cam is a profile that provides a large movement (lift/dwell) over most of its revolution and only a short period at low (base circle) lift. In practice it is often a cam in which the "active" portion is a depression or a reduced-radius segment.

Purpose: In MAN B&W (and similar) large two-stroke engines with hydraulically operated exhaust valves, the exhaust valve is opened by hydraulic oil pressure from a high-pressure pump driven by the cam; the valve is closed by the valve air spring. A "negative" or long-dwell cam supplies hydraulic oil pressure through most of the rotation so that the valve is held closed under hydraulic pressure, and only at the point where closing is required does the cam lift fall, releasing pressure so the valve air spring slams the valve shut. In this scheme the valve is opened by a fall in the cam lift rather than a rise, hence "negative" cam.

Constructional features: The cam has a large base circle for the majority of the revolution (hydraulic valve held closed) and a single machined depression or reduced-lift sector of short angular extent corresponding to the exhaust open period. It is precision-ground, case-hardened steel, mounted on the camshaft, and the profile is machined to give a fast pressure release for rapid valve closing but with controlled cushioning to avoid hammering.

Typical use: This negative/short-dwell cam principle is used on the exhaust valve hydraulic drive of slow-speed two-stroke engines (e.g. MAN B&W MC/MC-C series using the "fuel oil valve actuator" and hydraulic exhaust drive), where it provides shock-free, precisely timed exhaust valve operation without a conventional high-speed spring cam mechanism. It reduces noise and wear compared to positive cam systems.

Asbestos is a naturally occurring mineral that was widely used in ships because of its excellent heat resistance, electrical insulation properties, and strength. However, due to its significant health risks, the International Convention for the Safety of Life at Sea (SOLAS) now prohibits the installation of any new materials containing asbestos on ships. This regulation, outlined in Chapter II-1, Regulation 3-5, and clarified by MSC.1/Circ. 1379, has been in effect since January 1, 2011.

Historically, asbestos was used in various ship components, including:

• Thermal insulation: Asbestos was commonly used for lagging on boilers, steam pipes, and other hot surfaces.
• Gaskets and glands: It was a key component in gaskets, valve glands, and associated pipework to ensure tight seals.
• Fire protection: Its fire-retardant properties made it a popular material for cladding on bulkheads and other fire-resistant structures.
• Friction materials: Asbestos was found in machinery components like brake linings.

The primary health risk from asbestos comes from inhaling airborne fibers. These fibers are microscopic and can be present in the air even when it appears dust-free. When inhaled, these sharp, needle-like fibers can penetrate and become lodged in the lungs, leading to several serious and often fatal diseases. These include asbestosis (a chronic lung disease causing scarring), lung cancer, and mesothelioma (a rare and aggressive cancer of the lining of the lungs, heart, or abdomen).

While less dangerous than inhalation, direct contact with asbestos fibers can also cause wart-like lumps to form on the skin. While these are not considered life-threatening, they highlight the need for careful handling.

• All asbestos-containing items, such as gaskets and seals, should be thoroughly wetted before handling. Such items can usually be replaced without special precautions if properly soaked and must be carefully disposed of afterward.
• When working with materials containing asbestos:
  • Dust generation should be minimized through careful handling.
  • Hand tools are preferred over power tools.
  • The item to be worked on should be thoroughly pre-wetted.
• Efforts should be made to control dust and movement by:
  • Enclosing the affected area
  • Using portable dust extraction equipment
  • Ensuring that vented air is released away from areas where personnel might inhale it
• Access to work areas should be restricted to only essential personnel.
• If practical, the working area should be enclosed, and appropriate warning signs must be displayed.
• Individuals not equipped with proper protective clothing and respiratory equipment must be excluded from the area.
• Large plastic sheets should be used to collect all waste materials generated during the work. At the end of the task, these sheets should be folded and placed in airtight containers for safe disposal.

PROCEDURE FOR REPLACING A MAIN ENGINE CYLINDER LINER

General preparation

• Obtain the engine maker's overhaul manual and the vessel's planned maintenance and risk assessment for the job.
• Inform the chief engineer, obtain permission, log the job, and prepare a permit-to-work / risk assessment covering hot and moving machinery.
• Stop the engine, close the engine room ventilation to that space as required, and drain and isolate the cooling water and lubricating oil to that unit.
• Bar the engine to bring the piston of the unit to about TDC or a position where the connecting rod is accessible and the piston rod can be disconnected from the crosshead.

Dismantling sequence (removal of old liner)

1. Shut and blank off the cylinder jacket water supply and return valves of the affected unit; drain the jacket cooling water.
2. Remove the cylinder cover (cylinder head) complete, together with its exhaust valve, injectors and starting valve, and land it on a suitable crib.
3. Remove the piston: secure the piston rod from turning, slacken and remove the crosshead/piston rod clamp or shrink-fit coupling, then lift the piston (with rod) out of the liner using the ceramic piston lifting rig or appropriate tackle, and land it on blocks clear of the work area. Protect the piston crown and ring grooves.
4. Remove the scavenge/ piston underside parts as required and relieve the liner lands.
5. Remove the stuffing box (piston rod gland) from the liner bottom to clear the bore seating.
6. Mark the liner and the liner land for correct replacement orientation and for the port alignments.
7. Disconnect the liner cooling water connections and any liner lifting/pulling gear arranged.
8. Using the lightweight jacking screws or the purpose-made liner lubricant/ lifting arrangement provided, break the liner from its seating; support the liner on a sling and lift it cleanly out of the jacket, watching the scavenge ports and the symmetrical handles.

After removal, examine the liner water side and jacket bore for scale, corrosion and fretting.

Parts requiring close attention during the lift

• The piston rod clamp joint and the sealing faces.
• The liner seating faces and the jacket top face - any dirt or burr will distort the new liner.
• The scavenge ports, liner lands and flame ring (if fitted) at the bore.
• The condition of the port area and the seating at the bottom of the liner.
• The O-ring or soft packing seals between liner and jacket water side - replace with new ones of the correct material.
• The crown of the liner bore (top) where the compression ring and worn ring grooves have the highest temperature.

Fitting the new liner

• Clean the jacket bore thoroughly, inspect for cracks and verify the fit-up dimensions and that the water spaces are clear.
• Fit new rubber O-ring seals (or annealed soft packing) in the grooves, thoroughly greased.
• Lower the new liner using a suitable sling arrangement, entering the jacket gently.
• Set the liner lands to align the scavenge ports with the jacket ports, checking the axial and circumferential location marks.
• Check the liner sits in full contact on its seating by feeler/gap; the liner and jacket must mate without rocking.
• Jack up and re-check.
• Reconnect the piston rod clamp, refit the stuffing box, re-land and secure the piston in the liner with new ring condition checked, and refit the piston crown.
• Refit the cylinder cover and torque the studs in the correct sequence to specified values.
• Reconnect the water and oil connections, ensure the ports and sealing are correct.

Important checks before and after fitting

Before: liner bore and surface finish, correct liner identification/oversize, ring/groove dimensions, port alignment, cleanliness of jacket, condition of new sealing rings, torque specifications.

After: scram the piston in TDC/B DC, check piston/liner clearance and ring gaps, verify scavenge port alignment, pressure test the cooling water side, bar engine round to check no tight points, and finally leak-test and run the unit up.

Pressure testing the cooling water side of a cylinder cover

• With the cover removed from the engine and cleaned, blank or cap all water passages including the injector and valve cores as required.
• Fill the cooling water space with water and apply hydraulic pressure using a manual or powered test pump.
• Use the maker-specified test pressure (typically 1.5 times working pressure but as per class standing instructions).
• Hold the pressure for a specified time (usually 15 to 30 minutes) and examine all welded seams, machined surfaces, the nozzle deck and the valve seats for weepage or leakage.
• Any leak is a condemnation; the cover must be repaired or replaced.
• On successful test, drain, dry and apply a protective coating (or re-fit with new seals), then refit to the engine.

Crosshead Guides in Large Reciprocating Engines

Reason for Fitting Crosshead Guides

Crosshead guides are fitted to large, slow-speed reciprocating engines to absorb the side thrust created by the angular movement of the connecting rod during the power cycle. This side thrust, if left unmanaged, would force the piston hard against the cylinder liner, leading to excessive wear on both the piston and the liner. The guides ensure the piston rod maintains a perfectly vertical, linear path 📏.

Why 'Ahead' and 'Astern' Faces are Required in Uni-directional Engines

Even in engines designed to run only in one direction (uni-directional), both "ahead" and "astern" guide faces are required to manage the alternating side thrust that occurs during the engine's internal cycle:

• Ahead Thrust (Power Stroke): As the piston moves downward under power, the connecting rod's angle pushes the crosshead guide shoes against the "ahead" guide face.
• Astern Thrust (Compression Stroke): When the piston moves upward to compress the air, the connecting rod's angle reverses, pushing the crosshead guide shoes against the "astern" guide face.
• Balanced Wear: Having two active faces helps distribute the load and ensures more even wear across both the guide shoes and the guide surfaces, thus extending their service life.
• Maneuvering & Startup: The forces on the crosshead guides can temporarily change direction, even in a uni-directional engine, during startup, shutdown, and maneuvering (e.g., when running on low air pressure or during a misfire).

The crosshead guide clearance (the athwartships gap between the guide shoe and the guide face) is a critical measurement checked and adjusted using feeler gauges and shims.

Checking the Clearance

1. Position the Engine: Engage the engine's turning gear and position the crank to push the crosshead and its guide shoe hard against one side (either ahead or astern) of the crosshead guide. This maximizes the gap on the opposite side.
2. Measure the Gap: Use a feeler gauge to accurately measure the gap between the opposite guide shoe and its guide face. This measurement represents the total athwartships clearance (often called the 'running clearance').
3. Manufacturer's Data: Compare the measured clearance with the maximum allowable clearance specified in the engine manufacturer's manual.

Adjusting the Clearance

1. Loosen and Access: Loosen the securing bolts for the guide bars to gain access to the shims, which are thin metal plates positioned between the guide bars and the engine's mounting points.
2. Add or Remove Shims:
   • To decrease the clearance (tighten the guide), a suitable thickness of shims is removed.
   • To increase the clearance (loosen the guide), shims are added.
3. Re-check: The guide bars are then bolted up to the specified torque, and the clearance is re-checked to ensure it is within the acceptable range specified by the manufacturer.

Limiting the crosshead guide clearance to the manufacturer's specification is essential to maintain the mechanical integrity and long-term reliability of the engine:

1. Maintain Piston Alignment: Limiting clearance ensures the piston rod stays centered within the cylinder bore, which is vital to prevent excessive and uneven wear on the cylinder liner and piston rings.
2. Prevent Impact Damage (Knock): Excessive clearance allows the crosshead shoe to impact the guide face when the thrust reverses. This repeated, heavy 'knocking' causes damage and fatigue to the guide shoes, guides, and connecting rod assembly.
3. Reduce Dynamic Stresses: Uncontrolled clearance increases dynamic stresses, which can lead to fatigue failure and cracking of the white metal bearing material on the guide shoes.
4. Ensure Proper Lubrication: The correct clearance is necessary to maintain the hydrodynamic oil film between the sliding surfaces. Too much clearance can disrupt this film, leading to metal-to-metal contact.
5. Minimize Noise and Vibration: Tightening the clearance reduces the impact between components, thereby minimizing engine noise and vibration.
6. Prevent Oil Contamination: Correct alignment helps the piston rod pass cleanly through the stuffing box seals, which is crucial for preventing combustion products from contaminating the crankcase lubricating oil.

Handling Slack Holding-Down Bolts and Fretting in a Main Engine

Slack holding-down bolts (HDBs) indicate a serious issue affecting the structural integrity of the main engine seating. These bolts are responsible for securing the engine bedplate firmly to the tank top. If they become loose, the rigid connection is compromised. The presence of fretting—seen as fine reddish-brown or black metallic powder—confirms that relative movement has occurred between contact surfaces. This condition can lead to bedplate misalignment, crankshaft distortion, and eventually structural damage if not addressed promptly.

As a newly joined engineer, the situation should be handled systematically as follows:

1. Immediate Assessment and Reporting

• Identification and Mapping: Identify all slack bolts and assess the extent of fretting. Use feeler gauges to check for gaps between the bedplate, chocks, and tank top, which would indicate loss of proper contact.
• Crankshaft Deflection Measurement: Take a complete set of crankshaft deflection readings. Any distortion in the bedplate due to loose bolts will reflect as abnormal deflection values.
• Reporting: Report the findings immediately to the Chief Engineer. Since this is a pre-existing or “latent defect,” it should be recorded in the engine logbook to document the condition at the time of joining.

2. Investigation of Fretting

• Chock Condition: Inspect the chocks (metallic or epoxy resin type) for signs of wear, cracking, or deformation. Fretting usually indicates that these supports have deteriorated due to continuous vibration and movement.
• Side and End Chocks: Examine side chocks and collision (end-stop) chocks. When main holding-down bolts are loose, these components often absorb additional forces and may also be damaged.

3. Short-Term / Immediate Rectification

If immediate corrective action is required (e.g., during port stay):

• Cleaning: Clean the affected area thoroughly to remove fretting particles, oil, and debris. This helps in proper inspection and monitoring of further movement.
• Re-tightening of Bolts: Tighten the slack bolts using the manufacturer’s specified method, typically with hydraulic jacks, to the correct tension.
• Caution During Tightening: If chocks are worn or uneven, tightening alone may pull the bedplate down unevenly, worsening alignment. Therefore, tightening should be carried out carefully while monitoring crankshaft deflections.
• Locking Arrangements: Ensure that locking devices such as lock nuts or securing arrangements are properly fitted to prevent recurrence of loosening.

4. Permanent Corrective Action

If fretting damage is significant, temporary tightening is not sufficient, and long-term repairs must be planned:

• Re-chocking: The engine may need to be partially lifted, old chocks removed, and the seating surfaces machined or ground to restore proper alignment.
• Epoxy Resin Chocking: Modern practice involves the use of pourable epoxy resin (e.g., Chockfast), which provides uniform contact between the bedplate and tank top, eliminating localized stress points and reducing the risk of future fretting.
• Inspection of Fitted Bolts: Check the condition of fitted (reamer) bolts, which ensure precise alignment. These must not be damaged or sheared.

5. Follow-up and Monitoring

• Regular Tightness Checks: After re-tightening, recheck bolt tension after initial running (e.g., after 24 hours) and continue periodic checks to ensure stability.
• Lubricating Oil Analysis: Monitor lube oil for increased metal content (such as iron or tin), which may indicate abnormal wear due to misalignment.
• Vibration Monitoring: If possible, conduct vibration analysis to detect any abnormal changes in engine behavior or structural resonance caused by the earlier loosening.

• Over time, the high-tensile steel tie rod can experience creep, a time-dependent deformation under sustained load. This gradual elongation reduces the initial tension.
• Repeated cycles of gas pressure and engine vibration can induce fatigue in the tie rod material. Microscopic cracks can develop, leading to a reduction in effective length and consequently, preload loss.
• Incorrect tightening during installation or maintenance can result in insufficient initial tension. This is often the root cause of premature slackness.
• Settlement or movement of the engine foundation can induce stresses that relieve the tension in the tie rods. This is especially true if the foundation is not properly designed or maintained.
• Corrosion at the threads or under the nut can weaken the connection, effectively inducing slackness.
• Hidden damage (e.g. cracking) to the tie rod itself can lead to apparent slackness as the rod's effective length is altered.

• Thoroughly clean the tie rod threads, nuts, and landing areas to remove dirt or fretting dust.
• Ensure the pinching screws and main bearing jack bolts (if fitted) are slackened before retightening.
• Apply the correct lubricant as recommended by the manufacturer to ensure smooth tightening without additional stress points.
• Use the hydraulic pump and jacks to apply tension to the tie rods according to the manufacturer's specified stages, sequence, and hydraulic pressures.
• Measure the elongation of the tie rod after tightening and compare it with the manufacturer’s recommended values.
• Tighten the pinching screws and main bearing jack bolts after completing the tie rod tightening.

Minimizing Future Slackness:

• Regularly monitor tie rod tension and inspect for signs of fretting, slackness, or brown dust.
• Follow the manufacturer’s tightening procedure and PMS schedule for maintenance.
• Maintain engine operation within the specified load, temperature, and speed limits to prevent excessive stress or vibrations.
• Conduct routine inspections of running gear alignment, foundation bolts, and vibration dampers to ensure proper operation and minimise structural movement.

Tightening sequence:

• Slack tie rods result in uneven loading of the engine on the transverse girder, leading to crankshaft misalignment. This misalignment can damage bearings and cause uneven wear on other engine components.
• The relative movement between the engine structure caused by slack tie rods leads to fretting, a type of surface wear that occurs due to microscopic vibrations.
• Fretting can cause accelerated wear on the crosshead guide, cylinder liner, and stuffing box due to misalignment.
• The overall alignment of the engine and running gear can be compromised, impacting performance and potentially leading to damage.
• Excessive vibration of the engine may lead to failure of the components, which may be even extended to failure of turbocharger bearings
• The vibrations can further loosen foundation bolts and chocks, exacerbating the problem.
• In severe cases, slack tie rods can lead to damage of the bedplate, frame, and entablature, requiring costly repairs.

Things to follow before carrying out maintenance,

• Inform the bridge before going inside the CO2 room.
• Start ventilation blowers first and the room should be ventilated for some time.
• Go with a person with proper communication equipment.

Weekly

• Check all cylinders are properly secured.
• Make sure that nothing has been placed to interfere with the normal operation of the system
• Check all the operating levers and their accessories are properly tight.
• Check clamping.
• Check valve actuator.

Once every month

• All the weekly checks
• Inspect for piping and equipment for mechanical breakage
• Operate the valve several times and make sure that it does not stick
• Open the cabinet door and check the alarm and ventilation cut off working.

Once In Every Year

• All the monthly checks
• Cylinder should be weighed to determine the CO2 content
• If the net weight is decreased by 10% of the actual weight, the cylinder should be recharged

Once In Every Two Years

• All the checks in yearly
• Blow through all piping with service air @ 25 bar pressure or Co2 to make sure that the line is not blocked

Once In Every Five Year

• All the above
• Spring loaded relief valve pressure test @ 180 bar.

10 Yearly

• Cylinder pressure test @ 250 bar (after the first 10 years, the cylinder is to be pressure tested every 5 years)

15 yearly

• Pressure testing of the line by a suitable liquid
• Cylinder to master valve: @ 170 bar
• Master valve to E/R or Cargo hold valve: @ 80 bar
• E/R or Cargo hold to nozzle: @ 6-7 bar

Machinery condition monitoring is the systematic and regular measurement of parameters of a machine (vibration, temperature, pressure, wear debris, oil condition, etc.) that reflect the actual physical condition of the machine, while it is operating or during routine down periods, in order to detect the onset and development of deterioration or faults. The measured values are recorded and compared against baseline/reference values and trended over time so that the rate of change and the approach of the machine to a failure limit can be assessed. Its purpose is to plan maintenance on the basis of actual condition (condition-based maintenance) rather than on a fixed calendar or running-hours schedule, so that a component is serviced just before failure occurs, avoiding both unnecessary overhaul and unexpected breakdown. It allows early warning of developing faults, extends machinery life, reduces downtime and maintenance cost, and improves safety.

1. Vibration monitoring: Using portable or permanently installed vibration analysers/ accelerometers. Measurements of overall vibration level and of the vibration spectrum (frequency analysis) are taken at designated measuring points (bearing housings of the engine, turbocharger, pumps, purifiers, generators). Readings are compared with the baseline and with the ISO/classified machinery vibration standards, and trended.
2. Temperature monitoring: Jacket cooling water, exhaust gas, scavenge air, bearing metal and oil temperatures, measured with thermometers, thermocouples or resistance temperature detectors, and compared against alarm/limit settings.
3. Pressure monitoring: Cylinder compression and firing pressures, scavenge air pressure, lubricating oil and cooling water pressures, recorded and trended against load.
4. Oil analysis / tribology: Regular sampling of lubricating oil (engine, purifier, gearbox, stern tube) sent to a shore laboratory or tested on board for wear-metal content (spectrometric analysis), TBN, viscosity, acidity, water, insolubles. Rising wear-metal concentration indicates bearing/piston/liner wear.
5. Wear measurement: Internal micrometer measurements of cylinder liner bores, piston ring/groove clearances, crankshaft deflection readings, bearing clearances (bridge gauge readings), taken at survey intervals and recorded against running hours.
6. Performance/indicator analysis: Draw and analyse indicator diagrams (p-compression, p-max, power) and out-of-phase diagrams; calculate specific fuel consumption to detect combustion deterioration.
7. Visual and ultrasound inspection: Borescope inspection of combustion spaces, listening, and ultrasonic thickness measurement of pipes and shells.

The key is trend analysis. A single reading is of limited use; it is the change with time that indicates condition. By plotting a measured parameter (e.g. bearing temperature or vibration velocity mm/s) against running hours or calendar time, a baseline operating band is established. A slow, steady rise within the band shows gradual, normal deterioration; an accelerating rise forecasts an approaching failure; an abrupt step change indicates a sudden fault. The gradient (rate of change) of the curve is used to predict the remaining useful life until it reaches the alarm or trip limit. By comparing trends across engines and across measuring points, engineers can identify which component is degrading, can schedule the overhaul before failure at the most convenient time (e.g. in port), can optimise spare-part usage, and can evaluate whether an earlier repair was effective (the trend should return to the baseline). Thus monitoring converts routine maintenance into predictive, condition-based maintenance, giving early warning and allowing the machinery to be operated safely until a planned intervention.

(i) Radiographic Testing

A non-destructive testing method that uses penetrating radiation (X-rays or gamma rays) to detect internal flaws in materials. The radiation passes through the material, and variations in its intensity are recorded on a X-ray film. Darker areas on the image correspond to denser regions (defects) within the material. X-ray radiography is better suited for smaller defects, while gamma radiography can penetrate thicker materials and detect larger flaws.

Advantages:

• Highly sensitive to internal discontinuities
• Relatively less time-consuming
• Produces permanent records.

Disadvantages:

• Involves radiation hazards, requiring specialized training and safety precautions
• Necessitates skilled operators
• High initial equipment cost.

(ii) Ultrasonic Testing

Employs high-frequency sound waves (ultrasonic) to detect internal and sometimes surface flaws. The ultrasonic waves are transmitted into the material, and any reflections caused by discontinuities are detected and measured. Methods include pulse-echo (single transducer sends and receives waves) and through-transmission (separate transducers transmit and receive).

Pulse-echo method:

Transmission method:

Advantages:

• Effective at detecting deep-seated flaws
• Determines flaw depth, size, and location
• Portable and relatively easy-to-use equipment
• Good accuracy and reliability.

Disadvantages:

• Sub-surface discontinuities near the surface may be difficult to detect
• Challenging to examine irregularly shaped or rough components
• Requires skilled interpretation of the results.

(i) Metal locking is a cold-working repair method for fractured castings. The process involves precisely aligning and clamping the fractured pieces. A series of holes are drilled perpendicular to the crack and then shaped to accept interlocking metal keys. These keys are inserted, followed by studs driven into the holes, each stud biting into the preceding one to create a tight, secure join. Finally, the studs and keys are ground smooth for a polished finish. This method avoids the use of heat.

(ii) TIG (Tungsten Inert Gas Welding): TIG welding uses a non-consumable tungsten electrode and an inert shielding gas (Argon or Helium) to protect the weld from atmospheric contamination. A filler metal is often, but not always, used. A constant-current power supply creates an arc, ionising the gas and metal vapour to fuse the materials. TIG welding is ideal for thin sections of stainless steel and non-ferrous metals like aluminium, magnesium, and copper alloys. It produces high-quality welds but is slower and more complex than other methods.

MIG (Metal Inert Gas Welding): MIG welding uses a consumable wire electrode that melts and fuses with the workpiece material. A shielding gas is also used to protect the weld. Both AC and DC currents can be employed. MIG welding is suitable for steel, aluminium, and other non-ferrous materials. Its advantages include faster welding speed and easier automation.

THERMODYNAMIC CYCLE OF THE SHIPBOARD AIR CONDITIONING SYSTEM AND LOADING MECHANISMS

Shipboard air conditioning (AC) units use the vapour-compression refrigeration cycle with R134a, R407C, R410A or similar refrigerant (older plant R22). The cycle comprises four processes:

• Compression (1-2): Low-pressure refrigerant vapour from the evaporator enters the compressor where it is compressed adiabatically to a high pressure and temperature, becoming superheated vapour.
• Condensation (2-3): The hot high-pressure vapour passes to the condenser, where it is cooled by sea water (or chilled water/air) and condenses to high-pressure liquid, rejecting heat to the cooling medium.
• Expansion (3-4): The high-pressure liquid passes through the thermostatic expansion valve (or orifice), an isenthalpic throttling process in which pressure and temperature drop sharply, producing a cold mixture of liquid and flash vapour.
• Evaporation (4-1): The cold refrigerant absorbs heat from the air blown through the evaporator (heat is taken from the air), boiling/latent heat absorption, so the air is cooled and the refrigerant leaves as low-pressure vapour to re-enter the compressor.

The compressor continually circulates refrigerant, transferring heat from the cooled space (evaporator air side) to the sea water at the condenser.

Key components and functions

• Compressor: Raises refrigerant pressure and provides the driving circulation; may be reciprocating, scroll or screw type.
• Condenser: Rejects heat; sea-water cooled shell-and-tube or plate type.
• Expansion valve (TX valve): Throttles refrigerant, controls the degree of superheat at evaporator outlet and regulates refrigerant flow to match cooling load.
• Evaporator: Direct-expansion air-cooling coil (or chilled-water/brine system) where refrigerant absorbs heat from the air.
• Thermostats, HP/LP cut-outs, solenoid shut-off valves and capacity-control devices complete the plant.

Cooling load on the compressor (heat to be removed from the plant spaces) varies with ambient conditions, passenger complement, solar gain and external heat. To avoid the compressor over-refrigerating (cycling frequently) or running inefficiently, the following mechanisms are used:

• Capacity (unloader) control: On multi-cylinder reciprocating compressors, capacity control by loading/unloading cylinders - a solenoid valve admits discharge pressure to hold the suction valves open on selected cylinders, so those cylinders do not compress gas (reducing effective capacity), while the remaining cylinders carry the load. Loading restores full cylinder operation when demand returns.
• Hot gas bypass / cylinder unloading by means of a valve: Bypasses a controlled amount of gas from discharge to suction, unloading the compressor while it continues to run.
• Multiple compressors operating in sequence: Starting and stopping individual compressors or loading successive machines to match total load.
• Expansion valve regulation: The TX valve continuously modulates refrigerant flow so the plant tracks the evaporator load; as load falls the valve closes, and as it rises the valve opens, maintaining the set superheat and efficient evaporator usage.
• Thermostatic on/off control on smaller plant: A thermostat cycles the compressor, unloading it (stopping) at the set-point.
• Speed control (Variable Frequency Drive) on screw/centrifugal compressors: Adjusts compressor speed to match the load, providing the most energy-efficient part-load operation.
• Water-flow and brine-temperature control: Modulating chilled water/brine flow or chilled water temperature set-point adjusts the cooling delivered to the spaces.

By properly matching compressor capacity and refrigerant flow to the cooling load, the system maintains steady space temperature and humidity, avoids excess cycling, saves power and protects the machine.

Main Turbine Lubricating Oil System

Tin oxide corrosion occurs mainly on tin-based white-metal (Babbitt) bearing surfaces, particularly when there is water or salt-water contamination, combined with high temperature and pressure.

Effects

Formation of a hard oxide film

• A black or dark-brown oxide film forms on the white-metal bearing surface. Unlike normal Babbitt, this oxide layer is very hard.

Loss of embedability

• The hard oxide layer destroys the embedability of the white metal. As a result, dirt and wear particles can no longer become safely embedded in the soft bearing surface.

Reduction in bearing clearance

• The oxide layer builds up on the bearing surface and reduces the bearing clearance, interfering with the formation and maintenance of the proper lubricating oil film.

Abrasive damage from detached oxide particles

• Pieces of the hard oxide layer may break away and circulate with the lubricating oil. These particles can cause abrasive scoring of the thrust collar/journal and other bearings.

Overheating and bearing failure

• The disturbed oil film can cause local overheating, wiping and eventual bearing seizure or failure. In a thrust bearing, detached oxide particles may become trapped in the oil wedge, further restricting the oil film and causing overheating.

Main Causes

The important causes to consider are:

• Water or salt-water contamination of the lubricating oil
• Presence of chlorides
• High bearing temperature and/or load
• Unsuitable lubricating oil or additives

If tin oxide corrosion is detected in the high-pressure (HP) turbine thrust bearing, the following actions should be taken:

Reduce or stop the turbine as necessary

• Reduce the turbine load or stop the turbine as required by the manufacturer's instructions to prevent further bearing damage. Closely monitor the thrust-bearing temperature and lubricating-oil pressure.

Inspect the thrust bearing and pads

• Inspect the thrust bearing and pads to determine the extent of tin-oxide formation. Also check the thrust collar/runner for scoring or other damage.

Drain and replace contaminated oil

• Drain the contaminated lubricating oil and replace it with clean oil. The source of water or salt-water contamination must be identified and eliminated.

Thoroughly clean and flush the complete oil system

• Clean and flush the bearing housing, oil reservoir, oil lines and associated lubricating-oil system to remove tin-oxide particles and other contamination.

Renew damaged components and check clearances/alignment

• Renew badly affected thrust pads and repair or replace any damaged thrust collar/runner. Check the bearing clearances and alignment before returning the turbine to service. Lowering the oil temperature may also help prevent further formation of tin oxide.

Important Point

Simply scraping or polishing the visible black deposit is not sufficient. The complete lubricating-oil system must be cleaned and flushed because detached hard oxide particles may remain in the system and continue to cause abrasive damage.

The filtration size is not selected simply to obtain the finest possible filtration. It is selected according to the component being protected, required oil cleanliness, and the flow and pressure characteristics of the system.

1. Bearing Clearances

The filter must be capable of removing particles that are large enough to damage the journal or thrust-bearing oil film.

Therefore, smaller bearing clearances require finer filtration.

2. Type and Sensitivity of the Component

Different components have different tolerances and sensitivity to contamination. These may include:

• Main turbine journal and thrust bearings
• Reduction gears
• Hydraulic and governing equipment
• Servo and control valves

Precision hydraulic and control components generally require finer filtration than large and more robust components.

3. Minimum Oil Passage or Orifice Size

The filter must prevent particles large enough to block small drilled passages, restrictors and orifices from reaching these components.

Turbine lubricating-oil systems contain many relatively small oil passages, which can readily become blocked by contamination.

4. Required Oil Cleanliness

The required oil cleanliness level, such as the specified NAS or ISO cleanliness level, determines the degree of filtration required.

Turbine oils are generally maintained to very high cleanliness standards because contamination can cause damage to bearings and control systems.

5. Oil Flow and Permissible Pressure Drop

A very fine filter provides better particle removal, but it also produces a greater pressure drop and may become blocked more quickly.

Therefore, the selected filter size must be compatible with:

• The required oil flow
• The allowable differential pressure
• The expected contamination level

The filter must not restrict the oil supply to the machinery.

6. Location and Purpose of the Filter

Filters at different locations in the lubricating-oil system may have different filtration requirements:

• Pump suction/strainers: Relatively coarse, mainly to protect the pump.
• Main LO supply: Finer filtration to protect the turbine bearings.
• Control/governor/servo oil: Often still finer because of the small clearances and sensitive valves.
• Oil purification/off-line filtration: Can use very fine filtration because it is not necessarily restricted by the full operating oil flow.

Overall Principle

The filtration should be as fine as necessary to protect the most sensitive downstream component, but not so fine that excessive pressure drop or premature filter blockage compromises the lubricating-oil supply.

For this reason, turbine filter elements are available in different mesh and micron sizes, allowing the filtration level to be selected according to the requirements of each part of the system.

(a) Plate type heat exchanger:

A plate type cooler is a compact and highly efficient heat exchanger used on ships to transfer heat between two fluids—typically fresh water, lubricating oil, or seawater—without allowing them to mix.

It works on the principle of counterflow or crossflow heat exchange, where thin metallic plates separate the two fluids.

• One fluid flows along one side of each plate while the other flows along the opposite side.
• The large surface area of the plates allows efficient thermal energy transfer through conduction and convection.
• The corrugation or wavy pattern of the plates promotes turbulence, which enhances the rate of heat transfer and minimizes fouling.

Main Components:

1. Plates:
   • Thin, corrugated metal sheets forming the main heat transfer surface.
   • Corrugations increase turbulence and improve heat transfer efficiency.
2. Frame:
   • Provides structural support and holds all plates tightly together.
   • Maintains pressure and prevents leakage between the plates.
3. Gaskets (Packings):
   • Rubber or synthetic seals placed between plates.
   • Prevent fluid mixing and direct the flow through alternate channels.
4. Inlet and Outlet Ports:
   • Separate connections for the entry and exit of hot and cold fluids.
   • Arranged alternately for counterflow or crossflow operation.
5. Tightening Bolts:
   • Used to compress and secure the plates, ensuring proper sealing and pressure integrity.

Differences from Other Types of Heat Exchangers on Ships

Applications:

Plate type coolers are widely used on ships for:

• Lubricating oil cooling
• Freshwater cooling
• Central cooling systems

Advantages of Plate Coolers on Ships:

• Higher thermal efficiency.
• Smaller footprint and lighter weight (critical for ship space).
• Easier to clean and maintain, making them ideal for systems like lubricating oil coolers and freshwater central coolers.

TURBOCHARGER OVERHAUL RESULTING IN LOW SCAVENGE AIR PRESSURE AND LOSS OF POWER

1. Faulty turbine/ compressor overhaul - e.g. incorrect assembly, wrong clearances, misalignment of the rotor. Reason: increased internal friction/leakage reduces efficiency.
2. Damaged or incorrectly fitted blade profiles, or damaged nozzle ring. Reason: poor gas flow to the turbine reduces the power produced by the turbine.
3. Worn or incorrectly set bearings - journal/thrust clearance too big or too small causing the rotor to rub or to vibrate. Reason: vibration and rubbing destroy performance.
4. Rotor/ shaft out of balance or bent. Reason: increased vibration, seal damage and reduced speed.
5. Plugged or incorrectly refitted turbine gas inlet/outlet (exhaust duct or nozzle ring), or a closed/partly closed exhaust gas by-pass valve. Reason: reduced gas flow.
6. Leakage at the gas inlet/outlet joints or the blower casing - air leaks back to atmosphere or from the discharge. Reason: lost scavenge air.
7. Dirty/ fouled compressor or turbine blading (after overhaul unit not cleaned). Reason: reduced flow efficiency.
8. Damaged or incorrectly fitted labyrinth/ piston ring seals allowing air or gas leakage between compartments.
9. Incorrect rotor end clearances set at overhaul, causing rubbing of wheel to casing.
10. The air filter or cooler was disturbed/ blocked during the overhaul and not replaced; restricted suction raises pressure drop and lowers delivery.
11. Compressor surge or surging outlet pressure due to engine/charging system condition (e.g. a dirty scavenge cooler, exhaust back pressure) - this is a charging-system cause rather than the T/C itself.

1. Exhaust temperatures before and after the turbine (per cylinder and average). Reason: high turbine inlet temperature with low boost shows poor turbine gas flow/efficiency; uneven temps indicate cylinder problems.
2. Turbocharger speed (rpm) and boost pressure (scavenge/charge air pressure) at set loads. Reason: a speed that is low with normal exhaust back pressure shows a turbine/compressor fault; ratio of boost to rpm indicates compressor efficiency.
3. Compressor delivery temperature relative to speed. Reason: indicates compressor efficiency/fouling or leakage.
4. Charge-air cooler temperature drop (air before/after cooler) and sea water delta-T. Reason: an inefficient/warm cooler lowers charge air density and boost; shows whether the cooler was disturbed at overhaul.
5. Cylinder compression and firing pressures (indicator diagrams) and max combustion pressure at the load. Reason: confirms whether the loss of power is due to low scavenge pressure or to a fuel/cylinder fault.
6. Exhaust gas back pressure downstream of the turbine (after-turbine pressure). Reason: indicates system restrictions (exhaust boiler) that load the turbine.
7. Electronic engine management/ process data (if fitted): scavenge receiver pressure valve, T/C speed, temps logged against engine load and fuel index.
8. Lubricating oil pressure/temp to T/C bearings and condition (debris). Reason: indicates bearing fault or misalignment vibration.
9. Air filter differential pressure. Reason: a choked filter reduces compressor suction.
10. Fuel index/rack position versus rpm at set load. Reason: a higher fuel index to hold the same power shows lost charging efficiency.

1. Use only the maker's manual, correct clearances and locking/torque values; follow the OEM procedure step by step.
2. Record all as-found and as-fitted clearances (bearings, seals, end/axial float) and component serial numbers on the overhaul record sheet.
3. Balance the rotor as a complete unit (or per maker) and record the balance report; never swap or individual-balance wheels without a rig.
4. Clean both air and gas sides thoroughly with approved methods; avoid wire brushing that damages blade surfaces.
5. Renew all gaskets, O-rings, joints and locking devices on re-assembly; use new components where the manual requires.
6. Check nozzle ring, diffuser, blade profile and rotor fretting; renew damaged parts rather than refitting.
7. Reset and verify correct axial/radial clearances and rotor end-fits before final torquing.
8. Ensure correct lubrication - clean oil, correct pressure and flow, and a primed oil system before run-up.
9. Pre-commission: check free rotation by hand, check for rubbing, confirm rotation direction, and perform a slow run-up checking vibration, speed and boost against recorded values.
10. Perform a post-overhaul performance comparison (speed, boost, temps) against the baseline and initialise a fresh trend record.
11. Involve a qualified second engineer/officer to check the work, and follow a completed job-observation/release-to-operation procedure.
12. Keep proper records of the overhaul and of any abnormal findings so future work is carried out in a consistent manner.

Sketch of Stuffing box:

Overhauling the stuffing box of a two-stroke engine without removing the piston

Safety Measures:

• Ensure the engine is shut down and properly immobilized.
• Engage turning gear to prevent any unintended movement.
• Open the indicator cocks
• Display appropriate safety signage to inform personnel of ongoing maintenance.
• Stop the lubrication oil pumps.
• Inform the bridge and obtain propeller clearance to ensure the vessel remains stationary during maintenance.
• Ensure all personnel are aware of the maintenance activities to prevent accidental interference.
• Open crankcase doors and ventilate the area to disperse any hazardous gases.
• Arrange adequate lighting, including explosion-proof lamps and torches, to ensure clear visibility.
• Wear appropriate safety gear, including gloves, safety glasses, and protective clothing, to safeguard against injuries.

Tools Required:

• Specialized stuffing box extraction tool or puller.
• Torque wrench for precise tightening.
• Feeler gauges to measure clearances.
• Cleaning brushes and lint-free cloths for cleaning components.
• New sealing rings and gaskets as per manufacturer specifications.
• Lubricants compatible with engine components.

Removing the stuffing box:

• Position a worktable around the piston rod, ensuring it is securely mounted.
• This setup allows for the loosening of the remaining screws in the stuffing box flange through designated holes in the worktable.
• Through the access holes in the worktable, carefully loosen and remove the screws securing the stuffing box flange.
• Ensure all fasteners are accounted for to prevent any from falling into the crankcase.
• With the flange screws removed, gently lower the stuffing box from its position on the piston rod.
• Exercise caution to avoid damaging the piston rod or adjacent components during removal.

Cleaning:

• Thoroughly clean the stuffing box components to remove any accumulated oil, carbon deposits, or debris.
• Examine the stuffing box for signs of wear, damage, or deformation.
• Check sealing rings, scraper rings, and other critical parts for integrity.

Replacement:

• Replace any worn or damaged components with new parts that meet manufacturer specifications.

Reinstallation:

• Carefully position the refurbished or new stuffing box onto the piston rod, aligning it correctly with the mounting flange.
• Reinsert and tighten the flange screws through the worktable access holes, ensuring even torque is applied to maintain proper sealing.
• Reconnect and fill the lubrication system, checking for proper flow to the stuffing box.
• Manually rotate the engine using the turning gear to verify the smooth operation of the piston rod through the stuffing box.
• Inspect for any signs of oil or air leaks around the stuffing box area, addressing any issues before returning the engine to service.

A crankshaft's twist is assessed by examining witness marks. Before installation, these marks are etched onto both the crankshaft journal and the mating crank web. The interference fit between these parts (approximately 1/570 to 1/600) creates a compressive load of about 77 MN/m². If the crankshaft experiences an extreme load (e.g., sudden engine stall, starting with a liquid-filled cylinder, or bottom-end bearing failure), the journal might slip on the web. Misalignment of the witness marks indicates the degree of twist.

Twisting typically occurs at the journal-to-web interface, especially under extreme loads or impacts.

• Engine stalling: A sudden stoppage at full speed, such as when the propeller is jammed during grounding.
• Hydraulic Lock: Attempting to start the engine with a cylinder full of liquid, leading to excessive pressure on the crankshaft.
• Bearing Failures: A bottom-end bearing failure can result in obstruction, causing stress and twisting at the crankpin.

The location and extent of twisting depend on the affected unit:

• If slippage occurs at the web closest to the timing wheel, all units are impacted.
• If it happens further along the crankshaft (e.g., near Unit 2), only the adjacent units (e.g., Unit 1 and Unit 2) may be affected.

Up to 5° of twist might be tolerable without correction. This is due to the overlap in the air start timing, although, fuel pump and exhaust valve timing will be slightly affected. Small slippages can be accommodated by hydraulically adjusting the camshaft to correct the timing. However, any slippage must be carefully monitored to ensure it doesn't increase.

If twisting is minor (≤5°):

• Adjust Camshaft Timing: Realign the camshaft hydraulically to restore proper fuel pump and exhaust valve timing.

If twisting is excessive (>5°):

Jacking the Crankshaft:

• Turn the engine until the affected web is horizontal.
• Place a wooden plank beneath the crankshaft and position a hydraulic jack between the web and the plank.
• Remove the main bearing cover and top shell of the affected journal.
• Cool the journal using dry ice and heat the web to expand it.
• After sufficient preparation, reassemble the main bearing shells (without shims) and tighten the bearing cover.
• Gradually increase the hydraulic jack pressure to rotate the web back into alignment.

Monitor the process carefully to avoid sudden movements where the web may overshoot the original witness marks. Overshooting indicates that the shrink fit is compromised, which necessitates crankshaft replacement.

If the twisting is irreparable, or if the shrink fit is damaged during the adjustment process, the crankshaft must be replaced.

Replacement of a Jerk Type Fuel Pump

1. Jerk Type Fuel Pump – Description

The jerk type helix-port controlled fuel pump is widely used on slow-speed and medium-speed marine diesel engines.

The quantity of fuel injected and the end of injection are controlled by the helical groove on the plunger, which uncovers the spill port in the barrel.

The beginning of injection is determined solely by the plunger lift, which depends on the cam profile.

2. Safety Precautions Before Replacement

Before replacing the fuel pump, the following safety measures are taken:

• Engine stopped and turning gear engaged
• Starting air supply shut off and blocked
• Fuel oil and lubricating oil supplies isolated
• Indicator cocks opened
• Fuel pressure released and fuel oil drained before dismantling

3. Initial Setting and Governor / VIT Connections

• Existing fuel rack position is marked before dismantling
• Initial fuel rack index is checked and marked using the manufacturer’s template
• The cross-bore of the plunger is aligned with the lower cut-off holes in the barrel
• Alignment is confirmed by visual inspection or using a torch light
• Governor fuel rack linkage is disconnected only after marking its position
• If Variable Injection Timing (VIT) is fitted:
  • VIT index arm is pulled to zero position
  • Linkage position is clearly marked before disconnection

  4. Replacement Procedure of Jerk Type Fuel Pump

  • Fuel pump top cover is removed
  • Barrel and plunger assembly is dismantled
  • Fuel inlet pipe is disconnected
  • Nuts at the pump base are removed
  • Pump housing is lifted using approved lifting tools
  • Spare fuel pump assembly is fitted in position
  • Free movement of fuel rack is checked
  • Pump is aligned and tightened to the base
  • Fuel rack zero setting and calibration are carried out
  • Governor and VIT connections are reconnected and matched with initial markings

  5. Adjustment of Actual and Effective Stroke

  The timing of a jerk type fuel pump is measured by fuel pump lead.

  (a) Actual Stroke Adjustment

  • Achieved by turning the fuel cam disc
  • A change of 1 mm in fuel pump lead alters the peak cylinder pressure by approximately 3.5 bar

  (b) Effective Stroke Adjustment

  • Achieved by adding or removing shims between the pump housing and top cover
  • Each shim changes peak pressure by approximately 1.75 bar

  6. Common Faults and Their Effect on Engine Performance

  Fault	Effect on Engine Performance
  Worn plunger and barrel	Increased leakage, higher fuel index required for same load, reduced engine power
  Incorrect timing	Uneven peak pressures, inefficient combustion, increased thermal loading
  Defective suction / puncture valve	Low injection pressure, unit misfires, low exhaust gas temperature
  Cavitation damage	Erosion near helix edge, unstable and irregular fuel delivery
  Fuel leakage into camshaft space	Deterioration of lubricating oil quality and pressure
  Plunger seizure	Sudden loss of fuel supply, risk of severe engine damage

  Prompt attention is essential to prevent:

  • Power imbalance between cylinders
  • Excessive thermal and mechanical stress
  • Progressive component damage
  • Possible serious engine failure

Working principle

• Both are impulse/reaction turbines converting fluid energy (steam or exhaust gas) into shaft rotation. Cargo pump turbines are steam turbines (impulse or impulse-reaction) driving centrifugal cargo pumps on tankers; turbocharger turbines are exhaust-gas-driven turbines mounted on the main engine to drive an air compressor (blower).

Applications

• Cargo oil pump turbine: Drives a large centrifugal pump that discharges crude oil/ cargo. It runs on steam (from auxiliary boiler/exhaust gas boiler), typically at a fixed high speed available via reduction gearing to the pump shaft, and is reversible in some designs or uses a fixed rotation direction with the pump handling suction/discharge.
• Turbocharger turbine: Acts on the engine's exhaust gas to compress scavenge/charge air fed to the engine cylinders; it is an integral part of the engine's charging system and its speed varies continuously with engine load.

Design and operational differences

• Driving fluid: Cargo turbine uses dry saturated or superheated steam (constant supply pressure, ~7-17 bar); T/C uses variable-temperature exhaust gas (typically 250-500 C) from the engine.
• Speed: Cargo tur-bine runs at a relatively constant governed speed (around 2500-6000 rpm) driving via reduction gear; the T/C runs at 10,000-50,000 rpm, floating on engine load with no mechanical connection to a fixed load shaft.
• Mechanical connection: Cargo turbine has reduction gearing to a large low-speed pump; the T/C rotor is a single high-speed spindle with the compressor wheel on the same shaft.
• Blade design: Cargo turbine impulse blading for constant-pressure steam with power control; T/C has radial-flow compressor and axial-flow turbine blading optimised for the exhaust gas flow and for variable conditions.
• Control: Cargo turbine is controlled by steam throttle valves, governing to set the pump speed/ discharge pressure; the T/C is self-regulating matching its speed to the engine gas flow (with a waste gate/ by-pass on some designs to limit speed/boost at high load).
• Requirements: Cargo turbine must be robust in a cargo-pump room, withstand steam conditions, be smooth and reversible if required, and be capable of continuous heavy duty; the T/C must be highly efficient, compact, low inertia (rapid acceleration), heat-resistant, and oil-cooled to survive high speed and temperatures.

1. Throttle (steam admission) control: Varying the opening of the main/nominal stop and manoeuvring throttle valve admits more or less steam to the nozzles; more steam = more power and higher speed, less steam = lower speed. This is the primary method to set pump speed.
2. Nozzle group (nozzle control) valves: A set of independently operated nozzle valves admits steam to groups of nozzles in stages, giving efficient part-load control by adjusting the active nozzle area.
3. Governing valve on the reduction/gland or trip/ emergency overspeed: a speed governor adjusts steam admission automatically to hold a set speed as cargo discharge conditions (backpressure) change.
4. Reversing manoeuvring valve on reversible machines: Admits steam to the astern nozzle direction to reverse the rotation where pump is required to operate astern.
5. External variable-speed drive (where fitted, e.g. hydraulic coupling or VFD on turbo-generator pumps): adjusts pump speed. For conventional cargo turbines, throttle/nozzle governing is the method used.
6. By manipulating the discharge/ suction valve on the pump and the sea/cargo line so the pump operates on its curve - adjusting flow and hence required power, but the actual turbine speed is set by steam admission and governor.

Precision control of cargo operations is achieved because the turbine speed governs pump discharge pressure and flow; accurate throttle and nozzle settings together with the speed governor give stable control of cargo handling (loading, discharging, stripping and tank cleaning) at the required rates.

The vacuum condenser is part of the main condenser/ vacuum system serving the main cargo steam-turbine-driven pumps (and the turbine-alternator). Its role is to condense the exhaust steam from the turbines back to condensate (clean water) so it can be returned to the boiler and reused, maintaining a closed steam/condensate circuit. By creating a vacuum in the condenser (via eductor/hotwell vacuum or the air ejector), the backpressure on the turbine exhaust is lowered, which increases the turbine's efficiency and power output and reduces steam consumption. The condenser also protects the turbine from backpressure damage and recovers condensate, conserving water. It contributes to efficiency by enabling the turbines to develop the required power with less steam (better economy), and to safety by maintaining a proper steam/ condensate balance to the boiler, preventing the cargo operations from being interrupted by loss of vacuum or by contaminated/carry-over condensate, and preventing hot steam blow-through. The vacuum system (air ejector, eductor) removes air and incondensables to hold the vacuum.

INSPECTION OF A CROSSHEAD BEARING (CSM survey)

1. Preparation and safety: Stop the engine, secure the turning gear/barring and isolate it, drain lubricating oil, blank off any pressurised source, and obtain the maker's overhaul manual. Prepare a work/risk assessment and tooling, and lift the unit to a position where the crosshead pin is accessible.
2. Lift the piston and crosshead: Remove the cylinder cover and piston as a unit to give access to the crosshead bearing (bearing is usually inside the crosshead, under the piston rod clamp). The piston is lifted clear and supported.
3. Clean the bearing: Drain the oil; clean the bearing cap, shells and the crosshead pin with a clean cloth/dry cleaning solvent (paraffin) and inspect.
4. Visual inspection: Examine the white-metal (bearing) surfaces for cracks, pitting, wiping, scuffing, scoring, overheating (discoloration), and looseness of the white metal from the shell (detect by tapping). Check the shell seating, the dowels/ locating lugs and the bolt/ stud condition.
5. Measurement of clearances: Measure the bearing clearance (diametral) using a feeler gauge at the parting faces, or use the maker's clearance gauge, plastigage / lead-wire method, and record against the specified limits. Record upper/lower.
6. Check bolt torque and stretch: Confirm the bearing bolts are at the maker's torque and measure bolt stretch/ elongation as applicable.
7. Inspect the crosshead pin and its fillets: Check for scoring, pitting and cracks (dye-penetrant or magnetic particle check on the fillet radius); measure the journal diameter for wear/ out-of-round.
8. Inspect the oil ways and feed holes: Ensure the crosshead pin oil holes and the bearing supply drillings are clear and clean.
9. Check the bearing shells alignment to the pin by bluing/ contact marking (the shell bore should contact evenly).
10. Record all readings and findings on the survey/overhaul sheet (clearances, defects, measurements) for trend comparison.

• Isolate and secure the barring gear; tag the engine not-to-run.
• Use correct lifting gear and properly sling the piston/crosshead; secure against swinging.
• Keep the working area clean, dry and well lit; observe oil/ chemical hygiene.
• Protect precision surfaces (pin, shell, filter faces) from damage and contamination.
• Handle the white-metal shells carefully - they are soft and easily damaged.
• Never re-use damaged or distorted bolts; use genuine spares and correct tooling.
• Use the correct torque wrench setting and sequence; check bolt stretch.
• Keep fuel/ oil away from heat or ignition sources, and use the correct PPE.

• Overheating/ wiping of white metal: from oil starvation, excessive clearance, overloading, or misalignment. Rectify: renew the shell, correct clearance/supply.
• Cracking/ sinking of white metal: fatigue from cyclic loading and/or poor shell seating. Rectify: renew shell, check seating.
• Scoring/galling: from contamination (dirt, abrasive), oil starvation, or misalignment. Rectify: clean system, renew shell, check oil filter and clearance.
• Pitting: from water/ acid in the oil or cavitation. Rectify: address oil condition, renew shell.
• Loose shells (shell not seating/ hammering): from incorrect clearances, fretting of the shell back or damaged locating lugs. Rectify: renew shell, repair lugs.
• Excessive clearance: from normal wear. Rectify: renew/stim shims to restore the clearance range.
• Seizure of bearing: from severe oil failure; engine may have suffered consequential damage - renew bearing and fully investigate.

• Confirm the bearing clearance is to specification (feeler/plastigage) and record.
• Torque the bolts to specification and check bolt stretch.
• Carry out an oil-flow/ priming check: turn on the lubricating oil, allowing oil to reach the crosshead bearing and confirm oil is discharged from the feeds.
• Bar the engine several revolutions by turning gear to confirm free rotation and no tight spots or binding.
• Re-run the engine at low rpm initially and check for abnormal noise, temperature rise of the bearing, and oil pressure/temperature.
• Perform a full power run and monitor bearing temperature and vibration; confirm no excessive heating.
• Verify the securing/locking of all bolts and oil connections.

A high concentration of iron in the oil sample suggests excessive wear of ferrous engine parts. Likely sources include piston rings, cylinder liners, crankshaft, camshaft, gears, or oil pump components. The wear may arise from abrasion, corrosion, or inadequate lubrication, and if left unchecked, can progress to major engine failure.

Subsequent Investigation:

1. Wear Metal Analysis – Perform detailed analysis to identify wear patterns and correlate with maintenance history.
2. Engine Component Inspection – Visually inspect piston rings, liners, crankshaft, bearings, gears, and pump components, paying attention to surface finish and wear patterns.
3. Lubrication System Assessment – Verify oil pressure, oil delivery, and filtration efficiency.
4. Oil Sampling Frequency – Increase sampling interval to closely monitor progression of wear.

The combined presence of copper, antimony, and tin is a strong indicator of bearing material degradation. Bearings and bushings in diesel engines are typically made of copper-based alloys or white metal (tin and antimony). Their simultaneous detection points to accelerated bearing wear, possible lubrication issues, or contamination.

Subsequent Investigation:

1. Bearing and Bushing Inspection – Check journal bearings, main bearings, connecting rod bearings, bottom-end bearings, crosshead bearings (if applicable), thrust washers, and bushes for scoring, fatigue, or failure.
2. Measurement of Clearances – Take accurate clearance readings to assess the extent of bearing wear.
3. Source Determination – Distinguish between normal running-in wear and abnormal wear due to lubrication failure or contamination.
4. Maintenance History Review – Check for recent overhauls or bearing replacements, as premature failure of new parts could be the cause.

Silicon in oil indicates contamination, commonly from dirt, dust, or sand ingress through the air intake, or from silicone-based gasket/sealant material leaching into the oil. This contamination is dangerous as it introduces abrasives that accelerate liner, ring, and bearing wear.

Subsequent Investigation:

1. Air Filter and Breather Pipe Inspection – Check for damaged, clogged, or improperly seated filters; replace if necessary.
2. Seal and Gasket Integrity – Inspect all air intake joints, turbocharger seals, and gaskets for cracks, leaks, or poor fitment.
3. Environmental Review – Assess whether the engine operates in a dusty environment, and if so, introduce stricter filtration measures or more frequent filter changes.
4. Oil Sample Particulate Analysis – Differentiate between silica dust contamination (external) and silicone sealant degradation (internal).

In summary:

• Iron → Points to wear of ferrous engine parts → Inspect liners, rings, crankshaft, and lubrication system.
• Copper, Antimony, Tin → Indicates bearing material wear → Inspect bearings, measure clearances, and review lubrication/maintenance.
• Silicon → Sign of contamination from dust/sealants → Check air filtration, seals, and environment.

(i) Pneumatic control equipment

Reliability

Pneumatic systems are highly reliable and rugged, frequently used for control and automation in ship engines and auxiliary systems. Since they operate using compressed air, they present no fire or electrical hazard. They function well despite the typical engine room conditions of vibration, humidity, and temperature variations.

Maintenance Requirements

Routine attention for pneumatic equipment focuses on maintaining the quality of the air supply and the integrity of the system components:

• Drainage: Regularly drain moisture and oil from air receivers and pipelines.
• Cleaning/Inspection: Clean and inspect filters, lubricators, and pressure regulators.
• Leak Check: Check for air leaks in pipes, connections, and actuators.
• Testing: Test solenoid-operated air valves for correct operation.
• Calibration: Periodically calibrate pressure sensors and transmitters.

Common Defects

Pneumatic systems are generally simple, dependable, and easily repaired onboard, requiring little specialized skill. Common defects include:

• Air Leaks from joints or diaphragms.
• Valve Sticking due to oil, dust, or corrosion.
• Sluggish Movement caused by moisture contamination.
• Pressure Fluctuation resulting from faulty compressors or regulators.

(ii) Electro-mechanical control equipment

Reliability

Electro-mechanical systems combine electrical signals and mechanical movement, exemplified by devices like contactors, relays, solenoids, governors, and limit switches. They are moderately reliable and are used in control circuits, alarms, and start/stop systems on ships. However, they are prone to wear because they incorporate moving parts.

Maintenance Requirements

Maintenance for these systems is critical for preventing mechanical wear and electrical faults:

• Cleaning: Regular cleaning of relay contacts and terminal connections.
• Lubrication: Lubrication of moving linkages or solenoids where required.
• Tightness Check: Check the tightness of electrical terminals to prevent arcing.
• Insulation Test: Perform insulation testing to detect moisture or degradation.
• Component Replacement: Promptly replace worn contact points or burnt relays.

Common Defects

The performance of electro-mechanical systems deteriorates with age and lack of attention. They require periodic inspection, cleaning, and replacement of worn parts.

• Contact Damage: Contact wear, pitting, or burning due to arcing.
• Coil Failure: Coil burnout in solenoids from overheating.
• Faulty Connections: Loose or corroded terminals causing intermittent faults.
• Mechanical Sticking: Mechanical sticking of relay arms or limit switches due to dirt or lack of lubrication.

(iii) Electronic control equipment

Reliability

Modern marine engines use microprocessor-based electronic systems for precise control of fuel injection, exhaust valves, alarms, and safety functions. They offer high efficiency and accuracy with a fast response and fewer moving parts. However, they are sensitive to environmental factors like heat, vibration, moisture, and electrical noise.

Maintenance Requirements

Maintenance is focused on providing a stable, clean environment and checking electrical integrity:

• Environmental Control: Keep control cabinets clean, cool, and dry; actively avoid condensation.
• Inspection: Inspect and clean connectors, sensors, and cables regularly.
• Electrical Check: Check power supply voltages and earthing connections.
• Diagnostics: Use built-in diagnostic tools to verify signal integrity and software performance.
• Replacement: Replace defective modules or sensors strictly as per manufacturer's instructions.

Common Defects

Due to their sensitive nature, defects often involve component failure or signal disruption:

• Sensor Failure: Failure of a sensor or transmitter (e.g., temperature, pressure, or speed).
• Connection Issues: Loose or corroded connectors causing intermittent faults.
• Component Damage: Printed circuit board (PCB) or chip damage due to overheating or voltage surge.
• Software Errors: Software communication or logic errors.

The routine attention required and common defects for each type of control equipment (Pneumatic, Electro-mechanical, and Electronic) have been discussed in detail under the 'Maintenance Requirements' and 'Common Defects' sections for parts (a)(i), (a)(ii), and (a)(iii) respectively.

involves conducting maintenance activities based on a fixed schedule, irrespective of the actual condition of the equipment.

Advantages:

• Regular inspections reduce the chances of unexpected breakdowns, improving operating efficiency.
• Maintenance can be scheduled at favorable times to avoid disruption of operations.
• Labour and spare parts are managed more efficiently, ensuring timely replacements.
• Scheduled maintenance ensures machinery operates safely and reliably.
• Services from the manufacturer or specialized technicians can be arranged in advance.

Disadvantages:

• Maintenance is performed whether or not it is necessary, leading to increased costs.
• Fixed schedules may not always align with the actual condition or wear of the machinery.
• Routine maintenance might inadvertently cause new failures due to human error or component misalignment.
• This system is most effective for equipment with predictable, age-related wear and tear.

uses real-time data from sensors and instruments to assess equipment condition and predict failures. Maintenance is performed only when data indicates a need.

Advantages:

• Reduces unnecessary maintenance, saving time, labor, and materials.
• Downtime is minimized, and equipment life is extended.
• Predicts and prevents catastrophic failures, ensuring operational safety.
• Enables detailed failure analysis to address underlying issues.
• Maintenance schedules can be optimized based on actual equipment conditions, reducing disruption.

Disadvantages:

• Requires sophisticated instruments and proper techniques for monitoring.
• Skilled personnel are necessary to interpret monitoring data accurately.
• Implementing monitoring systems involves high upfront costs.
• Requires time to collect sufficient data to assess trends accurately.

This policy involves replacing components at fixed intervals to address recurring problems, regardless of their actual condition.

Advantages:

• Effectively resolves recurring issues, ensuring reliability.
• Replacing inexpensive components is often economical and ensures reliability.

Disadvantages:

• Periodic replacement does not address the underlying cause of failures.
• Replacing large or critical parts can be costly and time-consuming.
• Replacing major components often requires significant downtime.
• Replacing components might introduce new issues unrelated to the current problem.

Each maintenance policy has specific applications depending on the operational requirements and nature of the machinery:

• Planned Maintenance: Best suited for predictable wear and tear but may involve unnecessary work.
• Condition Monitoring: Provides optimized and cost-effective maintenance but requires expertise and initial investment.
• Periodic Replacement: Solves recurring issues effectively but can be costly and may overlook root causes.

DETECTION AND REMEDY OF REFRIGERATION COMPRESSOR / MOTOR MISALIGNMENT

Detection of misalignment

1. Visual/rough check: with the coupling guard removed; a straight-edge across the two coupling halves (rims) will show angular misalignment; feel for unequal gaps around the circumference (face misalignment) and difference in radial position.
2. Feeler gauge and dial test indicator (DTI) method: Mount a dial indicator on one coupling half (rigidly) with the plunger bearing on the face and rim of the other half; rotate slowly and record total indicator reading (TIR). Radial TIR indicates parallel offset misalignment; face (axial) TIR indicates angular misalignment. Take readings at top, bottom and sides (0,90,180,270 deg) and at each 90 deg position to get a full picture.
3. Laser alignment (modern preferred method): A belt-driven or flange alignment laser kit (e.g. on motor-pump sets) measures accurate offset and angular values in both vertical and horizontal planes and gives shim/ moves. This is the most accurate for a large reciprocating compressor.
4. Operational symptoms of misalignment: excessive vibration, noise, overheating of the coupling/ bearings, rapid motor or compressor bearing wear, high current/amps, coupling wobble, or oil leakage; misalignment often shows as vibration at 1x rpm and as a machine that is hot but not overloaded.

Remedy

1. Stop the crane and isolate (electrical and mechanical), lock off, and remove the coupling guard.
2. Slacken the motor hold-down (foundation) bolts.
3. Using a dial/ laser alignment procedure, adjust the motor (or compressor) by shims (parallel shimming) to remove the vertical offset and angular misalignment, and move/pack to correct horizontal (side) misalignment.
4. Set the correct face gap (distance between coupling halves) to the maker's coupling specification, and correct the coupling to the machine's cold-alignment figures (accounting for thermal growth at operating temperature where specified).
5. Re-torque the foundation bolts evenly in sequence.
6. Re-check the alignment with the dial/laser and re-adjust until TIR is within manufacturer tolerance.
7. Re-fit the coupling (if split/removed), refit bolts/screws of the coupling to the correct torque, then refit the guard.
8. Record the alignment figures in the maintenance record for future reference and set a schedule to re-check alignment, especially after bedding-in or foundation work.

Note: If a large alignment change is required, also check the machine feet/foundation for soft-foot (using the dial/ laser to detect a resilient/ low foot) and pack accordingly, as soft-foot will distort the frame and cause repeat misalignment.

1. Preparation: With the vessel in dock and the rudder stock accessible, note the rudder angle and secure the rudder in the midship (or a marked) position; dewater and wash down the rudder and sternpost area.
2. External visual examination: Examine the rudder plating, welds and fairing for cracks, corrosion, pitting, wastage, buckling and deformation over the whole blade surface (both sides once access allows) and the edges; check the leading/trailing edges and the rudder palm/sole plate.
3. Check for flooding of a hollow rudder: Tap the rudder blade to detect a dead/ solid or hollow (half-empty) sound, weigh the rudder if provision is available, or use ultrasonic thickness; a hollow rudder is often detected by draining the rudder drain plug - water or air coming out indicates internal water/ flooding - or by internal inspection where an inspection cover exists.
4. Check the rudder stock: Expose the rudder stock at the palm/top; examine for corrosion, pitting, cracks (particularly at the palm weld and at the top of the blade), and check the rudder stock to hull gland for leakage and fretting.
5. Check the rudder carrier/gland and rudder seal: Examine the packing/gland for tightness, the lower and upper rudder carrier bearings and the stock support.
6. Check rudder pintles and gudgeons (with bearings): Remove/ lower or examine the pintles for wear, scoring, pitting and correct clearance; check the gudgeon pockets, and check the pintle/hinge line alignment; measure bearing clearances.
7. Check the rudder stock coupling/flange: Check bolts for tightness and the joint for fretting/corrosion; check the stop and the emergency-quadrant coupling.
8. Check rudder angle indicators/ tele-motor: Confirm the mechanical and electrical indication and the stops work; check the tiller/ quadrant and actuating linkage.
9. Check anti-singing and appendages, and check the rudder horns (if any), and the rudder to hull gap and freedom of movement.
10. Record all findings, measurements (wastage, clearances), and photography for the survey report and repair specification.

(i) Relief valve:

• Relief valves are fitted in the hydraulic system of a steering gear (or as specified) set to relieve at a pressure set to limit the pressure in the system to that which is safe, so as to prevent overloading/damage to the gear and to the hydraulic unit. SOLAS requires that relief valves be fitted on the arrangement to limit the pressure when the steering gear is stalled; the setting shall be not less than the max working pressure at which the steering gear is required to operate and not more than the nominal/ burst rating of the system; the valve must be so fitted that relief occurs without chattering and that the fluid escaping is returned to the header tank/reservoir. The valve capacity and set pressure must comply with the manufacturer/ Class approved values and the relief valve must be proved during testing.
• (Essentially: the relief valve protects the steering gear hydraulic system from over-pressure under stalled operation, set to a value between the operating pressure and the system safe limit, sized to pass the full pump flow, and returned to the oil header.)

(ii) Steering gear control:

• SOLAS requires that the main steering gear control and the auxiliary/emergency control be operated so that failure of one component does not make the other ineffective; they must be arranged so that a single failure in the control system (apart from the steering gear units) does not prevent both motor and the auxiliary from operating. The control system must be capable of being brought into operation quickly (within the required time, generally 45 seconds after failure at sea). The steering gear control system must have an audible and visual alarm on the navigating bridge for a component failure; redundancy is required (e.g. duplicated control circuits) so that a single failure in the control does not cause loss of all steering.
• Electric control: a failure of the controlling gear (controller) must not render the other ineffective; provisions for changeover between main and emergency control must be provided.

(iii) Electrical power circuits:

• SOLAS requires that the electrical power circuits of the steering gear be so arranged that a single fault in the power supply/power circuits of one steering gear will not cause a failure of the other; i.e., the power circuits to the two steering gear sets are fed from independent and duplicated power sources (main and emergency/ battery). The system must be fed such that the failure of one circuit (e.g. one motor circuit or one generator feeder) does not render the other steering gear set inoperative, and automatic switching/ reorganization ensures the steering remains available. Where a telemotor/ emergency steering is fitted, a separate independent power source is provided. SOLAS also specifies the number of power units and the time by which the emergency source must supply (e.g., 45 seconds) so the gear can be brought into operation.

• If a hotspot exists in the crankcase, some lube oil will come in contact with it and will be vaporised.
• The vapour will circulate to cooler parts of the crankcase and condense to form a white oil mist
• The oil droplets in this white mist are very small. If this oil mist circulates back to the hotspot in such concentration (with typical particle sizes of around 0.5 to 5 microns in diameter, density between 30 to 50 mg/L (milligrams per litre)), it will be ignited, and a primary explosion will occur.
• The explosion can cause a flame front and pressure wave to accelerate through the crankcase, vaporising further oil droplets in the path.
• The pressure shock wave may build up sufficiently to rupture crankcase doors if not relieved.
• If the relief valves do not reseal after lifting, it will cause fresh air to enter into the crankcase, resulting in another flammable mixture to be developed, leading to a secondary or major explosion.
  

• Modern engines often have sensors to monitor bearing temperatures.
• Feeling the crankcase door for excessive heat.
• Measuring the temperature of oil returning from bearings.
• Unusual sounds from the crankcase might indicate component wear or malfunction.
• A visible and dense mist from the breather pipe suggests significant oil vaporisation.
• Overheating can cause paint to peel or discolour on the crankcase or doors.
• Irregular running of engine

(c) Procedure in the event of overheating being evident

• In the event of overheating being evident, start the stand-by generator and
• Inform bridge, C/E and 2/E about the situation, if the vessel is not in navigational danger, stop the engine. This will help in cooling the hotspot.
• Evacuate all personnel from the engine room. This prevents injury to personnel if there is an explosion.
• Continue to run the lubricating oil pumps to help cool down the hotspot.
• Do not go near crankcase relief valves. This is to prevent injury in case there is an explosion.
• Wait at least 20 minutes before opening the crankcase doors. Allowing oxygen by opening the doors may cause an explosion.
• Isolate the engine (shut off start air, stop LO pumps, engage turning gear) this is to prevent accidental start
• Open crankcase doors and find the cause of overheating.
• Repair/ rectify the cause of overheating. This could be due to a bearing, chain rubbing, piston rod fouling on the stuffing box, cracked piston, etc. The engine should not be restarted until the cause is established and corrected.
• Before restarting, check the oil flow through the bearings, chains/ jet sprayers, and piston cooling return. Turn the engine and monitor the load on the turning gear motor (to check the engine is not binding on the tight spot)
• When restarting, keep a close eye on any repairs. Use an IR temperature gun to monitor the location of overheating. Stop the engine after 30 seconds, 2 minutes and 10 minutes running at low load and check for overheating. To prevent reoccurrence.
• Increase load over 2 hours, keeping a close eye on bearings temperature and oil mist detector.
• If the engine is fully operational, when the Chief Engineer is satisfied with the running of the engine, hand it back to bridge control.

However, the following measures ensure that the possibility of explosion is less:

• Ensure the OMD is correctly calibrated and alarms are set appropriately.
• Ensure the automation system slows the engine down when the OMD activates.
• Regularly inspect the crankcase for lubrication conditions and signs of overheating.
• Adhere strictly to the manufacturer's recommended maintenance schedules.
• Regularly check and clean relief valves and flame traps.
• Do not operate the engine beyond its designed capacity.
• Maintain adequate lubrication to minimise friction and heat generation.
• Ensure the bearing high-temperature alarm is functioning correctly.

(a) Procedure for Complete Inspection of a Bottom End Bearing:

Setting auxiliary boiler safety valves to lift at the desired pressure under steam is a critical procedure that ensures the safe operation of the boiler. The process typically involves the following steps:

1. Preparation:

   • Ensure the boiler is under steam and can be brought up to the desired set pressure. All other safety valves on the boiler (if multiple) should be gagged or secured to prevent them from lifting prematurely, allowing the focus to be on the valve being set.
   • The easing gear of the valve to be set should be checked for freedom of movement and then disengaged.
   • Ensure accurate pressure gauges are fitted and calibrated.

2. Initial Adjustment:

   • The compression screw (adjusting nut) on top of the safety valve, which controls the spring tension, is initially adjusted to a point where the valve is expected to lift below the desired set pressure.

3. Raising Pressure and Observation:

   • The boiler pressure is slowly and steadily raised by increasing the firing rate while monitoring the boiler pressure gauge.
   • As the pressure approaches the desired set pressure, observe the valve carefully. The valve should begin to 'feather' (emit a slight hiss of steam) just before it fully lifts.

4. Fine Adjustment of Lifting Pressure:

   • If the valve lifts below the desired pressure, the compression screw is tightened (turned clockwise) to increase the spring compression and thus the lifting pressure.
   • If the valve does not lift at the desired pressure, the compression screw is loosened (turned anti-clockwise) to decrease spring compression.
   • This adjustment is done incrementally, allowing the boiler pressure to fluctuate slightly and observing the valve's response. The aim is for the valve to lift cleanly and fully at the exact desired set pressure.

5. Blowdown Adjustment (if applicable):

   • Once the lifting pressure is set, the blowdown (the pressure drop before the valve reseats) is checked. This is typically adjusted by a blowdown ring or adjusting ring located around the valve seat. Adjusting this ring changes the escape area for the steam, influencing the pressure at which the valve reseats.
   • The blowdown should be within the manufacturer's specified limits or classification society requirements (e.g., 3-5% of set pressure).

6. Final Check and Securing:

   • After the lifting pressure and blowdown are correctly set, the lock nuts on the compression screw and blowdown ring (if adjustable externally) are securely tightened to prevent accidental movement.
   • The process is usually repeated for all safety valves, ensuring they lift sequentially at their designated pressures (e.g., one at maximum working pressure, the other slightly higher).

To ensure the integrity of the safety valve settings and prevent unauthorized tampering after completion, the following precautions are essential:

1. Lead Sealing: This is the primary method. Lead seals are applied to:

   • The compression screw (adjusting nut) and its lock nut, securing them to the valve spindle or yoke. This prevents alteration of the spring tension.
   • The blowdown adjusting ring (if externally adjustable) and its locking mechanism, to prevent changes to the blowdown pressure.
   • The easing gear mechanism, to ensure it cannot be used to manually lift the valve without breaking the seal.
   • The seals are typically stamped with the classification society's mark or the ship's official stamp.

2. Witnessing and Documentation:

   • The setting procedure is usually witnessed by a qualified classification society surveyor and/or the Chief Engineer.
   • Detailed records of the set pressures, blowdown, date of setting, and names of personnel involved are entered into the boiler logbook and official records.

3. Restricted Access:

   • Safety valves are typically located in the boiler room, which is a restricted access area on board, limiting opportunities for unauthorized personnel to interfere.

4. Regular Inspections:

   • During routine rounds and surveys, engineers and surveyors visually inspect the safety valves to ensure all seals are intact and show no signs of tampering.

The accumulation of pressure test, also known as the overpressure test or full capacity test, is a crucial test performed on boilers to verify the adequacy of their safety valve discharge capacity. Its primary purpose is to ensure that, under the most severe operating conditions, the safety valves can release steam quickly enough to prevent the boiler pressure from rising to a dangerous level.

Procedure:

1. The boiler is fired at its maximum continuous evaporation rate (maximum firing capacity).
2. All steam outlets from the boiler, including the main stop valve and auxiliary steam lines, are closed.
3. All safety valves on the boiler are allowed to lift and discharge steam simultaneously.
4. The test is continued for a specified duration, typically 7 minutes for water-tube boilers and 15 minutes for fire-tube boilers, or as per classification society requirements.

Acceptance Criteria: During the entire duration of the test, the boiler pressure must not rise by more than 10% above the maximum permissible working pressure (or the highest set pressure of any safety valve, whichever is greater). If the pressure rise exceeds this limit, it indicates that the safety valves do not have sufficient discharge capacity, and corrective action (e.g., increasing valve size, adding more valves, or reducing boiler firing rate) would be required.

Significance: This test is vital for confirming the design and operational integrity of the boiler and its safety system. It demonstrates that even if all steam demand ceases while the boiler is firing at full capacity, the safety valves can prevent catastrophic overpressure. It is typically performed during commissioning, after major repairs, and periodically during classification surveys, usually witnessed by a classification society surveyor.

ROCKING TEST OF DECK CRANE

What is the rocking test?

The rocking test (also called "rocking" of the slew/derrick or crane jib test) is a structural load test carried out on a deck crane (or derrick) to verify the integrity and safe working load of the crane's jib and the slew/ luffing structure. The crane jib is "rocked" (swung) under load through a controlled arc or the crane is loaded to a proof-load angle, and the deflections/ soundness of the structure are observed. It demonstrates that the crane will safely sustain its working load and that the structural members, welds, pivot and slew components are sound.

Procedure of the rocking test

1. Preparation: Ensure the crane is in good order, the area is clear of personnel, and the deck is clear below the crane. Check the safe working load (SWL), proof load, and the maker's test procedure; confirm the crane is secured/moored so the deck can accept the load.
2. Select the test load: hoist a certified test weight (typically the proof load = 1.25 x SWL, or as the maker/Class require) onto the head block; attach with correct slings.
3. Raise the load a short distance and check the hoist/ lowering brakes and that the crane holds.
4. Carry out the rocking motion: with the load suspended, the crane is slewed/luffed (rotated) through the extreme positions and rocked by applying the lowering/luffing brakes so the jib is alternately loaded and unloaded (rocking action) - this flexes the jib and slew structure, reproducing service fatigue loading.
5. Observe during rocking: watch for abnormal deflection, distortion, cracking sounds, permanent set of the jib, and inspect the pivot, heel pins, structural members and welds after rocking.
6. Measure and record deflections: take deflection readings at the jib head with a taut wire/ DTI before and during the test; compare against the maker's allowable deflection.
7. On completion: Lower and remove the load, re-examine the structure (welds/joints) for any new cracks or deformation, grease/re-secure as appropriate, and record the results on the test sheet.
8. Carry out the load test of the safety/load indicators and perform the electrical/hydraulic functionality checks (limit switches, pressure, etc.) as a final check.

Fault finding procedure (tabulated)

• Excessive deflection / jib sagging: damage/overload/worn pivot - check for permanent set; STOP test, relieve load, inspect.
• Cracking sound or visible crack: material fatigue/fracture - stop, empty the load, inspect with NDT (dye penetrant/Magnaflux).
• Slew does not move freely under load / binds: slew pin bearing worn or tight - stop, inspect bearing.
• Hoist/luffing grabs or slips: brake or overload issues - stop, inspect brakes/clutch.
• Hydraulic leaks/pressure drop on deck (if electro-hydraulic): oil seal / valve fault - stop, isolate, repair.
• No abnormal reading: healthy - record as passed.

Action if deviation out of limit

If the deflection or any observed parameter exceeds the maker's limit, stop the test immediately, relieve/remove the load, and the crane is withdrawn from service (tagged out-of-use, "DO NOT USE"). Investigate the cause - structural deformation, fatigue, or defective components - using NDT (magnetic particle/cracks), and report to the Chief Engineer/ machinery superintendent. The crane must not return to service until the defect is rectified (repair/renewal of the affected member/bearing), and a re-proof or re-test carried out to the maker's/Class requirements. A survey/ approval may be needed before returning to service.

When an exhaust valve body is seized in the cylinder head and its internal threads for the bellows connection are damaged, the removal becomes a complex "over-limit" maintenance task. The following procedure combines mechanical extraction techniques with heat-based and structural solutions:

1. Preparation and Safety

• Isolate the Engine: Ensure the main engine is properly "blocked" (stopped, starting air isolated, turning gear engaged, and "Work in Progress" tags posted).
• Drain Cooling Water: Drain the cylinder head cooling water to avoid thermal shock or contamination during heating operations.
• Clear the Area: Remove the exhaust bellows (if possible) and all peripheral piping to provide maximum workspace.

2. Initial Extraction Attempts (Non-Destructive)

• Penetrating Oil: Apply high-quality penetrating oil or "freeze-off" spray to the seating area and let it soak for several hours.
• Thermal Expansion (Differential Heating):
  • Carefully apply heat (using a rosebud torch) to the cylinder head surrounding the valve body to expand the bore.
  • Simultaneously, apply cooling (CO2 or ice) to the valve body itself to shrink it.
• Impact Loading: Use a heavy-duty slide hammer or a pneumatic hammer with a flat bit to create vibrations that may break the rust/carbon bond.

3. Addressing Damaged Internal Threads

Since the internal threads for the bellows connection are stripped, standard lifting tools cannot be used.

• Fabricate a Custom Puller: Use a "stud-and-bridge" arrangement. If the threads are gone, you may need to weld a heavy-duty lifting eye or a threaded stud directly onto the top of the seized exhaust valve body.
• Hydraulic Jacking: Set up a bridge over the cylinder head and use a high-capacity hydraulic jack (10–30 tons) pulling on the welded stud. Apply steady pressure while tapping the valve body to encourage movement.

4. Destructive Removal (Last Resort)

If the valve remains seized after hydraulic and thermal attempts:

• Drilling/Milling: Use a portable magnetic drill to drill out the valve body's core or mill away the seating flange to relieve the compression.
• Gouging: Carefully use an oxy-acetylene torch or carbon-arc gouging to cut a vertical slit inside the valve body. Caution: Extreme care must be taken not to damage the cylinder head bore.
• Collapsing: Once a slit is cut, use a heavy drift and hammer to collapse the valve body inward, breaking its grip on the head.

5. Post-Removal Inspection and Repair

• Cylinder Head Bore: Inspect the head bore for scoring or cracks. Use emery cloth or a hone to clean the landing surface.
• Thread Restoration: Since the valve body is being replaced, the damaged threads are a non-issue for the old part. However, ensure the exhaust bellows and studs on the cylinder head are inspected for collateral damage.
• Pressure Test: After fitting the new valve assembly, perform a cooling water pressure test to ensure the seals are watertight.

• Tie rods may not be tightened to the manufacturer's specifications during assembly or maintenance, leading to slackness over time.
• Prolonged operation under overload conditions can cause increased stress on the tie rods, potentially loosening them.
• Loose foundation bolts can lead to excessive vibration, which can shake the tie rods loose.
• Loose pinching screws on the tie rods themselves can allow them to vibrate and loosen.
• A severe scavenge fire can generate intense heat, causing the tie rods to expand. This thermal expansion can eventually loosen the tie rods.
• Tie rods, like any metal component, can experience elongation over time due to ageing and fatigue. This elongation can contribute to slackness.
• Rapid changes in engine load due to heavy weather conditions can contribute to tie rod slackening.

• Slack tie rods result in uneven loading of the engine on the transverse girder, leading to crankshaft misalignment. This misalignment can damage bearings and cause uneven wear on other engine components.
• The relative movement between the engine structure caused by slack tie rods leads to fretting, a type of surface wear that occurs due to microscopic vibrations.
• Fretting can cause accelerated wear on the crosshead guide, cylinder liner, and stuffing box due to misalignment.
• The overall alignment of the engine and running gear can be compromised, impacting performance and potentially leading to damage.
• Excessive vibration of the engine may lead to failure of the components, which may be even extended to failure of turbocharger bearings
• The vibrations can further loosen foundation bolts and chocks, exacerbating the problem.
• In severe cases, slack tie rods can lead to damage of the bedplate, frame, and entablature, requiring costly repairs.

To minimise the problem of tie rods becoming slack, it is essential to regularly check their tightness according to the maintenance schedule provided by the manufacturer. This includes following the manufacturer's specific tightening procedures and applying the correct hydraulic pressure to ensure even tightening of all tie rods. Preventing engine overloading is also important, as operating the engine under excessive loads for prolonged periods should be avoided to reduce the risk of tie rod slackness.

(a) Fatigue is the process leading to localized structural damage in materials subjected to cyclic loading.

• Fatigue failure can occur even when stress levels are below the ultimate tensile strength of the material.
• It primarily results from repetitive cyclic loads, causing microscopic crack formation and growth over time until the component fails.

Contributing factors include:

• High cyclic loading
• Vibrations
• Material or manufacturing defects
• Corrosion
• Improper handling and machinery operation

(b) Difference between high stress/low cycle and low stress/high cycle fatigue

High-cycle fatigue (low stress-high cycle):

• This occurs at lower stress levels over a high number of cycles, resulting in elastic deformation. The component can withstand more cycles at these lower stress levels, and its life expectancy is determined by the S-N curve, which predicts the number of cycles before failure at a given stress level. For example, fatigue in turbocharger blowers often results from prolonged vibration over numerous cycles.

Low-cycle fatigue (high stress-low cycle):

• This occurs at high-stress levels over fewer cycles, causing plastic deformation in the material. This type of fatigue is typically assessed by a strain curve. If the stress level increases, the component's operating life decreases, as higher stress accelerates the onset of failure. For example, air receivers filling automatically face high stress and experience fewer cycles before failure.

If stress levels or the number of cycles increase beyond the material’s capacity, failure will occur sooner. It is important to keep stress levels within allowable limits for extended component life.

• Defects in metal concentrate stress locally, raising stress levels in those areas and leading to early failure.

Types of Defects That Reduce Fatigue Strength:

• Surface roughness, porosity, inclusions, abrupt section changes, and manufacturing flaws act as stress risers.
• Residual stress due to coarse grain structure, improper chemical composition, and cold working.
• Environmental factors like corrosion and erosion.
• Faulty assembly or workmanship can introduce additional stress, decreasing component life.

Fuel Timing Faults:

• Pre-ignition creates excessive peak pressures, potentially causing cracks in bed plates, especially around bearing pockets.
• Delayed injection can lead to after-burning and scavenging fires, loosening tie bolts and causing fatigue cracks.

Cylinder Power Balance:

• Proper fuel injection timing and balanced cylinder power minimize vibration.
• Any imbalance in timing or power can increase vibration, transmitting stress to bed plates and causing fatigue cracks.

(a) Regular internal inspection of air bottle:

• The bottles should be inspected every year and the mountings to be overhauled every two years.
• The reservoirs should be carefully examined for corrosion and pitting.
• Corrosion and pitting usually occur on the bottom of the reservoir, around the valve openings and in the way of any cooler areas.
• If the air reservoir is adjacent to the shipside, which is often cooler than the other parts of the engine room, corrosion or pitting can be expected on the inside cold surface of the reservoir adjacent to the shipside.
• The corrosion and pitting are associated with vapour coming out of suspension from the compressed air pumped into the reservoir.
• The moisture forms on the bottom and cold surfaces and causes corrosion.
• Oil particles may also be carried over with the compressed air from the compressor, and if oxidation of the oil occurs this may also lead to corrosion and pitting.
• A further internal examination is to be conducted for: pitting corrosion, fatigue cracking, laminations, indentations and localised bulging

(c) Parts to be inspected.

• The air bottle is fitted with stop, safety and drain valves and a manhole door at one end.
• Reservoirs are inspected regularly; precautions must be taken against internal corrosion and pitting, especially at the top and bottom end. (Bottom where condensate accumulates)
• It is of great importance that the reservoir should always be well-drained and that a protection coating should be applied.
• All valves should be thoroughly maintained, and inspection should be carried out on these valves for air tightness, corrosion, erosion, and soundness of valve spindle and springs (hammer test) should be inspected.
• Manhole door joint face, door studs and nuts, and radial clearance between door and frame (1/16" in diameter) must be checked for corrosion and erosion.

(d) Test for air bottle if cannot enter.

• Large pressure vessels, which can perform internal and external inspection, do not need to perform hydraulic pressure tests if the visual condition is good and no defect.
• If the pressure vessel cannot enter and cannot perform internal inspection must be hydraulically tested.
• The test pressure is 1.25 x working pressure and is maintained for 10 minutes.

How pressure test carried out.

• To pressure test the air bottle the hydraulic pressure is 1.25 x working pressure should be maintained for 10 minutes in accordance with the requirements of the classification societies concerned, during which the surveyor should carry out a thorough examination for any defects. A special pressure gauge known to be accurate is used when the receiver is undergoing the hydraulic test.
• The receiver will have to be sealed, wire brushed internally and thoroughly cleaned out in preparation for the test. Cleaning the unit internally must not be done by the use of toxic or inflammable agents.
• The valve chest will be removed and a plate having a screwed hole in the centre will be joined up. The receiver is filled with water until water shows at the air vent to ensure that no air is trapped inside.
• One end of the high-pressure flexible pipe will be screwed into the screwed hole of the plate and the other end of the pipe will be attached to the discharge side of the hydraulic hand pump. The hand pump will now be started and the pressure gradually brought up to the stated amount.

For a vessel approaching port after a long sea passage, it is essential to ensure that all deck hydraulic cranes, winches, and mooring machinery are in reliable working condition. Continuous exposure to salt spray, humidity, and long periods of inactivity can lead to corrosion, stiffness, or deterioration of hydraulic systems. Therefore, a systematic and well-planned maintenance routine must be carried out to avoid any failure during cargo handling or mooring operations.

1. General Preparation and Visual Inspection

The maintenance should begin with an overall inspection of the deck machinery and surrounding areas. All protective coverings such as canvas sheets, lashings, and weatherproof tapes must be removed from control panels, limit switches, and exposed components. The crane pedestals, winch foundations, and supporting structures should be carefully examined for signs of cracks, deformation, or excessive corrosion that may have developed during heavy weather conditions. It is also important to ensure that all working areas are free from loose items, obstructions, or stored materials that could interfere with safe operation.

2. Hydraulic System Maintenance

Since cranes and winches primarily depend on hydraulic power, the hydraulic system requires thorough attention. The oil level in the hydraulic reservoirs should be checked and topped up if necessary. The condition of the oil must also be assessed; a milky appearance may indicate water contamination, while foaming suggests air ingress. Filters should be inspected by checking differential pressure indicators, and clogged elements must be replaced to maintain proper flow. All pipelines, hoses, clamps, and connections should be examined for leakage, cracks, or bulging. Additionally, the cooling arrangement for the hydraulic oil—whether air-cooled or water-cooled—must be verified to ensure that overheating does not occur during continuous cargo operations.

3. Lubrication and Greasing

During long voyages, exposed moving parts may lose lubrication, leading to wear or seizure. Therefore, all lubrication points must be serviced using a grease gun. Bearings in crane slewing rings, sheaves, and winch drums should be properly greased. Open gears, such as those used in crane slewing mechanisms and winch drives, should be coated with suitable open gear lubricant. Wire ropes used for hoisting and luffing must be inspected for dryness, corrosion, or broken strands, and dressed with appropriate wire rope lubricant to maintain flexibility and reduce internal friction.

4. Brake and Clutch Checks

The braking system is critical for both cargo handling and mooring safety. Brake linings should be inspected for wear and checked to ensure they are free from oil or grease contamination. The effectiveness of brakes must be tested, confirming that spring-applied (fail-safe) brakes engage properly when hydraulic pressure is released and fully disengage when pressure is applied. Clutches should be operated to confirm smooth engagement and disengagement without sticking or slipping.

5. Electrical and Control System Checks

All electrical and control components must be tested to ensure safe operation. Limit switches for hoisting, lowering, and slewing should be physically tested to confirm proper functioning. Emergency stop buttons at local and remote stations must be checked to ensure immediate shutdown capability. Control levers or joysticks should move smoothly and return automatically to the neutral position, indicating correct spring action and control responsiveness.

6. Operational Trials (Dry Run)

Finally, a full operational trial should be conducted at least 24 hours before arrival. Each crane and winch should be run without load through its complete range of motions, including hoisting, luffing, and slewing, for a sufficient duration. This helps circulate hydraulic oil, remove stiffness, and bring the system to operating temperature. If any maintenance work has been carried out, the system should be properly bled to remove trapped air. Mooring winches, especially those fitted with auto-tensioning systems, should be tested to ensure they can maintain line tension effectively during berthing.

To obtain accurate and reliable crankshaft deflection readings, it is essential that certain ideal conditions are satisfied. These conditions ensure that the readings truly reflect the alignment of the crankshaft and are not influenced by external factors.

• Firstly, the ship should be afloat and on an even keel, meaning there should be no significant trim or list. If the vessel is inclined, hull distortion can affect the crankshaft alignment and lead to incorrect readings.
• Secondly, weather and sea conditions should be calm. Excessive rolling or pitching can disturb the dial gauge and introduce errors during measurement.
• The loading condition of the ship should be consistent with previous measurements (whether in ballast or loaded condition). This allows for meaningful comparison of readings over time, as hull deflection varies with loading.
• The engine temperature should be stable, preferably in a cold or ambient condition. This is important because temperature variations can cause thermal expansion of engine components, which will influence deflection values.
• Finally, the turning gear should be properly engaged to rotate the engine slowly. However, when taking the actual readings, care should be taken to ensure that no unnecessary load or backlash from the turning gear affects the measurements.

Accurate readings are achieved by following correct procedures and ensuring proper handling of measuring instruments.

• To begin with, the dial gauge must be properly calibrated and checked for smooth operation before use. Any fault in the instrument will directly affect the accuracy of the readings.
• The gauge should be positioned exactly between the designated center punch marks on the crank webs. This ensures that all measurements are taken at a consistent radius, which is essential for reliable comparison.
• Before starting, the dial gauge is set to zero at the bottom dead centre (BDC) position, usually just after passing the connecting rod. This serves as the reference point for all subsequent readings.
• The crankshaft should be rotated in one continuous direction, typically in the ahead direction. Reversing direction can introduce errors due to backlash in bearings or the turning gear.
• After completing a full 360-degree rotation, the reading should return to the initial zero (or very close to it). If there is a significant deviation, it indicates possible error in the measurement process, and the readings should be repeated.

Purpose

The main purpose of taking crankshaft deflection readings is to assess the alignment of the main bearings and the crankshaft. Over time, uneven wear of bearings or structural deformation of the ship’s hull can cause misalignment. This leads to bending (deflection) of the crankshaft during rotation.

Regular monitoring helps in early detection of abnormalities, thereby preventing serious issues such as crankshaft fatigue, web cracking, or bearing failure.

Interpretation of Readings

Deflection readings are used to evaluate both vertical and horizontal alignment of the crankshaft:

• Vertical Alignment is determined using the difference between the Top (T) and Bottom (B) readings.
  • A positive (+) value indicates that the crank webs are opening at the top. This usually suggests that the middle bearing is higher than adjacent bearings, or that the adjacent bearings have worn down.
  • A negative (–) value indicates that the webs are closing at the top, suggesting that the middle bearing is lower or excessively worn.
• Horizontal Alignment is assessed using Port (P) and Starboard (S) readings. These values indicate any side-to-side misalignment of the crankshaft.

Finally, all readings must be compared with the manufacturer’s specified allowable limits. If any value exceeds these limits, corrective actions such as bearing adjustment, replacement, or engine re-alignment (re-chocking) must be carried out to restore proper alignment.

Overhauling and Setting of Boiler Safety Valves

Boiler safety valves are critical protective devices designed to automatically release excess steam pressure and prevent boiler overpressure. Most auxiliary boilers are fitted with full-lift or pop-type double spring safety valves, which open rapidly and fully once the set pressure is reached, ensuring effective pressure relief.

A typical boiler safety valve consists of the following main components:

• Valve and Seat: Usually made of high-grade materials such as stainless steel or Monel metal to resist erosion (wire drawing) caused by high-velocity steam.
• Compression Springs: Helical springs that hold the valve tightly closed against steam pressure until the set pressure is reached.
• Valve Lip / Shroud (Waste Steam Piston): A specially designed projection that increases the effective area when the valve begins to lift, producing a rapid “pop” action and ensuring full opening.
• Spindle and Guides: Maintain alignment and ensure smooth vertical movement of the valve.
• Waste Steam Pipe: A large-diameter pipe that safely discharges steam to the atmosphere.
• Easing Gear: A mechanical arrangement that allows manual lifting of the valve for testing or emergency purposes.
• Drain Arrangement: Prevents accumulation of condensate in the valve body, which could otherwise affect operation.

1. Isolation and Removal: Isolate the boiler, ensure zero pressure, and remove the safety valve carefully from its seating.
2. Dismantling: Mark all parts for correct reassembly. Carefully dismantle the valve, including removal of springs, spindle, and valve disc.
3. Cleaning: Clean all components thoroughly to remove deposits, scale, and corrosion products.
4. Inspection of Components: Each component must be examined for wear, damage, or distortion (details given below).
5. Repair and Refurbishment: Carry out necessary repairs such as lapping of valve and seat, replacement of worn parts, or renewal of springs if required.
6. Reassembly: Reassemble the valve carefully, ensuring correct alignment and clearances. Avoid over-tightening or misalignment during assembly.

Parts Requiring Close Attention During Overhaul

• Valve and Seat Surfaces: These must be perfectly smooth and free from pitting, scale, or wire drawing. They should be lapped to a fine finish to ensure a steam-tight seal and prevent leakage or “simmering.”
• Springs: Check for cracks, corrosion, and loss of elasticity (permanent set). Defective springs will affect the lifting pressure and proper reseating of the valve.
• Spindle and Guides: Ensure the spindle is straight and moves freely. Guides should be clean and free from deposits, as any restriction may cause sticking or improper operation.
• Lip/Shroud Clearance: The clearance between the valve lip and seat ring is critical for correct “pop” action. Incorrect clearance may result in delayed opening or poor reseating.
• Drain Passage: Ensure that drain holes are clear. Blockage can allow condensate to accumulate, which may interfere with valve operation and cause corrosion.

After overhaul, safety valves must be reset and tested, usually in the presence of a classification society surveyor.

1. Preparation: Ensure that the boiler pressure gauge is calibrated and accurate. One safety valve is temporarily gagged (held closed) while the other is being set.
2. Raising Boiler Pressure: Gradually raise the boiler pressure up to the Maximum Allowable Working Pressure (MAWP).
3. Adjustment of Set Pressure: Adjust the compression of the spring using the adjusting nut until the valve lifts (“pops”) at the required pressure.
   • For boilers with two valves, typically one is set at the working pressure and the other slightly higher (e.g., about 3% above), as per class or manufacturer requirements.
4. Verification of Operation: Allow the valve to lift and reseat several times to confirm consistent operation. Check the blowdown, which is the difference between opening and closing pressure, typically around 3–5% of the set pressure.
5. Accumulation Test (if required): With the main steam stop valve closed and boiler firing at full capacity, verify that the pressure does not rise more than 10% above MAWP, ensuring adequate relieving capacity.
6. Sealing and Locking: Once the correct setting is confirmed, fit locking arrangements such as split collars or distance pieces. Apply a lead seal to prevent unauthorized adjustment.

(a) Severe engine vibration within a specific speed range can be caused by either internal or external factors.

Auxiliary Engine Big-End Bearing

A thorough inspection of all parts is essential before reassembly to ensure reliability and prevent premature failure.

1. Bearing Shells (Thin-walled):

• Visual Inspection: Examine the white metal surface for signs of wiping, pitting, or scuffing. Also check for fatigue cracks or cavitation damage, which indicate deterioration of the bearing surface.
• Back of the Shell: Inspect for fretting marks (black spots). These indicate that the shell has been moving inside the housing, usually due to loss of proper “crush.”
• Thickness Measurement: Measure the shell thickness at several locations using a ball-ended micrometer. Compare the readings with manufacturer limits to assess wear.

2. Crank Pin:

• Ovality and Taper: Measure the diameter at multiple positions (both vertical and horizontal planes) using an outside micrometer. Compare readings to detect ovality or taper.
• Surface Condition: Check for scoring, ridges, or heat discoloration (blue spots), which suggest overheating or lubrication failure.
• Oil Hole Condition: Ensure the oil hole is clean and free from obstruction. The edges should be smooth and properly radiused to avoid stress concentration.

3. Serrations (Joining Faces):

• Condition of Mating Surfaces: Inspect the serrated faces between the connecting rod and bearing cap for fretting or crushing.
• Cleanliness: These surfaces must be perfectly clean. Even small particles can cause misalignment, leading to uneven loading and bearing failure.

4. Connecting Rod Bolts:

• Crack Detection: Inspect bolts carefully, especially at thread roots and the transition between shank and head, using methods such as Liquid Penetrant Testing (LPT).
• Elongation Check: Measure the bolt length and compare it with the original unstretched length. If permanent elongation exceeds permissible limits, the bolt must be replaced.

After satisfactory inspection, the bearing is assembled as follows:

1. Preparation: Clean the bearing housing and the back of the shells thoroughly. Wipe the crank pin with a lint-free cloth and apply a light coat of clean lubricating oil.
2. Fitting of Shells: Place the bearing shells correctly into the connecting rod and cap, ensuring the locating lugs fit properly into their recesses.
3. Mounting on Crank Pin: Position the connecting rod onto the crank pin (or bring the pin into position). Fit the bearing cap, ensuring that the match marks on the rod and cap align correctly.
4. Tightening of Bolts:
   • Clean and lightly lubricate the bolt threads and seating surfaces.
   • Tighten the bolts in stages (for example, 30% → 60% → 100%) using a hydraulic jack or torque wrench as specified.
   • If the angle-of-turn method is used, ensure reference marks are correctly aligned during tightening.

Once assembly is complete, several checks must be carried out before the engine is put into operation:

1. Bearing Clearance (Oil Clearance): Measure the clearance using long feeler gauges inserted between the crank pin and bearing shell at the point of maximum gap (top or bottom). Ensure it is within specified limits (typically around 0.15–0.25 mm).
2. Side Clearance (Axial Float): Check the clearance between the connecting rod and crank web. This ensures there is sufficient space for free movement and thermal expansion without binding.
3. Swing Test: If the piston is disconnected, the connecting rod should swing freely under its own weight (in smaller engines) or move easily by hand, confirming correct alignment and clearance.
4. Turning Gear Test: Engage the turning gear and rotate the engine through at least two full revolutions. Observe for smooth movement, absence of hard spots, and listen for any abnormal metallic sounds.
5. Lubrication Check: Start the pre-lubrication pump and inspect the bearing area. Oil should be seen flowing or weeping from the edges of the bearing, confirming proper lubrication supply.
6. Securing Arrangements: Ensure all locking devices such as tab washers, locking wires, or pins are properly fitted to prevent loosening of bolts during operation.

Engine Room Overhead Crane: Maintenance and Operational Procedure

To the Chief Engineer, I propose the following procedure to ensure the engine room overhead crane is maintained and operated correctly, focusing on safety, compliance, and longevity.

Proposed Procedure for Crane Maintenance and Operation

1. Daily Pre-Use Checks:

• The duty engineer must perform a visual inspection before each use. This involves checking the wire rope condition (for kinks, corrosion, or broken strands), the hook integrity (for deformation or wear), the functionality of the brakes, and the correct operation of the limit switches. Any defects or abnormalities must be logged and reported to the Chief Engineer immediately, rendering the crane out of service until repaired.

2. Planned Maintenance System (PMS) Integration:

The crane must be fully integrated into the vessel’s Planned Maintenance System (PMS). Scheduled tasks should include:

• Regular lubrication of moving parts (bearings, sheaves).
• Electrical inspections of the motor, wiring, and control panel.
• Periodic testing of the load brake and hoist mechanism.
• Wire rope replacement based on manufacturer's specified running hours or condition.

3. Operational Training and Authorization:

Strict control over operation is essential. Only authorized personnel who have successfully completed formal operational training should use the crane. Training must cover:

• Proper use of the control system and pendant.
• Understanding and adherence to the crane's Safe Working Load (SWL).
• Safe rigging and signalling procedures.
• Emergency stop procedures.

4. Load Testing and Certification:

The crane's integrity must be periodically verified. A mandatory load test must be performed at intervals not exceeding 5 years, or after any major repair or modification, in accordance with flag state regulations.

Required Tests and Certificates

The following certifications are required to demonstrate the crane's fitness for service and compliance with international maritime standards:

Issuing Authority

The required certificates must be issued by a competent authority recognized by the vessel's Flag State Administration. This is typically:

• A Class-approved service provider.
• A Recognized Organization (RO) (e.g., Lloyd’s Register, DNV, ABS, RINA, NK, Bureau Veritas) authorized to conduct surveys on behalf of the Flag State.

All records and certificates must be properly filed and kept ready for inspection by authorities and auditors.

Survey of Oil-Lubricated Stern Bearing and Shaft

(a) Survey Procedure

The survey of an oil-lubricated stern tube shaft (tailshaft) is normally carried out at five-year intervals, although extensions may be granted when supported by satisfactory condition monitoring. The objective of the survey is to assess wear, detect defects, and ensure the continued reliability of the shafting system.

1. Wear-Down Measurement

Before any dismantling work begins, the vertical wear-down (clearance) of the stern bearing is measured using a poker gauge.

• This measurement indicates the extent of bearing wear.
• The obtained value is compared with:
  • Original (as-built) clearances
  • Previous survey readings
• This comparison helps in determining the wear rate and whether it is within acceptable limits.

2. Oil Sample Analysis

Samples of stern tube lubricating oil are periodically analyzed to assess internal condition without dismantling. The analysis includes checking for:

• Water contamination
• Metallic particles such as iron, copper, and white metal
• Changes in viscosity and acid number

Consistently satisfactory results indicate good internal condition and may support extension of the survey interval.

3. Visual Inspection of the Shaft

Once the shaft is withdrawn (or exposed during a partial survey), a detailed visual examination is carried out.

• The shaft surface is checked for:
  • Corrosion
  • Pitting
  • Scoring or surface damage
• Special attention is given to areas in contact with seals, as these are more prone to wear and damage.

4. Non-Destructive Testing (NDT)

Critical regions of the shaft are subjected to NDT methods such as:

• Magnetic Particle Inspection (MPI)
• Dye Penetrant Testing (DPT)

These tests are focused on:

• The tapered end
• Keyway
• Threaded portions

The purpose is to detect fatigue cracks or hidden defects that may not be visible to the naked eye.

5. Bearing Inspection

The stern bearing, usually lined with white metal, is carefully examined for:

• Wiping (indicative of overheating or lubrication failure)
• Pitting
• Fatigue cracking

In addition, the bond between the white metal lining and the backing shell is checked to ensure structural integrity.

6. Seal Examination

The sealing arrangement, typically consisting of rubber lip seals, is inspected for:

• Wear and tear
• Loss of elasticity
• Hardening or cracking

Even if no obvious defects are visible, these seals are generally renewed during major surveys to ensure reliability.

(b) Proving Integrity of Outboard Seal Before Dock Flooding

The outboard seal is the final barrier that prevents:

• Oil leakage from the stern tube into the sea
• Seawater ingress into the stern tube

Therefore, its integrity must be confirmed before the dry dock is flooded.

Methods of Testing

1. Static Pressure Test

This is the most commonly used method.

• The stern tube is completely filled with oil.
• The header tank level is raised to create a pressure head slightly higher than the expected draft pressure when the vessel is afloat.
• The aft seal area (near the rope guard) is observed over a period (typically 6–12 hours).
• Any oil seepage indicates leakage, while no leakage confirms proper sealing.

2. Air Pressure Test

• Low-pressure compressed air is introduced into the space between the sealing rings.
• The pressure is monitored using a pressure gauge over a specified duration.
• If the pressure remains constant, the seal is considered:
  • Airtight
  • Therefore, effectively watertight

  3. Vacuum Test

  • A vacuum is applied to the seal arrangement.
  • Stability of the vacuum over time indicates that:
    • The seal lips are maintaining proper contact with the shaft liner
    • No leakage paths are present

    4. Interspace Drain Check

    • In systems with an interspace (void) between seals, the drain from this space is opened during testing.
    • Observation of oil or air escaping from this drain indicates:
      • Leakage past one or more sealing rings
      • Failure of seal integrity

• Visual inspection: The crack surface will have a smooth, polished finish, while the remaining material will show a granular texture.
• Crack pattern: The fatigue crack surface will display a series of curved visible lines, which are a result of the cyclical loading and stress.
• Non-Destructive Testing (NDT): Techniques such as Dye-Penetrant Testing or Magnetic Particle Testing are commonly used to identify cracks in the material.

Stage I: Initial Crack Initiation:

• The first crack forms at a point of high stress, usually around sharp corners, notches, or surface defects. This is the stage where microscopic cracks begin to form due to repeated loading.

Stage II: Progressive Crack Growth:

• The initial crack propagates slowly under cyclic loading. This stage is characterized by relatively slow, stable crack growth. The crack propagates most rapidly in a direction perpendicular to the main tensile stress.

Stage III: Final Fracture:

• Once the crack has grown to a certain size, the remaining material can no longer withstand the applied stress. The crack grows rapidly, leading to a catastrophic failure of the component. This is the final stage of fatigue failure, often happening suddenly.

• The crankshaft should be made from a material with high fatigue strength, as opposed to high ultimate tensile strength (UTS). Materials with higher fatigue strength are better able to resist the initiation of cracks.
• Forging the crankpin and webs from a single piece of material ensures a continuous grain flow, enhancing strength and reducing stress concentrations. The forging process itself also helps to consolidate material, reducing the number of internal defects.
• Cold rolling fillets (radii) at stress concentration points reduces stress concentration by removing sharp corners and inducing compressive residual stresses. This smoothing improves the fatigue resistance.
• Shot Peening/Laser Peening treatments introduce compressive residual stresses near the surface, thereby offsetting the tensile stresses during operation and making crack initiation more difficult. Laser peening imparts a deeper compressive layer compared to shot peening.
• Increased web thickness improves the component's ability to accommodate tensile stresses, reducing the likelihood of fatigue crack initiation.
• The High-Frequency Mechanical Impact Treatment (HFMIT) method is particularly effective for welded surfaces, improving their fatigue resistance.

• Solenoid valve
• Thermostatic expansion valve (TEV)
• Evaporator coil
• Thermostat

For example:

• Meat Room: -16°C to -11°C
• Vegetable Room: +5°C

When the temperature in a room rises above its set point, the thermostat senses the change and opens the solenoid valve. This allows refrigerant to flow to the evaporator via the TEV, cooling the room. Once the room's desired temperature is achieved, the thermostat shuts the solenoid valve, stopping refrigerant flow.

The compressor operates based on the overall demand across all rooms. It will run when at least one solenoid valve is open and cut off when all are closed, reducing suction pressure.

• The thermostat detects an increase in room temperature and energizes the solenoid valve for that specific room.
• The solenoid valve opens, allowing refrigerant to flow to the evaporator via the TEV, which reduces the refrigerant's pressure and temperature.
• The refrigerant absorbs heat from the room, evaporating as it passes through the evaporator coil.
• As refrigerant vapor returns to the compressor, suction pressure increases.
• The LP cut-out resets, and the compressor starts, compressing the refrigerant into a high-pressure, high-temperature gas.
• The refrigerant is condensed back to a liquid and recirculated. The cycle continues until the desired temperature is achieved, at which point the thermostat closes the solenoid valve.

Back pressure valves are installed in higher-temperature rooms (e.g., vegetable room) to prioritize refrigerant flow to colder rooms during heavy cooling demands.

High Pressure (HP) Cut-out:

• Trips the compressor when discharge pressure exceeds safe limits, protecting the system from overpressure.
• A manual reset is required.

Oil Differential Pressure Cut-out:

• Cuts off the compressor if oil pressure drops below the safe differential.
• Prevents damage due to inadequate lubrication.

Low Pressure (LP) Cut-out:

• Stops the compressor if suction pressure falls too low, preventing operation under low refrigerant conditions.
• Automatic reset.

Condenser Relief Valve:

• Relieves pressure from the condenser to prevent rupture or damage.

Safety Head:

• Lifts if liquid refrigerant enters the compressor to prevent mechanical damage.

Oil Heater:

• Prevents crankcase oil from becoming excessively cold and losing viscosity.

• Monitor running parameters daily.
• Perform maintenance as per the manufacturer’s guidelines.
• Test HP, LP, and oil differential cut-outs at regular intervals.
• Clean condenser coils and renew silica gel periodically.
• Check for correct oil levels.
• Conduct frequent checks to identify and rectify refrigerant leaks.
• Ensure proper defrosting of ice buildup on evaporator coils to maintain efficiency.
• Overhaul major components as recommended by the manufacturer to ensure reliability.
• Maintain proper logs and follow standard operating procedures for refrigeration system operation.

PREPARING AN F.O. STORAGE TANK FOR INTERNAL EXAMINATION (SURVEY)

Keeping safety of personnel paramount, the tank is gas-freed and made safe before entry under the requirements of the code of safe working practices and MARPOL (for oil residue) and the company's enclosed-space entry procedure.

Procedure

1. Pre-job planning and risk assessment: Identify the tank, inform the watch/ duty engineer, prepare a written risk assessment and a permit-to-work / enclosed space entry permit; brief all personnel, appoint a responsible officer in charge and a competent entry team/ stand-by watch.
2. Check tank contents and position: Confirm which F.O. storage tank, its capacity, contents (heavy fuel oil/ intermediate), and plan the transfer.
3. Empty the tank: Transfer the fuel out to another storage tank or settling tank using the transfer pumps, working through the sounding/ vent. Take care not to overfill the receiving tank; monitor soundings. Do not discharge any oil overboard (MARPOL reg 12); arrange for any sludge/ residue to be kept in a slop/ oily water system or to a reception facility.
4. Isolate the tank: Close and secure the suction valve (from the tank to the service system) and any filling/overflow/ vent valves connecting to the bunker system; lock off or blank them, and tag the valves with "isolated for tank entry".
5. Clean the tank: Drain as much as possible. Then, using appropriate means, remove sludge and residue; where possible, wash with hot fresh water (or use an approved tank-washing/ cleaning arrangement to a slop tank), and heat the tank (by steam coils/ heating) to lower viscosity and aid stripping. Remove deposits and scale. Where required, use the tank stripping/ evacuation means to a slop tank; never discharge residue overboard.
6. Gas-free (ventilate) and test the atmosphere: Connect the tank ventilation/ opening; ventilate thoroughly (mechanical ventilation/ natural) until the monitored atmosphere is safe. Before entry, test the tank atmosphere using an approved gas detector for: oxygen (O2 20.9% normal, min 19.5%); flammability (lower explosive limit - below 1% of LFL, i.e. essentially no flammable vapour); and toxic gases (hydrogen sulphide, carbon monoxide, hydrocarbon vapour). Re-test at set intervals.
7. Enclosed-space entry permit: Complete and sign the enclosed space entry permit; maintain a competent watch outside at all times, with a means of communication; provide for rescue/ emergency arrangements and a first-aid/ rescue plan; use a lifeline/ harness and a personal monitor where required.
8. Perform the internal examination: The surveyor/ attending engineer enters to carry out the internal examination - visual inspection of internals (stiffeners, tank top/ bottom, bulkheads, suction, coils, condition of coatings), thickness measurement (UTM) where required, and check for corrosion, pitting, cracks, and condition of the tank. Take representative test readings/ samples as required. Only personnel certified/ trained for enclosed space entry enter; obey time limits and continuous monitoring.
9. Withdraw and re-commission: When complete, all personnel exit, the manhole is closed and re-secured, the tank is re-vented/ purged as required for fuel service, and the suction/ vents are un-isolated and the tank re-pressurised/ refilled; carry out a leak/ stand test where needed.
10. Record: Complete the entry log, permit closure, and the survey record; retain findings for the classification report.

Starting Air Line System – Explosion in a 2-Stroke Engine

An explosion in the starting air line occurs when three essential elements are present together: fuel (oil), air (oxygen), and an աղբ ignition source. The main causes are:

• Accumulation of Lubricating Oil: Excess lubrication from the air compressor or oil carry-over due to faulty separators and filters can deposit oil inside the starting air manifold and pipelines.
• Leaking Starting Air Valves: If a starting air valve does not seat properly or remains slightly open, high-temperature combustion gases (above 1000°C) can flow back into the starting air line.
• Carbon Deposits: High compressor discharge temperatures may carbonize lubricating oil, forming deposits inside the pipeline. These deposits can glow or act as a combustible material.
• Formation of Oil Mist: When hot combustion gases come in contact with the oil film inside the pipe, the oil may vaporize into a fine, highly flammable mist.
• Adiabatic Compression (“Diesel Effect”): Sudden opening of valves can create pressure waves, causing localized temperature rise sufficient to ignite oil vapours present in the line.

Early detection of warning signs is critical to prevent serious damage. The following indications may be observed:

• High Temperature of Branch Pipes: A branch pipe that feels unusually hot during normal operation usually indicates leakage through a starting air valve.
• Discoloration of Paint: Burnt or blistered paint on branch pipes or the main manifold suggests overheating due to hot gas leakage.
• Pulsating Air Pressure: Fluctuations or “kicking” of the starting air pressure gauge while the engine is running may indicate backflow of gases.
• Abnormal Noise: Hissing sounds near the starting air valve during engine operation can point to leakage.
• High Compressor Discharge Temperature: Elevated temperatures at the compressor or after-cooler may indicate oil carry-over into the air system.
• Oil in Drain Lines: Excessive oil or oil-water emulsion observed during draining of air receivers or manifolds indicates contamination of the air system.

Immediate Actions (if leakage is suspected):

1. Isolate the Starting Air System: Close the main starting air valve and release pressure from the manifold.
2. Isolate the Affected Cylinder: Cut off fuel supply to the concerned cylinder if the leakage is significant, to reduce temperature and pressure.
3. Cooling Measures: Improve ventilation around the area, but avoid applying water directly on hot components to prevent thermal shock.

Operational Precautions:

• Regular Draining: Drain air receivers and starting air manifolds frequently (at least once per watch) to remove oil and moisture.
• Routine Temperature Checks (“Feel Test”): Physically check branch pipe temperatures after the engine reaches normal operating conditions to detect leaking valves early.
• Safety Devices: Ensure flame traps, bursting discs, or relief devices are in proper working condition and have not been tampered with.

Maintenance Requirements:

• Starting Air Valves: Periodically overhaul valves, lap the seating surfaces, and ensure a proper gas-tight seal. Test for leakage using soap solution or by checking for backflow.
• Air Compressors: Maintain piston rings, valves, and separators to prevent oil carry-over. Ensure after-coolers are clean and functioning efficiently.
• Non-Return Valves (NRV): Regularly inspect and overhaul NRVs to ensure they effectively prevent reverse flow of hot gases into the air system.
• Internal Cleaning of Manifold: Periodically clean and degrease the inside of the starting air manifold to remove accumulated oil deposits.

Inspection carried out during hull inspection:

(i) Shell Plating

• Common issues with shell plating include corrosion, dents, distortion, bulging, and cracks. Holes or welding defects can also be observed, particularly around deck equipment openings. Corrosion is usually more severe in areas with inadequate protective coatings.

Repairs:

• To address these defects, the shell plating must be cleaned thoroughly, and any corrosion removed before applying a fresh coat of protective paint. Dented or distorted plates can be straightened, and any cracks or holes should be welded. If the damage is extensive, sections of the plating may need to be replaced.

(ii) Fore End of Ship

• Similar to shell plating defects, but specifically focusing on deformation at the bow.
• Corrosion of the bow plating, floors, beams, and stringers due to exposure to seawater and environmental factors.
• Collisions or grounding events causing impact damage to Bow, Plate, Floor, Beams, Stringers, etc
• Defects in welds connecting structural components at the bow.
• Damage to the flared portion of the bow caused by falling of Anchor.

Repairs:

• Damaged components are repaired through welding, followed by cleaning and repainting to restore protection against corrosion. Severely compromised parts may require replacement.

(iii) Openings in Shell Plating

• Openings such as sea chests or overboard discharges may suffer from weld cracks, corrosion, or marine growth. Anodes installed near openings might be worn out or detached.

Repairs:

• Repairs include cleaning and welding damaged areas, renewing sacrificial anodes, and applying protective coatings to prevent future corrosion.

(iv) Rudder

• The rudder can develop cracks or dents in its side or top plates, leading to water ingress. Pintles may experience fractures, corrosion, or wear of sleeved bushes. Damage to threads, loss of securing nuts, or twisting of the rudder stock may also occur. Corrosion, paint fouling, or surface roughness on the rudder plates are common concerns.

Repairs:

• Cracks and dents are repaired through welding, while worn pintles or bushings are replaced. Corroded areas are cleaned and repainted to restore protective coatings. Twisting or bending of the rudder stock may require realignment or replacement if severe.

(v) Propeller and Stern Tube

• The propeller may show distortion, cracks, or loss of blade sections. The propeller cone and coupling bolts may sustain damage, while the stern tube may have worn or damaged seals, liners, or bearings.

Repairs:

• Minor surface defects on the shaft are machined out if the reduction in diameter is less than 3%. Cracks exceeding 15% of the shaft diameter necessitate replacement. Propeller blades are straightened by uniform heating and slow cooling, and minor cracks are repaired by flaring or welding. Damaged seals, liners, bearings, and coupling bolts are replaced, and proper shaft alignment is ensured. Heavily damaged propeller blades may be replaced entirely.

Overhauling and Setting of Boiler Safety Valves

Boiler safety valves are critical protective devices designed to automatically release excess steam pressure and prevent boiler overpressure. Most auxiliary boilers are fitted with full-lift or pop-type double spring safety valves, which open rapidly and fully once the set pressure is reached, ensuring effective pressure relief.

A typical boiler safety valve consists of the following main components:

• Valve and Seat: Usually made of high-grade materials such as stainless steel or Monel metal to resist erosion (wire drawing) caused by high-velocity steam.
• Compression Springs: Helical springs that hold the valve tightly closed against steam pressure until the set pressure is reached.
• Valve Lip / Shroud (Waste Steam Piston): A specially designed projection that increases the effective area when the valve begins to lift, producing a rapid “pop” action and ensuring full opening.
• Spindle and Guides: Maintain alignment and ensure smooth vertical movement of the valve.
• Waste Steam Pipe: A large-diameter pipe that safely discharges steam to the atmosphere.
• Easing Gear: A mechanical arrangement that allows manual lifting of the valve for testing or emergency purposes.
• Drain Arrangement: Prevents accumulation of condensate in the valve body, which could otherwise affect operation.

1. Isolation and Removal: Isolate the boiler, ensure zero pressure, and remove the safety valve carefully from its seating.
2. Dismantling: Mark all parts for correct reassembly. Carefully dismantle the valve, including removal of springs, spindle, and valve disc.
3. Cleaning: Clean all components thoroughly to remove deposits, scale, and corrosion products.
4. Inspection of Components: Each component must be examined for wear, damage, or distortion (details given below).
5. Repair and Refurbishment: Carry out necessary repairs such as lapping of valve and seat, replacement of worn parts, or renewal of springs if required.
6. Reassembly: Reassemble the valve carefully, ensuring correct alignment and clearances. Avoid over-tightening or misalignment during assembly.

Parts Requiring Close Attention During Overhaul

• Valve and Seat Surfaces: These must be perfectly smooth and free from pitting, scale, or wire drawing. They should be lapped to a fine finish to ensure a steam-tight seal and prevent leakage or “simmering.”
• Springs: Check for cracks, corrosion, and loss of elasticity (permanent set). Defective springs will affect the lifting pressure and proper reseating of the valve.
• Spindle and Guides: Ensure the spindle is straight and moves freely. Guides should be clean and free from deposits, as any restriction may cause sticking or improper operation.
• Lip/Shroud Clearance: The clearance between the valve lip and seat ring is critical for correct “pop” action. Incorrect clearance may result in delayed opening or poor reseating.
• Drain Passage: Ensure that drain holes are clear. Blockage can allow condensate to accumulate, which may interfere with valve operation and cause corrosion.

After overhaul, safety valves must be reset and tested, usually in the presence of a classification society surveyor.

1. Preparation: Ensure that the boiler pressure gauge is calibrated and accurate. One safety valve is temporarily gagged (held closed) while the other is being set.
2. Raising Boiler Pressure: Gradually raise the boiler pressure up to the Maximum Allowable Working Pressure (MAWP).
3. Adjustment of Set Pressure: Adjust the compression of the spring using the adjusting nut until the valve lifts (“pops”) at the required pressure.
   • For boilers with two valves, typically one is set at the working pressure and the other slightly higher (e.g., about 3% above), as per class or manufacturer requirements.
4. Verification of Operation: Allow the valve to lift and reseat several times to confirm consistent operation. Check the blowdown, which is the difference between opening and closing pressure, typically around 3–5% of the set pressure.
5. Accumulation Test (if required): With the main steam stop valve closed and boiler firing at full capacity, verify that the pressure does not rise more than 10% above MAWP, ensuring adequate relieving capacity.
6. Sealing and Locking: Once the correct setting is confirmed, fit locking arrangements such as split collars or distance pieces. Apply a lead seal to prevent unauthorized adjustment.

When an exhaust valve body is seized in the cylinder head and its internal threads for the bellows connection are damaged, the removal becomes a complex "over-limit" maintenance task. The following procedure combines mechanical extraction techniques with heat-based and structural solutions:

1. Preparation and Safety

• Isolate the Engine: Ensure the main engine is properly "blocked" (stopped, starting air isolated, turning gear engaged, and "Work in Progress" tags posted).
• Drain Cooling Water: Drain the cylinder head cooling water to avoid thermal shock or contamination during heating operations.
• Clear the Area: Remove the exhaust bellows (if possible) and all peripheral piping to provide maximum workspace.

2. Initial Extraction Attempts (Non-Destructive)

• Penetrating Oil: Apply high-quality penetrating oil or "freeze-off" spray to the seating area and let it soak for several hours.
• Thermal Expansion (Differential Heating):
  • Carefully apply heat (using a rosebud torch) to the cylinder head surrounding the valve body to expand the bore.
  • Simultaneously, apply cooling (CO2 or ice) to the valve body itself to shrink it.
• Impact Loading: Use a heavy-duty slide hammer or a pneumatic hammer with a flat bit to create vibrations that may break the rust/carbon bond.

3. Addressing Damaged Internal Threads

Since the internal threads for the bellows connection are stripped, standard lifting tools cannot be used.

• Fabricate a Custom Puller: Use a "stud-and-bridge" arrangement. If the threads are gone, you may need to weld a heavy-duty lifting eye or a threaded stud directly onto the top of the seized exhaust valve body.
• Hydraulic Jacking: Set up a bridge over the cylinder head and use a high-capacity hydraulic jack (10–30 tons) pulling on the welded stud. Apply steady pressure while tapping the valve body to encourage movement.

4. Destructive Removal (Last Resort)

If the valve remains seized after hydraulic and thermal attempts:

• Drilling/Milling: Use a portable magnetic drill to drill out the valve body's core or mill away the seating flange to relieve the compression.
• Gouging: Carefully use an oxy-acetylene torch or carbon-arc gouging to cut a vertical slit inside the valve body. Caution: Extreme care must be taken not to damage the cylinder head bore.
• Collapsing: Once a slit is cut, use a heavy drift and hammer to collapse the valve body inward, breaking its grip on the head.

5. Post-Removal Inspection and Repair

• Cylinder Head Bore: Inspect the head bore for scoring or cracks. Use emery cloth or a hone to clean the landing surface.
• Thread Restoration: Since the valve body is being replaced, the damaged threads are a non-issue for the old part. However, ensure the exhaust bellows and studs on the cylinder head are inspected for collateral damage.
• Pressure Test: After fitting the new valve assembly, perform a cooling water pressure test to ensure the seals are watertight.

• Tie rods may not be tightened to the manufacturer's specifications during assembly or maintenance, leading to slackness over time.
• Prolonged operation under overload conditions can cause increased stress on the tie rods, potentially loosening them.
• Loose foundation bolts can lead to excessive vibration, which can shake the tie rods loose.
• Loose pinching screws on the tie rods themselves can allow them to vibrate and loosen.
• A severe scavenge fire can generate intense heat, causing the tie rods to expand. This thermal expansion can eventually loosen the tie rods.
• Tie rods, like any metal component, can experience elongation over time due to ageing and fatigue. This elongation can contribute to slackness.
• Rapid changes in engine load due to heavy weather conditions can contribute to tie rod slackening.

• Slack tie rods result in uneven loading of the engine on the transverse girder, leading to crankshaft misalignment. This misalignment can damage bearings and cause uneven wear on other engine components.
• The relative movement between the engine structure caused by slack tie rods leads to fretting, a type of surface wear that occurs due to microscopic vibrations.
• Fretting can cause accelerated wear on the crosshead guide, cylinder liner, and stuffing box due to misalignment.
• The overall alignment of the engine and running gear can be compromised, impacting performance and potentially leading to damage.
• Excessive vibration of the engine may lead to failure of the components, which may be even extended to failure of turbocharger bearings
• The vibrations can further loosen foundation bolts and chocks, exacerbating the problem.
• In severe cases, slack tie rods can lead to damage of the bedplate, frame, and entablature, requiring costly repairs.

To minimise the problem of tie rods becoming slack, it is essential to regularly check their tightness according to the maintenance schedule provided by the manufacturer. This includes following the manufacturer's specific tightening procedures and applying the correct hydraulic pressure to ensure even tightening of all tie rods. Preventing engine overloading is also important, as operating the engine under excessive loads for prolonged periods should be avoided to reduce the risk of tie rod slackness.

(a) Fatigue is the process leading to localized structural damage in materials subjected to cyclic loading.

• Fatigue failure can occur even when stress levels are below the ultimate tensile strength of the material.
• It primarily results from repetitive cyclic loads, causing microscopic crack formation and growth over time until the component fails.

Contributing factors include:

• High cyclic loading
• Vibrations
• Material or manufacturing defects
• Corrosion
• Improper handling and machinery operation

(b) Difference between high stress/low cycle and low stress/high cycle fatigue

High-cycle fatigue (low stress-high cycle):

• This occurs at lower stress levels over a high number of cycles, resulting in elastic deformation. The component can withstand more cycles at these lower stress levels, and its life expectancy is determined by the S-N curve, which predicts the number of cycles before failure at a given stress level. For example, fatigue in turbocharger blowers often results from prolonged vibration over numerous cycles.

Low-cycle fatigue (high stress-low cycle):

• This occurs at high-stress levels over fewer cycles, causing plastic deformation in the material. This type of fatigue is typically assessed by a strain curve. If the stress level increases, the component's operating life decreases, as higher stress accelerates the onset of failure. For example, air receivers filling automatically face high stress and experience fewer cycles before failure.

If stress levels or the number of cycles increase beyond the material’s capacity, failure will occur sooner. It is important to keep stress levels within allowable limits for extended component life.

• Defects in metal concentrate stress locally, raising stress levels in those areas and leading to early failure.

Types of Defects That Reduce Fatigue Strength:

• Surface roughness, porosity, inclusions, abrupt section changes, and manufacturing flaws act as stress risers.
• Residual stress due to coarse grain structure, improper chemical composition, and cold working.
• Environmental factors like corrosion and erosion.
• Faulty assembly or workmanship can introduce additional stress, decreasing component life.

Fuel Timing Faults:

• Pre-ignition creates excessive peak pressures, potentially causing cracks in bed plates, especially around bearing pockets.
• Delayed injection can lead to after-burning and scavenging fires, loosening tie bolts and causing fatigue cracks.

Cylinder Power Balance:

• Proper fuel injection timing and balanced cylinder power minimize vibration.
• Any imbalance in timing or power can increase vibration, transmitting stress to bed plates and causing fatigue cracks.

(a) Regular internal inspection of air bottle:

• The bottles should be inspected every year and the mountings to be overhauled every two years.
• The reservoirs should be carefully examined for corrosion and pitting.
• Corrosion and pitting usually occur on the bottom of the reservoir, around the valve openings and in the way of any cooler areas.
• If the air reservoir is adjacent to the shipside, which is often cooler than the other parts of the engine room, corrosion or pitting can be expected on the inside cold surface of the reservoir adjacent to the shipside.
• The corrosion and pitting are associated with vapour coming out of suspension from the compressed air pumped into the reservoir.
• The moisture forms on the bottom and cold surfaces and causes corrosion.
• Oil particles may also be carried over with the compressed air from the compressor, and if oxidation of the oil occurs this may also lead to corrosion and pitting.
• A further internal examination is to be conducted for: pitting corrosion, fatigue cracking, laminations, indentations and localised bulging

(c) Parts to be inspected.

• The air bottle is fitted with stop, safety and drain valves and a manhole door at one end.
• Reservoirs are inspected regularly; precautions must be taken against internal corrosion and pitting, especially at the top and bottom end. (Bottom where condensate accumulates)
• It is of great importance that the reservoir should always be well-drained and that a protection coating should be applied.
• All valves should be thoroughly maintained, and inspection should be carried out on these valves for air tightness, corrosion, erosion, and soundness of valve spindle and springs (hammer test) should be inspected.
• Manhole door joint face, door studs and nuts, and radial clearance between door and frame (1/16" in diameter) must be checked for corrosion and erosion.

(d) Test for air bottle if cannot enter.

• Large pressure vessels, which can perform internal and external inspection, do not need to perform hydraulic pressure tests if the visual condition is good and no defect.
• If the pressure vessel cannot enter and cannot perform internal inspection must be hydraulically tested.
• The test pressure is 1.25 x working pressure and is maintained for 10 minutes.

How pressure test carried out.

• To pressure test the air bottle the hydraulic pressure is 1.25 x working pressure should be maintained for 10 minutes in accordance with the requirements of the classification societies concerned, during which the surveyor should carry out a thorough examination for any defects. A special pressure gauge known to be accurate is used when the receiver is undergoing the hydraulic test.
• The receiver will have to be sealed, wire brushed internally and thoroughly cleaned out in preparation for the test. Cleaning the unit internally must not be done by the use of toxic or inflammable agents.
• The valve chest will be removed and a plate having a screwed hole in the centre will be joined up. The receiver is filled with water until water shows at the air vent to ensure that no air is trapped inside.
• One end of the high-pressure flexible pipe will be screwed into the screwed hole of the plate and the other end of the pipe will be attached to the discharge side of the hydraulic hand pump. The hand pump will now be started and the pressure gradually brought up to the stated amount.

For a vessel approaching port after a long sea passage, it is essential to ensure that all deck hydraulic cranes, winches, and mooring machinery are in reliable working condition. Continuous exposure to salt spray, humidity, and long periods of inactivity can lead to corrosion, stiffness, or deterioration of hydraulic systems. Therefore, a systematic and well-planned maintenance routine must be carried out to avoid any failure during cargo handling or mooring operations.

1. General Preparation and Visual Inspection

The maintenance should begin with an overall inspection of the deck machinery and surrounding areas. All protective coverings such as canvas sheets, lashings, and weatherproof tapes must be removed from control panels, limit switches, and exposed components. The crane pedestals, winch foundations, and supporting structures should be carefully examined for signs of cracks, deformation, or excessive corrosion that may have developed during heavy weather conditions. It is also important to ensure that all working areas are free from loose items, obstructions, or stored materials that could interfere with safe operation.

2. Hydraulic System Maintenance

Since cranes and winches primarily depend on hydraulic power, the hydraulic system requires thorough attention. The oil level in the hydraulic reservoirs should be checked and topped up if necessary. The condition of the oil must also be assessed; a milky appearance may indicate water contamination, while foaming suggests air ingress. Filters should be inspected by checking differential pressure indicators, and clogged elements must be replaced to maintain proper flow. All pipelines, hoses, clamps, and connections should be examined for leakage, cracks, or bulging. Additionally, the cooling arrangement for the hydraulic oil—whether air-cooled or water-cooled—must be verified to ensure that overheating does not occur during continuous cargo operations.

3. Lubrication and Greasing

During long voyages, exposed moving parts may lose lubrication, leading to wear or seizure. Therefore, all lubrication points must be serviced using a grease gun. Bearings in crane slewing rings, sheaves, and winch drums should be properly greased. Open gears, such as those used in crane slewing mechanisms and winch drives, should be coated with suitable open gear lubricant. Wire ropes used for hoisting and luffing must be inspected for dryness, corrosion, or broken strands, and dressed with appropriate wire rope lubricant to maintain flexibility and reduce internal friction.

4. Brake and Clutch Checks

The braking system is critical for both cargo handling and mooring safety. Brake linings should be inspected for wear and checked to ensure they are free from oil or grease contamination. The effectiveness of brakes must be tested, confirming that spring-applied (fail-safe) brakes engage properly when hydraulic pressure is released and fully disengage when pressure is applied. Clutches should be operated to confirm smooth engagement and disengagement without sticking or slipping.

5. Electrical and Control System Checks

All electrical and control components must be tested to ensure safe operation. Limit switches for hoisting, lowering, and slewing should be physically tested to confirm proper functioning. Emergency stop buttons at local and remote stations must be checked to ensure immediate shutdown capability. Control levers or joysticks should move smoothly and return automatically to the neutral position, indicating correct spring action and control responsiveness.

6. Operational Trials (Dry Run)

Finally, a full operational trial should be conducted at least 24 hours before arrival. Each crane and winch should be run without load through its complete range of motions, including hoisting, luffing, and slewing, for a sufficient duration. This helps circulate hydraulic oil, remove stiffness, and bring the system to operating temperature. If any maintenance work has been carried out, the system should be properly bled to remove trapped air. Mooring winches, especially those fitted with auto-tensioning systems, should be tested to ensure they can maintain line tension effectively during berthing.

To obtain accurate and reliable crankshaft deflection readings, it is essential that certain ideal conditions are satisfied. These conditions ensure that the readings truly reflect the alignment of the crankshaft and are not influenced by external factors.

• Firstly, the ship should be afloat and on an even keel, meaning there should be no significant trim or list. If the vessel is inclined, hull distortion can affect the crankshaft alignment and lead to incorrect readings.
• Secondly, weather and sea conditions should be calm. Excessive rolling or pitching can disturb the dial gauge and introduce errors during measurement.
• The loading condition of the ship should be consistent with previous measurements (whether in ballast or loaded condition). This allows for meaningful comparison of readings over time, as hull deflection varies with loading.
• The engine temperature should be stable, preferably in a cold or ambient condition. This is important because temperature variations can cause thermal expansion of engine components, which will influence deflection values.
• Finally, the turning gear should be properly engaged to rotate the engine slowly. However, when taking the actual readings, care should be taken to ensure that no unnecessary load or backlash from the turning gear affects the measurements.

Accurate readings are achieved by following correct procedures and ensuring proper handling of measuring instruments.

• To begin with, the dial gauge must be properly calibrated and checked for smooth operation before use. Any fault in the instrument will directly affect the accuracy of the readings.
• The gauge should be positioned exactly between the designated center punch marks on the crank webs. This ensures that all measurements are taken at a consistent radius, which is essential for reliable comparison.
• Before starting, the dial gauge is set to zero at the bottom dead centre (BDC) position, usually just after passing the connecting rod. This serves as the reference point for all subsequent readings.
• The crankshaft should be rotated in one continuous direction, typically in the ahead direction. Reversing direction can introduce errors due to backlash in bearings or the turning gear.
• After completing a full 360-degree rotation, the reading should return to the initial zero (or very close to it). If there is a significant deviation, it indicates possible error in the measurement process, and the readings should be repeated.

Purpose

The main purpose of taking crankshaft deflection readings is to assess the alignment of the main bearings and the crankshaft. Over time, uneven wear of bearings or structural deformation of the ship’s hull can cause misalignment. This leads to bending (deflection) of the crankshaft during rotation.

Regular monitoring helps in early detection of abnormalities, thereby preventing serious issues such as crankshaft fatigue, web cracking, or bearing failure.

Interpretation of Readings

Deflection readings are used to evaluate both vertical and horizontal alignment of the crankshaft:

• Vertical Alignment is determined using the difference between the Top (T) and Bottom (B) readings.
  • A positive (+) value indicates that the crank webs are opening at the top. This usually suggests that the middle bearing is higher than adjacent bearings, or that the adjacent bearings have worn down.
  • A negative (–) value indicates that the webs are closing at the top, suggesting that the middle bearing is lower or excessively worn.
• Horizontal Alignment is assessed using Port (P) and Starboard (S) readings. These values indicate any side-to-side misalignment of the crankshaft.

Finally, all readings must be compared with the manufacturer’s specified allowable limits. If any value exceeds these limits, corrective actions such as bearing adjustment, replacement, or engine re-alignment (re-chocking) must be carried out to restore proper alignment.

Overhauling and Setting of Boiler Safety Valves

Boiler safety valves are critical protective devices designed to automatically release excess steam pressure and prevent boiler overpressure. Most auxiliary boilers are fitted with full-lift or pop-type double spring safety valves, which open rapidly and fully once the set pressure is reached, ensuring effective pressure relief.

A typical boiler safety valve consists of the following main components:

• Valve and Seat: Usually made of high-grade materials such as stainless steel or Monel metal to resist erosion (wire drawing) caused by high-velocity steam.
• Compression Springs: Helical springs that hold the valve tightly closed against steam pressure until the set pressure is reached.
• Valve Lip / Shroud (Waste Steam Piston): A specially designed projection that increases the effective area when the valve begins to lift, producing a rapid “pop” action and ensuring full opening.
• Spindle and Guides: Maintain alignment and ensure smooth vertical movement of the valve.
• Waste Steam Pipe: A large-diameter pipe that safely discharges steam to the atmosphere.
• Easing Gear: A mechanical arrangement that allows manual lifting of the valve for testing or emergency purposes.
• Drain Arrangement: Prevents accumulation of condensate in the valve body, which could otherwise affect operation.

1. Isolation and Removal: Isolate the boiler, ensure zero pressure, and remove the safety valve carefully from its seating.
2. Dismantling: Mark all parts for correct reassembly. Carefully dismantle the valve, including removal of springs, spindle, and valve disc.
3. Cleaning: Clean all components thoroughly to remove deposits, scale, and corrosion products.
4. Inspection of Components: Each component must be examined for wear, damage, or distortion (details given below).
5. Repair and Refurbishment: Carry out necessary repairs such as lapping of valve and seat, replacement of worn parts, or renewal of springs if required.
6. Reassembly: Reassemble the valve carefully, ensuring correct alignment and clearances. Avoid over-tightening or misalignment during assembly.

Parts Requiring Close Attention During Overhaul

• Valve and Seat Surfaces: These must be perfectly smooth and free from pitting, scale, or wire drawing. They should be lapped to a fine finish to ensure a steam-tight seal and prevent leakage or “simmering.”
• Springs: Check for cracks, corrosion, and loss of elasticity (permanent set). Defective springs will affect the lifting pressure and proper reseating of the valve.
• Spindle and Guides: Ensure the spindle is straight and moves freely. Guides should be clean and free from deposits, as any restriction may cause sticking or improper operation.
• Lip/Shroud Clearance: The clearance between the valve lip and seat ring is critical for correct “pop” action. Incorrect clearance may result in delayed opening or poor reseating.
• Drain Passage: Ensure that drain holes are clear. Blockage can allow condensate to accumulate, which may interfere with valve operation and cause corrosion.

After overhaul, safety valves must be reset and tested, usually in the presence of a classification society surveyor.

1. Preparation: Ensure that the boiler pressure gauge is calibrated and accurate. One safety valve is temporarily gagged (held closed) while the other is being set.
2. Raising Boiler Pressure: Gradually raise the boiler pressure up to the Maximum Allowable Working Pressure (MAWP).
3. Adjustment of Set Pressure: Adjust the compression of the spring using the adjusting nut until the valve lifts (“pops”) at the required pressure.
   • For boilers with two valves, typically one is set at the working pressure and the other slightly higher (e.g., about 3% above), as per class or manufacturer requirements.
4. Verification of Operation: Allow the valve to lift and reseat several times to confirm consistent operation. Check the blowdown, which is the difference between opening and closing pressure, typically around 3–5% of the set pressure.
5. Accumulation Test (if required): With the main steam stop valve closed and boiler firing at full capacity, verify that the pressure does not rise more than 10% above MAWP, ensuring adequate relieving capacity.
6. Sealing and Locking: Once the correct setting is confirmed, fit locking arrangements such as split collars or distance pieces. Apply a lead seal to prevent unauthorized adjustment.

Poor Performance of LT Cooler in a Centralized Cooling Water System – Rectification and Improvement Measures

If the Low Temperature (LT) cooler of the centralized cooling water system shows poor performance, a systematic and methodical approach should be followed to identify the cause and restore efficiency. The problem may be due to fouling, air binding, low flow, bypassing, or mechanical defects. The following measures should be initiated:

1. Immediate Operational Checks

Before opening the cooler, first determine whether the problem is due to a temporary operating condition or an actual defect.

• Compare the seawater inlet and outlet temperatures and the freshwater inlet and outlet temperatures with the design values given in the ship’s manual.
• A low temperature drop on the freshwater side indicates either:
  • poor heat transfer, or
  • insufficient water flow through the cooler.
  Part (b)

  Check for Air Venting

  • Inspect and vent the high-point air vents on the LT cooler freshwater side.
  • Air pockets trapped inside the cooler reduce the effective heat transfer area and lower cooling efficiency.
  Part (c)

  Check Pressures

  • Observe the pressure gauges on both the seawater side and freshwater side.
  • Low differential pressure may indicate:
    • pump malfunction, or
    • bypass valve stuck open.
  • High differential pressure may indicate:
    • fouling,
    • blockage due to marine growth on the seawater side, or
    • scale deposits on the freshwater side.

    2. Investigate Flow and Bypass Problems

    Part (a)

    Temperature Control Valve (TCV)

    • Check whether the automatic temperature control valve is operating correctly.
    • If the valve is stuck in a position that allows water to bypass the cooler, the cooling medium will not pass effectively through the cooler.
    • Verify actuator operation, control signal, and air supply pressure if pneumatically operated.
    Part (b)

    Seawater Strainer Inspection

    • Inspect the seawater inlet strainer, as clogging of the strainer is one of the most common causes of reduced seawater flow.
    • Clean and refit the strainer if fouled with mud, marine growth, or debris.
    Part (c)

    Check Valve Line-Up and Flow Balancing

    • Confirm that all valves in the LT cooling circuit are correctly lined up.
    • Ensure that no suction, discharge, or cooler isolation valve has been accidentally throttled or left partly closed.

    3. Rectification by Physical Inspection and Maintenance

    If the problem is not resolved by operational checks, the cooler should be isolated and inspected.

    Before carrying out maintenance, perform a risk assessment and follow Lock-Out/Tag-Out (LOTO) procedures.

    Part (a)

    Seawater Side Cleaning

    For a plate type LT cooler:

    • Drain the cooler and open the covers.
    • Inspect the plates for:
      • marine growth,
      • mud,
      • silt,
      • slime, or
      • other deposits.
    • Clean the plates using a soft brush and approved cleaning chemicals.
    • Do not use steel wire brushes, as they may damage the protective oxide layer of the stainless steel plates.
    Part (b)

    Freshwater Side Cleaning / Descaling

    • If scale formation is suspected on the freshwater side, carry out chemical cleaning / CIP (Cleaning in Place) using an approved mild descaling chemical suitable for plate heat exchangers.
    • Ensure the chemical used does not damage the plates or gaskets.
    Part (c)

    Plate Condition and Integrity Check

    • Inspect all plates for:
      • corrosion,
      • pitting,
      • erosion, and
      • physical damage.
    • Check for signs of inter-plate leakage or cross-contamination between seawater and freshwater.
    • If pinhole leakage is suspected, a dye penetrant test may be carried out.
    Part (d)

    Gasket Inspection

    • Check the condition of the plate gaskets for:
      • hardening,
      • cracking,
      • deformation, or
      • loss of elasticity.
    • If the cooler has been opened, it is good practice to replace or rejuvenate the gaskets before reassembly to prevent leakage.

    4. Long-Term Preventive Measures to Improve Performance

    Part (a)

    Maintain Correct Water Treatment

    • Ensure proper chemical treatment of the freshwater circuit using the recommended inhibitors such as nitrites / borates.
    • This helps prevent:
      • scaling,
      • corrosion, and
      • internal fouling.
      Part (b)

      Proper Sea Chest Management

      • In shallow, muddy, or silty waters, use the high sea chest where appropriate to reduce the entry of mud and silt into the seawater system.
      Part (c)

      Routine Back-Flushing and Strainer Maintenance

      • If fitted, ensure the automatic back-flushing system for seawater strainers is working properly.
      • Regular cleaning of strainers and seawater lines should be carried out to maintain good flow.
      Part (d)

      Maintain Performance Records

      • Keep a regular log of:
        • pressure drop across the cooler, and
        • temperature differential across the cooler.
      • This helps in identifying performance trends:
        • gradual deterioration usually indicates fouling,
        • sudden performance drop usually indicates obstruction, valve malfunction, or mechanical failure.

Auxiliary Engine Big-End Bearing

A thorough inspection of all parts is essential before reassembly to ensure reliability and prevent premature failure.

1. Bearing Shells (Thin-walled):

• Visual Inspection: Examine the white metal surface for signs of wiping, pitting, or scuffing. Also check for fatigue cracks or cavitation damage, which indicate deterioration of the bearing surface.
• Back of the Shell: Inspect for fretting marks (black spots). These indicate that the shell has been moving inside the housing, usually due to loss of proper “crush.”
• Thickness Measurement: Measure the shell thickness at several locations using a ball-ended micrometer. Compare the readings with manufacturer limits to assess wear.

2. Crank Pin:

• Ovality and Taper: Measure the diameter at multiple positions (both vertical and horizontal planes) using an outside micrometer. Compare readings to detect ovality or taper.
• Surface Condition: Check for scoring, ridges, or heat discoloration (blue spots), which suggest overheating or lubrication failure.
• Oil Hole Condition: Ensure the oil hole is clean and free from obstruction. The edges should be smooth and properly radiused to avoid stress concentration.

3. Serrations (Joining Faces):

• Condition of Mating Surfaces: Inspect the serrated faces between the connecting rod and bearing cap for fretting or crushing.
• Cleanliness: These surfaces must be perfectly clean. Even small particles can cause misalignment, leading to uneven loading and bearing failure.

4. Connecting Rod Bolts:

• Crack Detection: Inspect bolts carefully, especially at thread roots and the transition between shank and head, using methods such as Liquid Penetrant Testing (LPT).
• Elongation Check: Measure the bolt length and compare it with the original unstretched length. If permanent elongation exceeds permissible limits, the bolt must be replaced.

After satisfactory inspection, the bearing is assembled as follows:

1. Preparation: Clean the bearing housing and the back of the shells thoroughly. Wipe the crank pin with a lint-free cloth and apply a light coat of clean lubricating oil.
2. Fitting of Shells: Place the bearing shells correctly into the connecting rod and cap, ensuring the locating lugs fit properly into their recesses.
3. Mounting on Crank Pin: Position the connecting rod onto the crank pin (or bring the pin into position). Fit the bearing cap, ensuring that the match marks on the rod and cap align correctly.
4. Tightening of Bolts:
   • Clean and lightly lubricate the bolt threads and seating surfaces.
   • Tighten the bolts in stages (for example, 30% → 60% → 100%) using a hydraulic jack or torque wrench as specified.
   • If the angle-of-turn method is used, ensure reference marks are correctly aligned during tightening.

Once assembly is complete, several checks must be carried out before the engine is put into operation:

1. Bearing Clearance (Oil Clearance): Measure the clearance using long feeler gauges inserted between the crank pin and bearing shell at the point of maximum gap (top or bottom). Ensure it is within specified limits (typically around 0.15–0.25 mm).
2. Side Clearance (Axial Float): Check the clearance between the connecting rod and crank web. This ensures there is sufficient space for free movement and thermal expansion without binding.
3. Swing Test: If the piston is disconnected, the connecting rod should swing freely under its own weight (in smaller engines) or move easily by hand, confirming correct alignment and clearance.
4. Turning Gear Test: Engage the turning gear and rotate the engine through at least two full revolutions. Observe for smooth movement, absence of hard spots, and listen for any abnormal metallic sounds.
5. Lubrication Check: Start the pre-lubrication pump and inspect the bearing area. Oil should be seen flowing or weeping from the edges of the bearing, confirming proper lubrication supply.
6. Securing Arrangements: Ensure all locking devices such as tab washers, locking wires, or pins are properly fitted to prevent loosening of bolts during operation.

OVERHAUL OF AN OIL COOLED MAIN ENGINE PISTON AND ITS TESTING

Procedure for overhaul

1. Preparation: Stop the engine, secure turning gear, drain the piston cooling oil system, and arrange lifting gear/ the piston lifting rig. Obtain the maker's overhaul manual.
2. Remove the piston unit: Lift the cylinder cover; disconnect the piston rod from the crosshead (remove the piston rod clamp) and lift the piston (with rod) out of the liner. Land it on a stand/ blocks.
3. Dismantle the piston:

• Remove the piston crown (top) - un-torque the crown retaining bolts/screws as per maker (these may be a ring of bolts accessed from the top).
• Remove the piston rings from the ring grooves using a ring expander/ with care; number them and record their positions.
• Separate the crown from the skirt (shroud) - the crown and skirt are usually bolted (the crown-to-skirt joint bolts), with the crown being the upper, the skirt the lower part.
• Remove the internal piston pin (gudgeon pin) bush and withdraw the pin where the design allows; in others the pin is carried by the connecting rod.

1. Clean all components using an approved (caustic-free or appropriate) solvent; remove carbon from the crown and ring grooves with a scraper/ soft brush, avoiding burring the grooves.
2. Inspect each part:

• Crown: for cracking (particularly around the combustion bowl rim and valve recesses), burning, erosion, and the condition of the fire ring/flame ring on its underside.
• Ring grooves and lands: for wear, step/ ridge, and the condition of the top ring groove insert (let-in ring carrier/ chrome ring) if provided.
• Rings: for wear, broken/free rings, wear height and side/radial clearances; check gaps (end gap in bore, side clearance in groove).
• Skirt/ shroud: for scoring, scuffing, cracks and the condition of the lower oil scraper grooves.
• Pin, pin bush and boss bores: for wear, pitting and correct clearance; check the pin bush bore.
• Oil-return/ scavenge passages and the piston cooling oil galleries: must be clear; clean any sludge.

1. Renew as necessary: Replace rings (typically with oversize or standard new rings as per cylinder bore condition), renew the crown-to-skirt joint bolts/gaskets, renew the pin bush if worn, and renew the scraper rings. Use the OEM parts and tools.
2. Reassemble: Fit new rings with correct end gap staggering (180 deg or as maker); refit the crown onto the skirt, torque the crown bolts in the correct sequence and to the correct value; fit the pin seals; check the ring-groove and piston assembly clearances.
3. Final checks before refit: Check the piston pin float/ motion, the ring side clearances and that the rings are free in the grooves, and that the crown-to-skirt joint is uniform.

OEM tools used for overhauling the piston

• Piston lifting rig/ lifting sling (with the ceramic/ nylon and steel support cradle) to lift and carry the piston.
• Ring expander/ ring plier to remove and fit rings without breaking them.
• Torque wrench and correct sockets/ extension for the crown bolts (e.g. angle torquer/ tension wrench).
• Pin drift/pin puller and bush drift to remove the pin.
• Feeler gauges, micrometers and telescopic gauges for clearance measurement.
• Cleaning/ scraping tools (carbon scraper, groove cleaner) and torque/micro-check gauges
• Target/ tension wrench and the maker's lifting beam inserts.

Testing of the oil cooled piston after overhaul

1. Bar-check/ engine turning: Fit the piston and bar the engine over several revolutions to confirm free movement and correct assembly.
2. Cooling oil flow/ pressure test: With the engine on barring gear, or by priming the piston cooling system, pressurise the piston cooling oil circuit and confirm oil flows to the piston crown (verify at the tell-tale/return) and that the oil return opens; check the cooling oil pressure is at the maker's value and that the cooling gallery pressurises without leakage.
3. Confirm no oil leaks at the piston/crown joint and the pin seal by running the pump and inspecting.
4. Compression/ leak test: With the engine running, check compression and firing pressures and confirm no excessive blow-by.
5. Operational test: run the engine at load and monitor piston/crown temperature (via the cooling oil outlet temperature), exhaust temperature and the overall condition; confirm normal operation.

Main Engine Cylinder Head Stud Failure

Cylinder head studs are continuously subjected to high cyclic mechanical and thermal loads. Failure usually occurs due to a combination of the following factors:

• Overtightening or Uneven Tightening: If studs are tightened beyond their elastic limit or not tightened uniformly, excessive localized stresses are created. These stress concentrations promote fatigue cracking and eventual failure.
• Improper Pre-tensioning: Incorrect use of hydraulic jacks during tightening can result in either insufficient or excessive clamping force. Too little tension allows movement, while too much induces overstressing, both of which reduce stud life.
• Corrosion Fatigue: Leakage of cooling water or exposure to hot combustion gases can cause surface pitting on studs. These pits act as stress raisers, accelerating crack initiation under repeated loading.
• Excessive Vibrations and Impact Loads: Abnormal engine conditions such as knocking (detonation), poor fuel quality, or incorrect injection timing increase dynamic and shock loads on the studs, leading to fatigue failure.
• Material or Manufacturing Defects: Internal flaws such as inclusions, improper heat treatment, or poor material quality can weaken the stud, making it prone to premature failure even under normal loading.
• Thermal Stresses: Frequent and rapid temperature fluctuations during operation cause repeated expansion and contraction. This thermal cycling adds to mechanical fatigue and contributes to cracking.

Running the engine with one or more broken studs is unsafe and can lead to serious damage:

• Loss of Compression: The cylinder head may lift slightly during combustion due to insufficient clamping force, resulting in reduced peak pressure and loss of engine efficiency.
• Gas and Coolant Leakage: Combustion gases may escape externally (creating a fire hazard) or enter the cooling water spaces. Conversely, cooling water may leak into the cylinder, potentially causing hydraulic lock.
• Damage to Mating Surfaces: Relative movement between the cylinder head and liner/block leads to fretting and wear, damaging contact surfaces and requiring costly repairs such as machining or replacement.
• Overloading of Remaining Studs: The load previously shared by all studs is redistributed to the remaining intact ones. This significantly increases their stress levels, often resulting in progressive or chain failure.
• Failure of Cylinder Head Gasket or Seals: Uneven clamping force causes the gasket or O-rings to fail, worsening leakage and further reducing engine reliability.

Stud failure can be minimized by adopting proper maintenance and operational practices:

• Follow Manufacturer’s Specifications: Always use the correct hydraulic tightening pressures and follow the specified tightening sequence to ensure uniform load distribution.
• Regular Inspection and Monitoring: Periodically check studs for signs of wear such as necking, cracks (using non-destructive testing like dye penetrant), and corrosion, and replace defective studs in time.
• Proper Lubrication of Threads: Apply recommended lubricants or anti-seize compounds before tightening. This ensures accurate tensioning and prevents thread damage.
• Maintain Cooling Water Quality: Proper treatment of jacket cooling water prevents corrosion and scale formation, thereby protecting the studs from pitting and weakening.
• Avoid Thermal Shock: Operate the engine with gradual load changes and follow correct warming-up and cooling-down procedures to reduce thermal stresses.
• Control Vibrations and Combustion Quality: Maintain correct fuel injection timing, ensure good fuel quality, and regularly check engine alignment and mountings to minimize vibrations and shock loads.

ROCKING TEST OF A DECK ELECTRO-HYDRAULIC CRANE - PROCEDURE, CORRECT READINGS, INTERPRETATION

Procedure for the rocking test

1. Preparation: With the crane in full working order and hoisted clear of personnel, check the area below is clear and secured; confirm the safe working load (SWL), test load and the maker's procedure. Fit a certified proof load (typically 1.25 x SWL for the structure test).
2. Raise the load: Hoist the test weight a short distance; check the hoist/luff/ slew brakes hold the load and the crane is stable.
3. Carry out rocking: With the load suspended, rotate (slew) the crane to the extreme positions and rock the load by alternately raising and lowering the load and/or luffing the jib, so the jib and slew structure are alternately loaded and unloaded (rocking). This imparts the fatigue/ dynamic loading representative of service.
4. Observe and measure: Watch every structural member, the pivot/heeling pins, the slew bearing, the welds and the hydraulic system for abnormal deflection, noise, movement, cracking or oil leaks. Measure the jib-head deflection (below the load, from a fixed datum / taut wire) before and during the test.
5. Record: Note the deflection readings and any observations on the test sheet; compare against the maker's allowable deflection.
6. Complete: Lower and remove the load, re-inspect the structure (welds and joints) for cracks/deformation, and perform the operational checks (limit switches, load indicator, brakes, pressure relief) before the crane returns to normal SWL service.

How to ensure correct readings

• Use a calibrated/ certified test load and certified slings; check the load certificate.
• Use a properly calibrated measuring device (DTI, taut wire with rule, laser) mounted on a stable datum, not influenced by the crane frame movement.
• Zero the gauge at a defined reference (jib at the test position, no load) and read at the same position under load.
• Take readings in calm/ still conditions to avoid wind-loading error; weigh and confirm the exact applied load.
• Record at consistent points (same slew position, same load height) each time so the results are comparable.
• Repeat readings to confirm repeatability; use more than one observer/ position where possible.
• Ensure the test load is exactly the proof value and the crane is on a stable, level mooring.

Interpretation of readings for planning future overhauls

• If the deflection is within the maker's limit and returns to zero on removal of load (no permanent set): the crane is healthy; the readings establish a baseline for trending.
• If permanent set (residual deflection) or increasing deflection occurs with each rocking: indicates plastic deformation/fatigue, and the crane must be taken out of service.
• A consistently higher deflection than the baseline suggests loss of stiffness (crack, loosening of the slew pins/bearing, weld weakness) - schedule structural inspection/ NDT and plan for repair in the overhaul schedule.
• Increasing/ uneven deflection on one side may indicate bearing wear or a loose pivot, guiding overhaul of the slew/luff bearings.
• Repetitive cracking metal sounds or oil leaks signal the need for hydraulic seal/bearing overhaul.

The test thus provides a condition baseline and a trend against the maker's limits to schedule the crane's structural and mechanical overhauls (pins, bearings, slew ring, hydraulic seals) rather than awaiting a failure.

FITTING A SPARE BOTTOM END BEARING (WHITE METAL CRACKED) AND TESTS BEFORE RETURNING TO SERVICE

1. Preparation: With the medium-speed diesel generator stopped and secured, bar/lock the engine, drain the sump, and obtain the maker's manual and a genuine spare bearing (white-metal/ bimetal or tri-metal shell, machined to the correct size). Tag the machine not-to-run.
2. Gain access: Remove the sump/ bedplate door, the big-end bearing cap bolts and lift the connecting rod bottom end. Position the crank so the big-end is accessible (usually at bottom centre). Crank pin should be inspected.
3. Remove the old bearing: Withdraw the two bearing caps/ shells (the big-end is a split "house" formed by the rod's big-end housing bottom cap and the crank-pin cap). Remove the old white metal ('lead/babbit' or leaded-bronze or trimetal layers) carefully - it may be bonded to the shell by swaging. Note the clearance.
4. Inspect the crank pin/ journal and the bearing housing: check for scoring, pitting, out-of-round (micrometer), and that the housing mouths are clean. Correct any damage.
5. Fit the spare bearing: Fit the bearing shells into the two halves of the big-end housing; the bearing must be a clearance fit/ lightly pressed as per maker. Fit new shims/ adjust the cap to set the correct diametral clearance (typically 0.025-0.10 mm per 25 mm of journal diameter, but per maker). Set the bearing so the two shell halves have the correct end float/ niminal end clearance and that the crank pin rotates without binding. Torque the big-end bolts to specification using a torque wrench, in the correct sequence; always fit new bolts/ nuts if the manual requires.
6. Check the big-end bolts stretch/ torque and the locking/ split pins; check the flywheel/ crank end clearance as required.
7. Refit the sump/ crankcase doors, refit oil connections and refill with clean lubricating oil to the correct level.

1. Bar the engine over by turning gear, checking free rotation and that the bearing does not bind or rub at any position (feel for tight spots; there should be a slight shake/ vertical float).
2. Check/ set the big-end bearing vertical clearance within limits (use the correct feeler/gauge).
3. Prime the lubrication system: run the lube oil pump (or bar-over with oil supply) to confirm oil reaches and wets the big-end bearing and that the oil pressure/temperature are normal and no leaks at the new joint.
4. Cold-crank check (without ignition/ or with fuel off) using the starter to confirm oil pressure is established.
5. Vibration/noise: run the generator at low load initially, monitoring bearing temperature (should remain cool and stable), vibration, and oil pressure; then load up gradually to full load and monitor for a steady bearing temperature within limits.
6. Perform a compression/ indicator check if accessible and confirm smooth running, no knocking, and that oil pressure stays within specification at load.
7. After a running-in period, re-check the big-end bolt torque and the oil filter for debris (the bearing bedding-in may shed small particles).

(a) Procedure for Complete Inspection of a Bottom End Bearing:
Planning:

• Ensure you have sufficient time, manpower, and all necessary tools, spares, and the manufacturer's manuals.
• Organize the workspace, ensuring all safety measures are in place.

With the engine shut down, lubricating oil pump stopped, start air locked off, turning gear engaged, Risk assessment and a permit to work obtained, proceed as follows for checking the condition of the bottom end bearing surface of a large slow speed engine.

• Open the crankcase door at the relevant cylinder and ventilate, as the crankcase is an enclosed space (Follow the enclosed space entry procedure).
• Turn the relevant cylinder to BDC and check the bearing clearance. This is because, after squaring up, the clearance should be the same.

To remove the Bottom end bearing (bottom-side)

• Now turn the cylinder to TDC. Mount eyebolts on each side of the crankpin bearing cap and suspend two tackles from the lifting brackets in the athwartship direction.
• Using shackles and wire ropes, hook on the tackles and haul tight.
• Loosen the crankpin bearing studs using hydraulic jacks. Remove the palm nuts.
• Lower the bearing cap while carefully ensuring that the studs do not damage the crankpin journal. Land the bearing cap on a couple of planks placed in the crankpit.
• Using another tackle mounted on top of the crankcase door, carefully lift the bearing cap out of the crankcase and place it on wooden planks.

To remove the Bottom end bearing (top side)

• Fit four guide shoe retaining blocks into the crosshead guides. This will prevent the crosshead and conrod from moving down when the engine is turned.
• Wrap a strop around the bottom of the conrod and attach it to a chain block mounted on the side of the engine.
• Turn the engine while pulling the lower part of the conrod with the lifting tackle so that the crankpin turns out of the top half of the bearing. Ensure that the crankpin does not foul on the top edge of the bearing.
• The crankshaft can be turned to the bottom dead centre, and the top half of the bearing examined/ removed.

Inspect the bearing surface for any signs of scoring, pitting, wiping, ovality, cracks, or corrosive attack. Take photographs of the bearing and make relevant paperwork. The clearance of the bearing should be recorded before opening and after square up. Square up the bearing in the reverse order of dismantling.

(b) Precautions to be Taken:

• Inspect the condition of all lifting gear, including eyebolts, shackles, and chain blocks, before use. Ensure their load capacity is suitable for the weight being lifted.
• Inspect the hydraulic jack and its hoses for leaks and proper functionality.
  
• Ensure the work area is clean, especially if there are no oil spills on the platform to prevent accidents or contamination.
  
• Ensure all personnel wear proper personal protective equipment (PPE), including safety belts when working inside the crankcase.
  
• Strictly follow engine isolation procedures (lockout/tagout), ensuring the engine cannot be started accidentally.
  
• Ensure no personnel are inside the crankcase during engine turning the engine using turning gear
• Precautions to be taken while lowering and taking out the bearing so that threads, bearing shell, and crankpin are not damaged
• Protect the crankshaft journal and bearing surfaces from dirt and damage during removal and inspection.
  
• Apply the correct hydraulic pressure when loosening and tightening nuts.
  

(c) Tests Carried Out on Completion of Survey and Reassembly:

• Measure the bearing clearance to ensure it is within limits as specified in the maker's manual
• Check the crankshaft deflection to confirm proper alignment and that there are no undue stresses.
  
• Start the lube oil pumps and check for proper oil flow to the bearings
  
• Turn the engine on the turning gear and monitor amperage to detect any obstruction.
  
• Test run the engine on air, followed by a load test. During operation, monitor the bearing temperature closely to detect any abnormalities.
  
• After stopping the engine, inspect for any white metal fragments, which could indicate wear or damage.
  
• Check for hot spots that could signify improper lubrication or bearing fitment issues.
  

Actions to be Taken When New Bunkers Differ Significantly from Existing Fuel

When the density of the new fuel differs from the existing fuel, the following steps are necessary:

• Adjustment of Purifier Settings: The gravity disc size (in manually controlled purifiers) must be selected according to the new fuel density. For automatic systems such as ALCAP purifiers, the operating parameters should be adjusted to maintain proper oil-water separation.
• Accurate Fuel Quantity Calculation: Since fuel inventory is often measured by volume, the new density must be used to recalculate the actual mass of fuel on board. This is important for both fuel management and stability calculations.
• Monitoring Centrifuge Performance: The oil-water interface inside the purifier should be closely monitored to prevent either oil loss through the water outlet or water carry-over into the clean oil side.

Variations in viscosity directly affect fuel atomization and combustion quality. The following actions should be taken:

• Adjustment of Viscosity Controller: The fuel oil heater and viscosity control system must be set so that the fuel reaches the required viscosity (typically 12–14 cSt) at the engine inlet for efficient atomization.
• Temperature Management: Proper heating of fuel lines must be ensured. Trace heating systems should be checked and maintained to prevent poor flow characteristics or “waxing,” especially if the new fuel has a higher pour point.

Cat fines are highly abrasive and can cause severe engine wear if not properly removed. The following precautions are essential:

• Maximizing Purification Efficiency: Operate purifiers at reduced throughput or in series (if arrangements permit) to increase residence time, thereby improving the removal of fine particles.
• Settling Tank Management: Maintain the settling tank temperature at approximately 85–90°C to promote the settling of cat fines at the bottom, which can then be drained periodically.
• Frequent Filter Inspection: Increase the frequency of inspection and cleaning of fuel oil filters, including automatic backwash filters, to prevent passage of abrasive particles to the engine.

Sulphur content has both operational and regulatory implications:

• Regulatory Compliance (MARPOL): Ensure that the sulphur content of the fuel complies with the limits applicable to the trading area (e.g., 0.50% globally or 0.10% in Emission Control Areas).
• Cylinder Lubrication Adjustment: Adjust the cylinder oil feed rate and select the appropriate Total Base Number (TBN). High sulphur fuels require higher TBN oils to neutralize acidic products, whereas low sulphur fuels require lower TBN oils to avoid deposit formation.
• Fuel Segregation: Avoid mixing the new fuel with existing fuel unless compatibility is confirmed, as incompatible fuels can form sludge and cause operational problems.

Excess water in fuel can lead to poor combustion and damage to engine components. The following measures should be taken:

• Settling and Draining: Allow the fuel to settle in the settling tank and regularly drain accumulated water from the bottom.
• Monitoring Purifier Operation: Ensure that the purifier is functioning effectively for water separation. Keep a close watch on water-in-oil alarms and discharge quality.
• Use of Homogenizer (if fitted): A homogenizer should only be used if purification is already optimized and water content remains within acceptable limits. It should not be relied upon as a primary method of water removal.

1. Overcharge of Refrigerant

An overcharged system contains excess refrigerant, which adversely affects condenser performance and system pressures. The following indications are observed:

• The liquid level in the condenser becomes excessively high, resulting in a reduction of the effective condensing surface area. This leads to an increase in saturation temperature and pressure.
• The condenser pressure gauge shows high readings, indicating elevated system pressure.
• The high-pressure cut-out switch may activate, automatically stopping the compressor to prevent damage.
• Both suction pressure and discharge pressure are higher than normal, reflecting the overall overload condition of the system.

2. Undercharge of Refrigerant

An undercharged system has insufficient refrigerant, leading to poor cooling performance and abnormal compressor operation. The typical indications include:

• The compressor runs at a higher temperature due to high superheat at the suction side, which reduces its efficiency.
• Both suction and discharge pressures are lower than normal.
• Large vapour bubbles appear in the liquid sight glass, indicating insufficient liquid refrigerant flow.
• The condenser gauge shows low pressure readings.
• The compressor motor current (ammeter reading) is lower than normal, due to reduced load.
• There is a rise in the temperature of the refrigerated space, indicating inadequate cooling.
• The compressor runs continuously or for extended periods in an attempt to maintain the desired temperature.

3. Air Ingress into the System

The presence of air (non-condensable gases) in the refrigeration system affects heat transfer and pressure conditions. The following symptoms are observed:

• The compressor may overheat, accompanied by high discharge pressure, even though the condensing temperature may remain normal.
• Small air bubbles may be visible in the liquid sight glass.
• The condenser pressure tends to be higher than normal, due to the presence of non-condensable gases.
• Cooling efficiency is reduced, causing the compressor to run for longer durations.
• The condenser pressure gauge pointer may fluctuate or jump irregularly, indicating unstable system conditions.

1. Rectification of Overcharge

Causes:

• Excess refrigerant charged into the system.
• Air in the system may sometimes give a false indication of overcharge.

Corrective Actions:

• Remove excess refrigerant by connecting a recovery cylinder to the liquid line charging valve. Run the compressor and carefully discharge refrigerant into the cylinder.
• Purge any air present in the system to ensure correct pressure conditions.
• If icing is observed in control components (such as regulators), carry out defrosting using appropriate methods.

2. Rectification of Undercharge

Causes:

• Leakage of refrigerant from components such as shaft seals, flanges, valve glands, or joints.
• Blockage in the expansion valve strainer.
• Partial restrictions in filters, driers, or evaporator passages.

Corrective Actions:

• Identify and repair all refrigerant leaks in the system.
• Clean or replace blocked filters and driers to restore proper flow.
• After rectification, charge the system with the required amount of fresh refrigerant to restore normal operation.

3. Rectification of Air Ingress

Causes:

• Entry of air during improper charging procedures.
• In low-pressure systems (such as those using certain refrigerants), air may leak into the suction side when system pressure falls below atmospheric pressure.

Corrective Actions:

• Purge air from the system via the condenser, as air (being non-condensable) accumulates at the top of the condenser above the հեղ liquid refrigerant.
• Keep the condenser cooling active, and vent out the air carefully through the purging line.
• If required, connect a collecting cylinder to safely remove the air.
• After purging, close all valves properly and check the refrigerant level.
• Recharge the system if necessary, and restart the compressor while observing all safety precautions.

Risk on board a ship refers to the combination of the likelihood of an event occurring and the potential consequences of that event. It encompasses the probability of harm to people, property, or the environment due to hazards present in the marine environment. As almost every task performed on a ship involves some level of risk, it is essential to analyze tasks for potential dangers and adopt measures to mitigate risks effectively.

Risk Assessment Process

Risk assessment involves the systematic evaluation of tasks to identify hazards, determine the likelihood of their occurrence, and evaluate their consequences. It aims to ensure that adequate precautions are in place to prevent accidents. The process involves the following key steps:

1. Identifying Hazards

Hazards are anything with the potential to cause harm. In the marine environment, these include:

• Weather conditions
• Inadequate lighting or ventilation
• Damaged tools or equipment
• Handling heavy weights
• Electrical hazards and moving machinery
• Slippery surfaces and enclosed openings
• Fumes from chemicals, working at heights, and high-pressure systems like steam or gas
• Noise and sharp objects

2. Determining Likelihood

The likelihood of an event is assessed as:

• Unlikely
• Possible
• Likely
• Very frequent

3. Evaluating Consequences

Consequences refer to the outcomes of an event, which can be:

• Human Consequences: Injuries or fatalities
• Environmental Consequences: Pollution or ecological damage
• Property Consequences: Damage to machinery, cargo, or facilities

Methods such as incident history or theoretical modeling can be used to evaluate consequences. A risk profile matrix, combining likelihood and consequences, helps to categorize the severity of the risk.

As a Second Engineer, effective methods for identifying and addressing risks include:

1. Observation and Inspection: Regularly inspect equipment, tools, and working conditions to identify visible hazards.
2. Incident History Review: Examine past accidents to understand root causes and consequences.
3. Crew Feedback: Encourage open communication with the crew to report potential hazards and unsafe practices.
4. Job Safety Analysis (JSA): Break down each task into steps, identify associated hazards, and implement controls.
5. Risk Mitigation Measures: Employ controls such as:
   • Risk Avoidance: Cease tasks with unmanageable risks.
   • Risk Reduction: Implement engineering controls, safety devices, and safe work practices.
   • Risk Transfer: Share risk responsibility through insurance or contracts.

Once risks are identified, they are either accepted or treated:

• Risk Acceptance: Acceptable low-level risks allow work to proceed without additional controls.
• Risk Treatment: Moderate or high risks require reduction measures before work begins. This involves:
  • Modifying work procedures
  • Providing personal protective equipment (PPE)
  • Implementing administrative controls

I. Safety Precautions

Safety is the absolute priority when dealing with the confined spaces and hazardous atmospheres of an STP.

A. Pre-Inspection Measures

• Permit to Work (PTW): A formal "Confined Space Entry Permit" must be obtained and signed by authorized personnel.
• Risk Assessment: Identify hazards including toxic gases (Methane H2S), oxygen deficiency, electrical risks, and biological contamination.
• Isolation (LOTO):
  • Electrical: De-energize and Lock-Out/Tag-Out (LOTO) all pumps, blowers, and UV units at the main switchboard.
  • Fluid: Close and blank off all inlet/outlet valves to prevent accidental flooding.
• Ventilation: Use portable blowers or eductors to purge gases. Ventilation must remain active throughout the entire procedure.
• Gas Testing: Use a calibrated gas detector to confirm:
  • Oxygen (O2): 20.8% ± 1%.
  • Flammable Gases: Below 1% LEL (Lower Explosive Limit).
  • Toxic Gases: Check for H2S and Carbon Monoxide (CO).
• PPE Requirements: Chemical-resistant coveralls, gloves, safety boots, goggles, and personal multi-gas detectors. A Safety Harness with a lifeline/tripod system is mandatory.
• Standby Personnel: A trained "Standby Man" must remain at the entry point to maintain communication and trigger the Rescue Plan if necessary.
• Cleaning: The unit must be drained, flushed, and cleaned of all sludge/scum before entry to minimize biological risks.

B. During & Post-Inspection

• Continuous Monitoring: Maintain gas testing and constant verbal/visual contact with the standby man.
• Hot Work Ban: No welding or cutting is permitted without additional specific permits.
• Tool Control: Inventory all tools before and after to prevent "Foreign Object Damage" (FOD).
• Closing Up: Confirm all personnel are out before securing hatches, re-energizing equipment, or reopening valves.

II. Inspection Procedure

Phase 1: Preparation

1. Review Documentation: Study the STP manual, previous reports, and schematics.
2. Isolate & Clean: Follow the LOTO procedures and perform a deep clean of internal surfaces for better visibility.
3. Atmospheric Check: Ensure the environment is safe via ventilation and gas testing.

Phase 2: Execution (Entry)

1. Authorized Entry: Enter only after the permit is validated.
2. Systematic Survey: Move through the treatment stages (Primary → Secondary → Tertiary), documenting findings with photos and measurements.

Phase 3: Documentation & Recommissioning

1. Reporting: Create a detailed report of corrosion, wear, and structural integrity.
2. Refilling: Follow manufacturer guidelines to gradually return the plant to service.

III. Components to be Inspected

A. Primary Treatment Section

• Comminutor/Macerator: Check cutters/blades for sharpness, wear, and blockages. Inspect the motor mounting.
• Settling Tanks: Inspect walls and floors for cracks or coating failure. Check that Baffles and Weirs are aligned and free of scale.
• Sludge Hoppers: Ensure hoppers/cones are free of corrosion and blockages.

B. Secondary Treatment (Biological)

• Aeration Tank: * Diffusers: Check for clogging, damage, or uneven air distribution.
  • Bio-media: Look for signs of "channeling" or excessive biomass growth.
  • Mixers: Inspect propeller blades and shaft alignment.
• Secondary Clarifier: * Scrapers: Check for smooth operation and mechanical wear.
  • Launders: Ensure weirs are perfectly level to maintain uniform flow.

  C. Tertiary Treatment & Disinfection

  • Chlorination Unit: Inspect contact tank walls and baffles for scale buildup.
  • UV Disinfection: Check quartz sleeves for fouling/cracks and test automatic wipers.
  • Filters: Inspect filter media for integrity and ensure the underdrain system is not blocked.

  D. General Components (System-Wide)

  • Internal Piping: Check for leaks, internal corrosion, and valve seating integrity.
  • Sensors: Clean and inspect pH, Dissolved Oxygen and level probes.
  • Structural: Inspect all internal supports, brackets, and access manholes/gaskets for signs of fatigue or thinning.

(a) Feed Contamination by Oil from Heating Coil Drains

Prevention Measures:

• Ensure heating coil drains are led to an observation tank or inspection glass before discharging overboard, so oil presence can be detected.
• Provide and maintain steam traps and drain valves in good condition to avoid oil leakage into feed systems.
• Fit non-return valves and isolating valves between heating coils and feedwater system.
• Regularly inspect and test coil integrity to detect leaks early.
• Avoid direct connection between heating coil drains and feedwater system without monitoring arrangements.

(b) Internal Corrosion

Prevention Measures:

• Maintain correct boiler water treatment program to control pH and dissolved oxygen levels.
• Use oxygen scavengers and chemical dosing as per manufacturer’s recommendations.
• Maintain feedwater temperature in the cascade tank at about 85°C to aid oxygen release.
• Keep feed tank and cascade tank lids/manholes closed to prevent air ingress.
• Carry out regular blowdown to remove sludge and maintain proper alkalinity.
• Inspect internal surfaces periodically and renew protective coatings if applied.

(c) Furnace Blowback

Prevention Measures:

• Always carry out proper pre- and post-purging to clear combustible vapors from the furnace.
• Maintain correct air–fuel ratio by ensuring proper functioning of air dampers, fuel regulators, and controllers.
• Inspect and clean atomizers/burners to ensure fine fuel spray and complete combustion.
• Check fuel viscosity and temperature to maintain correct atomization.
• Avoid ignition attempts in a furnace containing unburnt fuel; purge thoroughly before re-lighting.
• Ensure proper sequence and interlock functioning in the burner management system.

(d) Uptake Fire

Causes:

• Accumulation of oily soot on tube surfaces due to incomplete combustion.
• Poor circulation through tubes causing overheating.
• High tube metal temperatures (>700°C).

Prevention Measures:

• Carry out regular soot blowing and periodic washing of exhaust gas boilers to remove soot deposits.
• Maintain proper air–fuel ratio and ensure complete combustion by checking damper and fuel control systems.
• Ensure adequate steam and water flow in generating and superheater tubes to maintain good heat transfer and circulation.
• Keep auxiliary blower running (manual mode if needed) to maintain airflow and prevent high exhaust temperatures during cut-off periods.
• Maintain fuel oil injection viscosity between 12–13 cSt for correct atomization.
• Incorporate extra soot-blowing routines when using fuels prone to high carbon deposition.

To:

The Superintendent,

MV. The Great,

Alpha Pvt. Ltd.,

Singapore.

From: (Name/Rank)

Date:

Subject: Breakdown of Main Refrigeration Plant – Cargo Provisions

Dear Sir,

This report details the breakdown of the main refrigeration plant for cargo provisions on DD/MM/YYYY at 0900 hours.

The duty engineer discovered a low refrigerant level in the system and initiated a charging procedure. However, during charging from the low-pressure (LP) side, the liquid valve on the refrigerant gas bottle was inadvertently opened instead of the gas valve. Upon starting the compressor, abnormal noise was detected, resulting in the compressor tripping.

A subsequent inspection revealed the following:

• The compressor was difficult to turn manually.
• Examination of the crankcase revealed a bent connecting rod and fragments of piston rings.
• Complete dismantling of the compressor showed damage to the connecting rod, piston assembly, liner, and valve plate. The crankshaft was found to be undamaged.

The following repair actions were undertaken:

• The crankshaft was checked for bending and trueness and found to be in good condition.
• All compressor parts were thoroughly cleaned.
• The attached lubricating oil (L.O.) pump assembly was inspected and found to be in good working order.
• The piston and connecting rod assembly, liner, and valve plate were replaced with new parts.
• All separators and filter dryers were cleaned.
• The compressor was reassembled.
• The compressor oil was renewed.
• The system was purged of air.

The primary cause of the breakdown was the incorrect operation of the valves on the refrigerant gas bottle, leading to liquid refrigerant entering the compressor.

To prevent similar incidents, the following measures have been implemented:

• The valves on all refrigerant gas bottles have been clearly marked with different colours and labels to improve identification.
• All crew and engineers have received further instruction and briefing on the correct procedure for refrigerant charging. Particular emphasis was placed on the dangers of introducing liquid refrigerant into the compressor.
• A copy of the approved refrigerant charging procedure is now prominently displayed near the compressor and gas bottles.
• Close monitoring of the refrigeration plant will be maintained. Regular checks and detailed logs will be recorded.
• No refrigerant charging will be undertaken without prior notification and authorisation from the Chief Engineer or Second Engineer.

Yours Sincerely,

(Your Name/Rank)

Trouble Spots in a Basic Air Conditioning Unit

• Refrigerant Leakage: Commonly occurs at the compressor shaft seal, condenser, dryer, oil separator, evaporator coils, or damaged pipes.
• Condenser: Insufficient water or air flow and dirty tubes may cause high-pressure (HP) trip.
• Filters: Blocked intake and recirculation filters lead to poor airflow.
• Dryer & Expansion Valve: Can experience icing or short cycling, causing system inefficiencies.
• Evaporator Coil: Dirt accumulation leads to poor heat transfer and icing.
• Electrical Problems: Malfunctioning of LP/HP trips, oil differential pressure switches, thermostats, solenoid valves, motors, or fans.
• V-Belts: Wear and breakage can disrupt fan or motor operation.
• Expansion Valve Malfunction: Leads to improper cooling.
• Compressor Issues: Damage due to liquid refrigerant entering the suction line or inadequate lubrication.

(i) How the problem of increase in humidity of cooled air is overcome?

In hot climates, when cooling air, its relative humidity may rise to uncomfortable levels (up to 100%). To address this issue:

De-Humidification Process:

• The air is overcooled first to reduce its temperature below the dew point, causing the excess moisture to condense out of the air.
• The cooled, dry air is then reheated to bring it back to a comfortable temperature and humidity level suitable for human comfort.
• This ensures the air supplied to the space is not excessively humid.

(ii) How discomfort caused by the excessive drying effect of heated air is overcome?

In cold climates or winters, air may become excessively dry when heated, leading to discomfort for occupants. To manage this:

Humidity Control Through Humidification:

• A humidifier is fitted inside the Air Handling Unit (AHU).
• The humidifier injects steam or water mist into the heated air to maintain a relative humidity of approximately 40%, which is considered comfortable.
• This ensures that the heated air does not cause dryness in the indoor environment, improving comfort for occupants.

CO₂ Bottle Weighment – Observations, Causes, and Required Actions

During the weighing of CO₂ bottles used for total flooding of the engine room, if it is found that some bottles have lost more than the permissible limit (generally more than 10% of their original charge), it is considered a serious safety concern. Such a deficiency can compromise the effectiveness of the fixed fire-fighting system and must be addressed immediately.

Reasons for Reduced CO₂ Capacity

The reduction in CO₂ content within the bottles can occur due to several reasons:

• Leaking Valves: This is the most common cause. Leakage may occur from the main valve or discharge head due to worn-out seals, dirt or debris on the valve seat, or improper tightening.
• Corrosion of Cylinder: External or internal corrosion can weaken the cylinder wall, leading to very fine pinhole leaks through which gas can gradually escape.
• Damaged or Defective Bursting Disc: The bursting disc is a safety device designed to rupture at excessive pressure. If it becomes weakened, fatigued, or damaged, it may allow slow leakage of CO₂.
• Improper Sealing After Maintenance: If the bottles were previously serviced or tested, incorrect reassembly or poor sealing of connections may result in gradual gas loss.

Checks and Tests Before Refilling

Before refilling any CO₂ bottle, it is essential to ensure that the cylinder is structurally sound and safe for reuse:

• External Visual Inspection: Examine the cylinder for dents, pitting, corrosion, or any signs of overheating.
• Internal Inspection: Use suitable methods such as a borescope to check for internal corrosion, scaling, or damage.
• Hydrostatic Pressure Test: The cylinder is filled with water and pressurized (typically up to 1.5 times the working pressure) to check for leaks or permanent deformation.
• Verification of Tare Weight: The empty weight of the cylinder must be confirmed to ensure that the correct quantity of CO₂ is filled.
• Valve Overhaul: The valve assembly should be dismantled, inspected, and fitted with new seals, O-rings, and a properly functioning bursting disc.

Frequency of Inspection and Testing

As per IMO guidelines (MSC.1/Circ.1318/Rev.1) and SOLAS requirements, the following inspection schedule must be followed:

• Weighing / Level Checking: All CO₂ cylinders must be weighed or checked using ultrasonic level indicators at least once every two years. If any cylinder shows a loss exceeding 10% of its original content, it must be refilled or replaced.
• Hydrostatic Testing and Internal Inspection:
  • At least 10% of the total number of cylinders must undergo internal inspection and hydrostatic testing every 10 years.
  • By 20 years, all cylinders (100%) must have been tested at least once.
  • After this period, all cylinders must be tested at intervals not exceeding 10 years.

To,

The Superintendent Engineer

MV Alexa

ABC Pvt Ltd

Singapore

Subject: Report on Damage Suffered by Main Engine Exhaust Valves

Dear Sir,

I am writing to inform you about the premature failure of three exhaust valves in the main engine over the past four months. Below is a detailed report addressing the issue:

• The issue first became evident in Unit No. 3 of the main engine, where we observed a sudden increase in the exhaust temperature. The deviation was more than 70 degrees compared to the other units. This abnormality was confirmed by the local temperature gauge.
• Upon conducting a main engine performance analysis, it was noted that both Pcomp (compression pressure) and Pmax (maximum pressure) were lower than normal, suggesting a potential exhaust valve leak.
• During the next port call, we opened the exhaust valve of Unit No. 3 and discovered significant cracking and corrosion at the seating face. Subsequent inspections of the exhaust valves in Units 6 and 7 revealed similar issues, confirming a pattern of damage across multiple units.

• Recognizing that the damage might be due to the poor quality of fuel oil, particularly high levels of vanadium and sodium, we immediately reduced the engine's speed and load to lower the exhaust temperature and mitigate further hot corrosion.
• We conducted inspections of the exhaust valves in other units, replacing the affected valves with overhauled spares.
• The fuel oil in use was switched to an alternative tank with lower vanadium and sodium content, based on available laboratory analysis. Additionally, we sent samples of the recent oil (fuel that caused the issue) to a laboratory for testing, as the relevant report was missing from our files.

• The combustion of fuel oil containing high levels of vanadium and sodium can lead to the formation of sodium vanadate, which has a low melting point of around 450°C. These molten compounds are highly corrosive and can attack components such as exhaust valves and piston crowns.
• Fuel oil with a high asphaltene content may result in incomplete combustion, leading to increased deposits in the combustion chamber and exhaust gas system, further damaging exhaust valves and their seats.
• Scale deposits within the cooling pockets of the exhaust valves can reduce their cooling efficiency, leading to overheating, material degradation, and hot corrosion.
• Poor combustion timing or quality, such as late or incomplete combustion, can lead to higher exhaust temperatures, contributing to hot corrosion.

• Ensure the use of fuel with minimal vanadium, sodium, and asphaltene content. Laboratory analysis of bunker fuel should be carefully retained onboard for reference.
• Regular maintenance of fuel injection devices is essential to prevent late combustion and the associated rise in exhaust temperature.
• Adequate cooling of exhaust valve seats should be maintained through proper treatment of cooling water and regular cleaning of cooling pockets to prevent scale build-up
• When laboratory reports indicate high sodium and vanadium levels in the fuel, appropriate corrective actions should be taken before and during engine operation to prevent damage.

Please feel free to contact me for further discussion or clarification on the matter.

Yours sincerely,

[Your Name]

Second Engineer

MV Alexa

• Any initial design flaws or manufacturing defects that may have been missed during the initial construction and testing phases will likely manifest themselves during the initial operational period
• During the initial trial, the engine is slowly started, and various parameters are monitored. The speed of the engine is gradually increased, and all parameters are monitored.
• The inspection of the gearbox after commissioning will reveal the characteristics of the gearing system as to how it responds to various speeds and load
• The strength of the gearing system is tested during actual operation. Any design fault or defect may be indicated during the trial run itself.
• The first inspection reveals the compatibility of gearing with the engine and the propeller. Based on the result of various inspections, parameters like oil pressure, flow volume, cooling required for the oil, torque, maximum stress levels, and vibration levels are identified.
• This will also enable the setting up of various running parameters and the frequency of inspection required

• The gear teeth should be carefully inspected for cracks, pitting, or signs of misalignment. The contact pattern on the gear teeth reveals how well the gears are meshing. Misalignment can lead to uneven wear, increased stress, and eventual failure of the gears.
• The gear shafts should be checked for bending or cracks, which could result from overloading or misalignment during installation. Any defects in the shaft could compromise the transmission of power and lead to vibration and further damage.
• The condition of the shaft seals should be inspected for wear or damage. A broken or worn-out seal can lead to oil leakage, which not only reduces lubrication efficiency but can also lead to contamination of the oil with dust or water, accelerating wear and corrosion.

Possible defects that might be found during this inspection include increased gear backlash, which can affect torque transmission and lead to excessive stress, and shaft end play, which can cause misalignment and vibration. Smoke from seals or the breather can indicate overheating, suggesting inadequate lubrication or excessive friction within the gearbox.

1. Pitting: This is a form of localized corrosion where small holes form on the metal surface of the gears due to cyclic loading. These pits can grow over time, leading to larger surface defects and reduced gear efficiency.
2. Scuffing: If the oil film between the gear teeth fails, metal-to-metal contact can occur, leading to scuffing. This process involves the tearing apart of welded metal on the tooth surfaces, resulting in rough, damaged surfaces.
3. Intense Wear: If the gear teeth tips and roots have not been properly stress-relieved or rounded, they can dig into each other, causing excessive wear and reducing the lifespan of the gears.
4. Abrasive Wear: This occurs when foreign particles are present in the lubricating oil, leading to scoring or scratch marks on the gear surfaces. This type of wear can be minimized by ensuring that the oil is clean and properly filtered.
5. Flaking: Flaking is typically seen in case-hardened gears and can result from poor heat treatment or conditions that stress the metal beyond its yield point. Small flakes of metal break away from the gear surface, leading to surface degradation.
6. Plastic Flow: High local stresses can cause the metal to deform plastically, leading to a wave-like distortion ahead of the contact point. This can result in subsurface fatigue failure, where flakes of metal shear off, further damaging the gear surface.

Risk on board a ship refers to the combination of the likelihood of an event occurring and the potential consequences of that event. It encompasses the probability of harm to people, property, or the environment due to hazards present in the marine environment. As almost every task performed on a ship involves some level of risk, it is essential to analyze tasks for potential dangers and adopt measures to mitigate risks effectively.

Risk Assessment Process

Risk assessment involves the systematic evaluation of tasks to identify hazards, determine the likelihood of their occurrence, and evaluate their consequences. It aims to ensure that adequate precautions are in place to prevent accidents. The process involves the following key steps:

1. Identifying Hazards

Hazards are anything with the potential to cause harm. In the marine environment, these include:

• Weather conditions
• Inadequate lighting or ventilation
• Damaged tools or equipment
• Handling heavy weights
• Electrical hazards and moving machinery
• Slippery surfaces and enclosed openings
• Fumes from chemicals, working at heights, and high-pressure systems like steam or gas
• Noise and sharp objects

2. Determining Likelihood

The likelihood of an event is assessed as:

• Unlikely
• Possible
• Likely
• Very frequent

3. Evaluating Consequences

Consequences refer to the outcomes of an event, which can be:

• Human Consequences: Injuries or fatalities
• Environmental Consequences: Pollution or ecological damage
• Property Consequences: Damage to machinery, cargo, or facilities

Methods such as incident history or theoretical modeling can be used to evaluate consequences. A risk profile matrix, combining likelihood and consequences, helps to categorize the severity of the risk.

As a Second Engineer, effective methods for identifying and addressing risks include:

1. Observation and Inspection: Regularly inspect equipment, tools, and working conditions to identify visible hazards.
2. Incident History Review: Examine past accidents to understand root causes and consequences.
3. Crew Feedback: Encourage open communication with the crew to report potential hazards and unsafe practices.
4. Job Safety Analysis (JSA): Break down each task into steps, identify associated hazards, and implement controls.
5. Risk Mitigation Measures: Employ controls such as:
   • Risk Avoidance: Cease tasks with unmanageable risks.
   • Risk Reduction: Implement engineering controls, safety devices, and safe work practices.
   • Risk Transfer: Share risk responsibility through insurance or contracts.

Once risks are identified, they are either accepted or treated:

• Risk Acceptance: Acceptable low-level risks allow work to proceed without additional controls.
• Risk Treatment: Moderate or high risks require reduction measures before work begins. This involves:
  • Modifying work procedures
  • Providing personal protective equipment (PPE)
  • Implementing administrative controls

Sketch arrangement: Two identical hydraulic power units (motors/pumps) and control, each providing 50% of the full steering torque, arranged so that either unit alone can produce full rudder movement:

• Two separate hydraulic circuits (A and B), each with: a motor-driven pump, a control/telemotor unit, a 3-way directional (four-way) control valve, and connecting lines to a common or twin ram of the rudder actuator.
• The two rams (actually two hydraulic force/actuator cylinders or one cylinder with two pistons) are coupled so that both units act on the same rudder stock. Each unit is capable, on its own (one ram taking the load), of meeting SOLAS requirement for full rudder angle (35 deg port to 35 deg starboard) and speed from 35 to 30 deg in 28 seconds, and also to steer at max service speed.
• On failure/ tripping of one unit, the other unit automatically takes over (changeover is automatic to prevent loss of steering) and drives the ram to rams that are still pressurised (the non-faulty circuit), giving specified angle/speed from a single unit.
• Independent telemotor control for each unit with automatic changeover; power from independent electrical circuits/sources.

Description: This arrangement satisfies the single-failure criterion, i.e., if one power actuating system (one 50% unit) fails, the remaining unit continues to steer the ship with the required performance, and a failure within the control system or power supply of one set does not make the other set ineffective. The two units are cross-connected at the actuator so that they share a common rudder stock but are hydraulically independent.

• Run only at reduced but full-service capability: one unit gives the required rudder angle but at reduced actuating capacity; maintain reduced speed and manoeuvre with caution, expecting slower rudder rates.
• Confirm the automatic changeover/ manual changeover to the live unit is correct; ensure the failed unit is isolated (motor off, valves set) to hold pressure.
• Check the working (live) ram oil level/pressure and topping-up arrangement; the live ram must be kept full of oil to avoid cavitation and loss of power.
• Monitor the live unit temperature and take measures to prevent overheating of its pump/ motor; arrange cooling if needed.
• Keep the rudder stock centre/ area clear; do not obstruct steering.
• Because only one ram carries the load, the live ram and its actuating cylinder/ hanger must be checked for excessive temperature and vibration; avoid prolonged continuous operation at maximum angle.
• Keep a continuous watch on the steering, and if possible reduce to a manoeuvring condition, inform bridge and maintain emergency alarm readiness.
• Carry out a running test at the earliest safe opportunity to confirm the single-unit performance is available, and restore the second unit as soon as possible.

1. Simulation test (changeover test): Simulate failure of one unit (e.g. trip/main-fault the unit switch, or open its circuit) and verify that the other unit automatically supplies the full specified movement; check that the changeover is automatic and within time limits.
2. Functional/ operational test: With only one unit in service (the other isolated), drive the rudder from hard-over to hard-over and verify rudder angle and speed meet SOLAS (full 35 deg, and 35 to 30 deg in 28 s at service speed; and equivalent for the auxiliary steering).
3. Check the continuous/ manual control: verify both the main (telemotor/ electric control) and the emergency/ auxiliary control are able to operate the live unit.
4. Power supply test: Trip one power feeder (or remove one motor circuit) and verify the other unit remains energised and operates; confirm the automatic reconnection/ alternative source.
5. Alarm test: Confirm that failure of one side raises audible/visual alarms on the bridge and in the engine room/ steering flat.
6. Pressure and leak test: Run the emergency/main pump at load and confirm pressure build-up and no leakage at seals/rams/valves on the affected circuit.
7. Redundancy verification: Confirm by the arrangement that a fault in one control system does not prevent the operation of the other unit (operation of the second control if the first fails).