Question

The taking of bunkers is an important aspect of a Senior Engineer's responsibility.

(a) State the safe precautions that should be observed when bunkering

(b) Explain the importance of taking samples when bunkering.

(c) Explain a preferred method of taking samples.

(d) State the effect of EACH of the following in a fuel oil:

(i) High density.

(ii) High pour point.

(iii) High water content

Answer 1

Part (a)

Safety precautions that should be observed during bunkering:

All responsible officers should be familiar with all aspects of bunkering and the ship's bunkering system, and one such officer should personally supervise the operation.
He must be in close contact with the shore/barge, especially concerning stopping bunkers, in case of emergencies.
On arrival at the bunker port, delivery documents of the fuel supplier are to be examined and compared with the instruction of the owner/charterer.
Density, viscosity, sulphur content etc. are to be matched with the ordered ones.
All valves should be checked and those not to be used must be securely closed.
Oil-absorbent materials should be easily available.
Fire-fighting appliances to be kept handy.
Scuppers should be sealed.
The communication system should be checked between the ship and the shore. All hose connections are to be frequently checked.
Before bunkering sounding of the ullage at shore installation or barge is to be taken and signed jointly.
Ships tank soundings are to be taken.
The overflow tank should be kept empty for oil.
Trays must be fitted under joints.
Bunkering should start at a minimum rate so that any problem may be detected early.
Tanks should not be filled at more than 90% capacity, for the last two tanks final topping up should be done by gravity, if practicable otherwise pumping rate should be reduced.
On completion, special care should be taken when disconnecting hoses and removing drip trays.

Part (b)

Representative samples must be collected in bottles, sealed, signed & dated by both the Chief Engineer and the local supplier. Normally four bottles are collected. One for the ship, one for shore-based lab analysis, one for the supplier and one for MARPOL. In the event of a genuine quality/quantity problem arising, the supplier must be advised as soon as possible. The Supplier may decline to accept liability, if this is not done within a specified period. (The period of notification should be mentioned in the supplier's terms and conditions). In case of any problem regarding quality or quantity, a Letter of Protest is to be issued by the Chief Engineer. The sample must be representative of the total delivery, and ideally taken by drip feed at the discharge side of the manifold, during the course of the pumping process. Samples should not be taken at the start or on the completion of bunkering because then they will not be representative of the total tonnage loaded. Also, samples should not be from just one tank on the barge'

Part (c)

Fuel oil sampling procedure: When bunkering starts, place a container under the sampler, open the sampler valve fully and flush the sampler with fuel. It is good practice to check this Sample from fuel initially pumped on board as it may be high in water content from the bunker barge's tanks. After flushing, the sampler, close the valve and attach a suitable clean container to the valve. Adjust the needle valve to give a slow and steady drip. Time the fill rate so that it will provide for a sufficient estimated sample over the expected delivery period.

If the sample container fills during the bunkering period, remove it and place an empty sample container (Cubitainer) on the sampler and continue to draw a sample. On completion of bunkering, mix the samples from both containers to ensure a good, representative sample from the bunkering operation. Always ensure that the sampler valve is fully open to allow the sampler to drain. Always close the sampler valve before blowing through the fuel lines on completion of bunkering. Close the sampler valve if pumping stops, to prevent the sample from being drawn back, under vacuum, into the fuel line. Select three or four clean sample bottles. The exact number depends on the final destination of the various samples. It is recommended that four representative samples be obtained from the delivery.

The full Cubitainer should be placed in the pourer box and thoroughly shaken to ensure that the contents are mixed. Attach the pourer spout and gradually transfer the contents into the sample bottles, filling each a little at a time. If more than one Cubitainer was used during bunkering, then transfer a portion into each of the bottles. Complete the document labels and attach one to each sample bottle. Always have the barge operator to witness the removal and sealing of the sample bottle(s) (shown below). If this request is refused, or if no witness is provided, note this in the delivery log.

Bunker collection, sampling, and storage guidelines are provided in Annex VI of MARPOL 73/78 and have been defined by MEPC 96(47), which states that: "A retained sample of all fuel oils as supplied is drawn at the ships receiving manifold, sealed, signed on behalf of the supplier and the Master or ships officer in charge of the bunkering operation. Retained Sample is to be kept under ship's control until the subject fuel has been substantially consumed, but in any case for at least 12 months from the date of delivery."

It is important to remember that this Sample is to be used solely to determine compliance with Annex VI of MARPOL 73/78 and cannot be used for commercial purposes. However, samples can be drawn at the same time for other purposes.

Part (d)

(i) Effect of High Density: Density is defined as the mass per unit volume and expressed in Kg/m3 in Sl units. Marine Fuel oils have a linear density/temp. relationship, as opposed to water for example, and decreases with increasing temperature at a rate of about 0.66 Kg/m3 per degree C rise.

Quantity calculation
Separability of water & solids - to select the optimum size of gravity disc for purification.
Specific energy calculation.
Calculated Carbon Aromaticity Index (CCAI) measures the ignition quality (an increased index does not cause an increase in ignition delay).

(ii) Effect of High pour point:

Wax formation impeding fluidity.
The pour point is the lowest temperature at which marine fuel oil can be handled without excessive amounts of Wax Crystals forming out of the solution.
At 30C, below the pour point temperature, the fuel will become gel thereby preventing flow under its weight. So more viscous fuels are required to be heated to maintain their pumpability.

(iii) Effect of High water content:

Wet sludge
Corrosion (especially seawater)
Possible ignition interference.
Displacement of fuel quantity.
Specific energy calculation (heat loss).

Saline Water in the emulsified state has a particular affinity for highly cracked fuels and heavy sludging can be experienced during purification. Water can cause cavitation in pump suction, and corrosion, and while in combustion space, atomization can be disturbed, ignition retarded and the cylinder lubricant film diluted. Water is normally removed by gravitational separation in the fuel tanks and by the centrifuge purification system

✓ Verified Model Answer (Text Solution)

Safety precautions that should be observed during bunkering:

(i) Effect of High Density: Density is defined as the mass per unit volume and expressed in Kg/m3 in Sl units. Marine Fuel oils have a linear density/temp. relationship, as opposed to water for example, and decreases with increasing temperature at a rate of about 0.66 Kg/m3 per degree C rise.