The condition of a diesel engine can be assessed using various machinery condition monitoring (MCM) techniques. These methods help determine the actual condition of machinery and indicate when maintenance is truly necessary, rather than relying only on fixed overhaul intervals. By continuously collecting and analysing operational data, potential problems can be predicted or diagnosed at an early stage.

The following methods are commonly used for condition monitoring:

1. Visual Inspection

Regular visual examination of engine components and surrounding systems is one of the simplest and most important methods of monitoring condition.

Observations may include:

• Oil leaks
• Fuel leaks
• Abnormal smoke
• Excessive vibration
• Unusual noise
• Overheating signs
• Loose connections or fastenings

Careful recording of observations helps identify gradual deterioration over time.

2. Trend Analysis of Engine Performance

Engine operating parameters are continuously monitored and compared over time using computer-based systems.

Parameters commonly monitored include:

• Exhaust gas temperatures
• Scavenge air pressure
• Fuel consumption
• Lubricating oil pressure and temperature
• Cylinder pressures
• Turbocharger speed

Any abnormal trend or deviation from normal values may indicate developing faults or wear.

3. Vibration Analysis

Vibration measurements are taken using fixed sensors or portable instruments.

The readings are analysed through specialized computer software to detect:

• Bearing wear
• Shaft misalignment
• Imbalance
• Mechanical looseness
• Gear or coupling defects

Changes in vibration patterns often provide early warning of machinery problems.

4. Lubricating Oil Analysis

Regular sampling and laboratory analysis of lubricating oil provide valuable information about engine condition.

Oil analysis can detect:

• Metal particles from wear
• Water contamination
• Fuel dilution
• Oxidation and degradation of oil
• Presence of abnormal contaminants

Detailed shore-based reports help identify component wear before serious damage occurs.

5. Thermal Imaging

Thermal imaging cameras are used to monitor and record equipment temperatures.

This method helps identify:

• Hot spots
• Overheating bearings
• Electrical faults
• Insulation failures
• Uneven temperature distribution

Abnormal temperature patterns can indicate developing defects.

6. Periodic Measurements and Calibration

Regular measurement and calibration of components help detect wear and loss of accuracy.

This may include:

• Wear measurements
• Clearances and alignment checks
• Calibration of instruments and sensors
• Laser alignment checks for shafts and couplings

Changes in alignment or dimensions may indicate fatigue, wear, or impending failure.

Machinery Condition Monitoring (MCM)

Machinery Condition Monitoring is a maintenance approach that recommends maintenance actions based on the actual condition of equipment. By analysing collected data and observing trends, maintenance can be planned before major failures occur, improving reliability and reducing unnecessary overhauls.

Condition Monitoring and Planned Maintenance Schemes are both important maintenance strategies, but they differ in approach and application.

Planned Maintenance Scheme (PMS)

Under PMS:

• Maintenance is carried out at fixed intervals based on:
  • Running hours
  • Calendar time
  • Manufacturer’s recommendations
• Components are overhauled whether deterioration exists or not.
• It ensures regular inspection and compliance with maintenance schedules.

Advantages

• Simple to organize and plan
• Helps ensure statutory and class compliance
• Reduces risk of missed maintenance

Limitations

• Components may be overhauled unnecessarily
• Useful service life of parts may not be fully utilized
• Increased spare part usage and labour cost
• Unexpected failures may still occur between intervals

Machinery Condition Monitoring (MCM)

Under MCM:

• Maintenance is based on the actual condition of machinery.
• Data collected through monitoring techniques is analysed to predict failures.
• Maintenance is performed only when indicators show deterioration or abnormal trends.

Advantages

• Reduces unnecessary overhauls
• Minimizes downtime
• Extends component life
• Improves reliability and operational efficiency
• Reduces maintenance cost and spare consumption

Relationship Between PMS and MCM

Machinery Condition Monitoring significantly enhances and optimizes Planned Maintenance Schemes.

• Many classification societies provide survey concessions to ships operating approved PMS and MCM systems.
• Certain survey requirements may be satisfied through monitoring records without complete dismantling of machinery.
• Survey intervals can sometimes be extended, reducing:
  • Operational downtime
  • Labour requirements
  • Spare part costs