Marine Engineering Study Materials

Ship’s main engine not maintaining service speed as required by the company. Assuming that the hull is still clean, the following areas would be investigated:

1. The power developed by the engine would be measured using power cards. This should conform to that expected at the normal service speed, referring to the power/speed relationship that has been shown over voyages when the service speed was normal.
2. The fuel consumption of the engine would be measured over an extended period of four, eight and twelve hours. This would be converted to specific fuel consumption in g/kWh identify if the engine is efficiently converting the fuel input.
3. A number of fuel injectors would be removed to ensure they are correctly operating by testing them.
4. For a slow speed engine, a scavenge inspection would be carried out to ensure the piston rings are still functioning as expected, and that the scavenge ports are clear and free from carbon residue.
5. The range of engine operating parameters would be measured, and compared to normal operating conditions. This would attempt to identify any system problems, such as air cooler fouling, turbocharger revolution change, etc.
6. The fuel presently being burnt would be analysed to identify if there are any high contaminants levels that could affect engine performance.
7. The slip of the vessel through the water would be calculated from engine revolutions, and actual vessel speed from the GPS system. This could indicate if the propeller is fouled as this problem would cause high propeller slip.

The following remedies would be carried out should a defect be identified:

1. If the fuel injectors were found to be defective, then all injectors would be removed and tested. Injector nozzles would be changed, and all internal components inspected by wear, and changed if suspect.
2. Any broken and severely worn piston rings would be changed. The liners would be calibrated during the piston overhaul, and changed if worn  0.5% of the nominal bore.
3. Any coolers that exhibit higher than normal differential pressures would be cleaned.
4. If the turbochargers were operating at a different speed that indicated by the power developed, then these would be dismantled and cleaned, with special attention on the nozzle ring and diffuser condition.
5. If the propeller slip exceeds 10% then the propeller would be inspected and cleaned at the first opportunity.