Marine Engineering Study Materials

Auxiliary Engine Performance

In order to monitor the engine performance, we would need to measure the power output and fuel consumption of the engine. This will allow the performance of the engine to be measured against previous and even test bed readings.

1. For monitoring auxiliary engine performance, peak pressure of each unit is taken at 85% engine load. All the engine parameters such as exhaust temperatures, fuel rack readings, fuel oil, lube oil and cooling water pressure, temperatures, scavenge air pressure, turbocharger speed, etc. are taken. Compare the readings with previous and test bed reports, compare the peak pressures of all units to ensure even loading of all cylinders. These measurements would be taken every month.
2. Measure the power of the each cylinder by electronic pressure measurement, if available. If the engine was driving an electrical load, then the electrical output power could be used. This will allow the total engine power to be calculated, and also for any power imbalance to be detected. This power measurement would be taken every month.
3. Measure the fuel consumption of the engine every day over a 8 and 24 hour period. This consumption would be measured in tonne/hour, and thermal and density conversions from a volumetric flow rate at the meter would be required.
4. Calculate the specific fuel consumption of the engine in terms of g/kWh, so that fuel consumption at various engine conditions could be compared.

Lube oil system can be treated as blood circulation for an engine. Closely monitor the pressure differential across the lube oil filters each day, and to report any increase in this pressure, or the frequency of automatic filter blowdown.

1. Take a representative sample from the lube oil inlet to the engine every week.
2. This sample would be tested on board for
   water content, change in viscosity, TBN reserve, sludge accumulation, etc.
3. In addition every month a representative sample would be taken and sent for shore analysis so that a wider range of variables could be analysed.

The general condition of the engine could be monitored by measuring the various parameters taken by the data logger or manual log readings.

Take a full set of readings twice a day on all the major parameters of the engine, such as Exhaust gas temperatures, Lube oil pressure and temperature, Fresh water cooling pressure and temperature, Scavenge air pressure and temperature, T/C rev/min, Exhaust gas smoke levels

These readings would form the basis of the datum readings for that engine, and any major changes to the measurements should be reported to the Chief Engineer without delay.

Condition Monitoring and Planned Maintenance

Various readings taken from running engine, such as pressures and temperatures. These are easily obtained, and can be used to indicate changes in operating conditions when compared to previous stable readings. The readings need to be taken over an extended period of time to avoid rouge readings producing incorrect analysis. Engine builders software programs are available that can analysis such data to indicate the condition of the engine.

As mentioned earlier, engine performance data can provide useful information about the various pressures of combustion and compression which can give a picture of degradation and condition of combustion inside the engine.

Previous maintenance measurements will give an estimate of when maintenance is required, by applying anticipated wear rate levels to the wear already experienced.

Planned maintenance is based on the idea that wear and fouling will take place at a constant or uniform level, and as such regular time based maintenance will correctly ensure the engine operation at all times. However PM based maintenance does not account for changes in environmental or operating conditions. Hence the engine could be overhauled too early or too late using running hours alone.

Also measuring engine parameters is only partly successful in determining engine condition. They often can not monitor slight changes in engine operation, such as fall off in fuel injector performance, even though this can lead to increased fouling etc. Thus condition monitoring should predict major changes, but regular cleaning of turbochargers and piston rings still require PM schemes that are usually based on time and/or hours.