Optimising reliability

In ensuring optimum lifetime reliability of a medium-speed diesel engine the user must be aware of certain key factors, not least the importance of the supplier/user relationship .

To achieve an acceptable level of reliability throughout the lifetime of a typical medium-speed engine, a satisfactory exchange of information between the supplier and the user, and adequate support from the supplier is most important.

The supplier, of course, is responsible for providing an engine which has been thoroughly tested and is designed to incorporate proven features that provide satisfactory:

l Oil film thicknesses, piston speeds and lube oil filtration standards.

l Critical engine component stresses, particularly connecting rods. Pistons, gudgeon pins, bearings, crank and camshafts.

l Engine operating temperatures, particularly the components subjected to high thermal, fatigue, load cycling conditions.

l Turbocharger/Intercooler matching throughout the engine load range and also acceptable load acceptance performance.

l Fuel injection equipment.

The engine supplier will set the release rating of his engine with both the sales and reliability prospects in mind. It is the user?s responsibility, however, to ensure that their engine will be operated within these ratings. This will be influenced by the grade of fuel, the ambient conditions and preferably an 85% continuous load factor or below.

To ensure that the engine achieves its optimum reliability performance, the user will need to be aware of the manufacturer?s engine maintenance recommendations, the engine overhaul intervals and the expected component life factors.

The recommended maintenance programmes designed to achieve an ideal engine reliability performance include the following:

l Operate an approved maintenance programme

This should comply with the supplier?s overhaul intervals and component recommendations, as well as fuels grade and load factors.

l Regular sampling and analysis of fuel, lubricating oil and water

Basic compliance with the analysis recommendations and the entry of results in a dedicated logbook.

l Maintenance/operating log entries

It is highly recommended that a detailed dedicated logbook concerning all the maintenance activities carried out on each engine be kept current. This includes all planned and unplanned activities, as this is of extreme importance in the event of recurring engine problems.

l Fuel and lubricating oil treatment

It is vital that both the fuel and lubricating oil cleaning/treatment equipment is maintained at its optimum performance capability. This particularly applies to fuel rail viscometers, ring main heaters and temperature control equipment. Also, filter pressure differentials and particle size measurement equipment and the condition of the respective purifier and separation equipment.

The monitoring of the fuel quality received on board is especially important as the use of a fuel that is outside of the engine supplier?s maximum limits can have a very serious and detrimental effect on the satisfactory performance and wear rates of an engine.

l Turbochargers and charge air coolers/heaters

When engines are operated with ambient air temperatures below 5°C it is important that the ?no load? charge air heaters are operated to prevent the possibility of cylinder detonation when full fuel is suddenly applied. It is also important that the engine jacket water is maintained at approximately 38 to 40°C if quick engine load acceptance is a requirement.

l Engine tune/adjustments

The engine fuel consumption cylinder peak, compression pressures, fuel timing and fuel start limiters should be regularly checked and adjusted as required.

The importance of maintaining an effective working relationship between an engine supplier and user cannot be stressed enough. If necessary, the services of an independent engine specialist engineer can also help ensure that an engine achieves its expected through-life performance.

It is important to bear in mind that the use of non-original engine spare parts can result in premature engine operation problems, in particular with such components as pistons, liners, main and bottom end bearings, cylinder heads and valves.

That the acceptance of a well-engineered, high-specification engine should continue to find favour with many engine users providing that a particular engine can achieve a satisfactory through-life reliability/availability performance.