Slow Speed Diesel Engines are the power houses of the marine industry
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Slow speed diesel engines are typically used as the main propulsion unit for merchant ships.
They are very efficient and are able to burn residual fuel oil grades. However these benefits also impose some lubricant related problems.
Cylinder Oil
Cylinder oil - this is a high BN, high viscosity oil that is injected into the cylinder liners through one or sometimes two rings of injectors. The oil serves three roles; lubricating the liner, neutralizing acids from combustion and removing debris from the rings and liner surface to drain via the scavenge space. The oil is used once only and not recovered.
Recently introduced legislation, IMO MARPOL 73/78 Annex VI and EU Directives will control the sulphur content of marine fuel used in sensitive areas known as SECA – Sulphur Emission Control Area's. This places some interesting demands on the cylinder oil, in that there may be a necessity to change the BN of the oil to better match the fuel sulphur content. The Kittiwake TBN test is used for this purpose.
Additionally, there is a move to reduce the feed rate of cylinder oil resulting in significant savings in operating costs. The problem is that it is difficult to predict just what the minimum should be, as it changes with sea state, power, fuel, cylinder number etc.
Kittiwake have two innovative solutions for this:
Off-line analysis of the scavenge drains for BN and Iron content - We manufacture both of the analysers currently used for this purpose.
On-line analysis of the scavenge drains - This is a new development using the ANALEXrs series of analysers and is currently under trial on large container ships.
Crankcase Oil
System oil is used in the crank space of these engines. It is a low BN oil with a primary purpose of lubrication, as it does not contact the combustion spaces. The system is filtered and centrifuged, subject to periodic top-up and if treated carefully, will last indefinitely.
Water is a major contaminant and is easily identified through testing. Base Number (BN) can also rise, which is an indication of leaks around the piston gland, as is a build up of insolubles. Again, both are easy to test for. Viscosity only really changes if the engine is topped up with the wrong oil grade.
See also the Directory of Bearing Failures for further information on potential damage to diesel engines.
Oil Testing for Slow Speed Diesel Engines
There are numerous oil testing solutions available for slow speed diesel engines, including:
Want to know more?
ContactKittiwake here