It is the same cross reverse flow flushing system like the smaller type 6.46. The drive was changed into an electric motor because a higher force to rotate the flushing device is needed. Safety for these big engines requires a safety filter basket downstream the filter element or an even more valuable single indicator filter of 80 micron downstream the automatic filter.
An automatic filter with bypass filter is another possible solutlon but it only gives the same protection if the bypass filter is sized large enough. It should have the same filtration degree as the automatic filter. Most of the recommendations of the engine manufactures have only one automatic filter without bypass.
In addition to the main lube oil flow the lubrication for the turbo charger bearings must get filtered with 30 micron. This is done by a continuous backflushing filter 6.46.
A new option which has been installed is the 6.61 backflushing filter (upgraded version) which can filter down to 34 micron and finer. This is acceptable for the turbo charger oil as well as for the main lube oil flow.
A recent development with a 2-stroke engine manufacturer offers a very cost-saving solution for the replacement of the hydraulic tank and oil system by just using an automatic filter.
The target for this development was to reach a cleanness level according to ISO 4406 of 16 / 13 by filtration. For particles larger than 15 micron the requirements were met, but equally important for the wear of the hydraulic components are the sizes between 5 and 15 micron. The 10 micron mesh which was tested first was not able to keep the number of particles within the ISO Ievel. The 6 micron candles were able to meet this demand. Besides this fine filtration for the hydraulic components the filter will keep the total particle amount of the system oil at a low level. The fiushing oil of the automatic filter flows to the suction side of the separator which is always installed on ships with large two-stroke engines. This very clean oil may be used for other parts that have to be lubricated with very clean oil.
Conclusion
To use automatic filters in combination with centrifugal filters is the prospective for lube oil systems of smaller high and medium speed diesel engines. The integration of engine parts into the filter casing is the cost-saving trend which improves the protection for the engine. Wire mesh and fabric with solid retention rates comparable to a paper filter has been tested successfully. Engine manufacturers who have gained experience with this system are WNSD, MAK, MTU, MAN, Deutz MWM. SKL.
Two-stroke engines will get a finer filtration: 34 micron instead of 50 micron. With an implemented micron filter in the bypass. The total cleanness level will improve and costs for a separate oil system can be saved.
