THE FORGOTTEN PARTS OF MAIN ENGINEWe would like to bring to your kind attention an issue which may cause undesired incidents onyour main engine.You may aware service letter SL2008-492 and relevant alerts from Swedish Club but afterpersonally witnessing same situation, we decided to share this experience with you and remindthe importance of the issue.While we were opening main engine bearings for class inspection during vessel in drydock,everything seems good such as appearance oil, cleanliness of crankcase etc.Upon completing of job, we left vessel and come back a few days after launching. Once we opencrankcase door for deflection measurement, (which vessel already started lub oil pump before ourarrival) we have observed that lubrication oil deteriorated from excessive water in the lubricationoil system, which result replacing whole lubrication oil in the system.After further investigation, we found out reason as extreme water presence on tank top (betweenmain engine and sump tank) and teared diaphragm membrane. Since vessel at drydock and crewbusy for hectic jobs, ignored bilge alarm raised from M/E sunken part and could not realise wateraccumulation below main engine.Why this part became forgotted?1. Because of design, even if membrane or bellow damaged, not possible to understandwithout dismantling. (Oil never leak to tank top)2. In order to water leak to sump tank, water level to increase minimum 10-15 cm,but normallybilge alarm raising before that level and ship crew keeping tank top area at dry condition. Onlydrydocking period, it is easy to disregard bilge alarm and water accumulation on the tank top area.How To Prevent Incident?1. Best way to follow service letter and inspect/replace the defective parts.2. Emphasize the importance to keep tank top dry and pay special attention to alarm raisedfrom M/E sunken area, especially during drydock period.
Service letter SL08-492/JVGMarch 2008Rubber Diaphragm Sealings in Crankcase Oil OutletsAction Code: WHEN CONVENIENTThe crankcase lubricating oil outlets guide the lubricating oil from the crankcase to thebottom tank. A diaphragm at the outlet pipes prevents water and other liquids in thearea from contaminating the main engine lubricating oil system, which could lead tofatal damage of the main engine bearings.According to our Checking and Maintenance Schedule in the instruction manual ofMAN B&W engines, we recommend to check the condition of the diaphragm in thecrankcase oil outlet every 32,000 hours of operation and to replace the diaphragm ifnecessary. The procedure concerns rubber diaphragms as well as metal bellowdiaphragms. However, due to the risk of material problems in rubber diaphragms, werecommend to replace the rubber diaphragms at every scheduled inspection, which isnoted in our checking procedure (no. 912-5.1) for Crankcase Oil Outlet, enclosed withthis letter. It should be noted that the membranes are normally supplied by theshipyard and not by the engine manufacturer.We draw your attention to the above-mentioned schedule and our procedure andinform you as follows:How to avoid defect rubber diaphragmTo avoid water entering the main engine sump tank through a defect crankcase oiloutlet, it is recommended to:Inspect the diaphragm sealing in the crankcase oil outlet every 32,000 hours ofoperation and replace the diaphragm if necessary. Always replace rubber