The system oil is stored at the bottom of the crankcase or in a drain tank located under the engine. The oil is extracted from this tank through a strainer, a pump and a fine filter. It is then passed through a cooler before entering the engine and distributed to the various bypass pipes.
The branch pipe of a particular cylinder can feed the main bearing, for example. Part of this oil will pass through a drilled hole in the crankshaft to the lower end bearing, and then climb through a drilled hole in the connecting rod to gudgeon pin or crosshead bearing.
After use in the engine, the lubricating oil is discharged to the sump or the drain tank for reuse. A centrifuge is designed to clean the lubricating oil in the system and a clean oil can be supplied from a storage tank.