IAMI Question Help needed

[Jimmy Jazz]

Hello, two questions needing help on

1) state the reason for leaving lubricating oil circulating after "finished with engines" ?

2) state why diesel alternator cooling water may be circulated through the main engine after shut down?

many thanks

[chris]

well I'm pretty sure I know these answers and I'm not even an engine cadet.

Have you got the Reeds range of books to hand?

[glider23]

1) if by "finished" you mean stopped that probably because to slowly cool and preserve the engine, 2) I guess for the same reason to slowly cool it

[Clanky]

Lub oil is circulated after the engine is stopped as the engine components can contain residual heat which if not gradually and evenly cooled would cause thermal stresses. It is important that any long term circulation is done with a low pressure priming pump rather than a stand-by lub oil pump designed to give full flow / pressure when the engine is running as this can cause erosion in a stationary engine.

Cooling water is circulated for the same reason, but it can also be used to keep the engine warm either by use of electrical pre-heaters which heat the water or by diverting cooling water from other engines. Engines started from cold will be subject to uneven thermal stresses and low temperature corrosion, so pre-heating is a very important part of maintaining the engine in good working condition.