Page 42 - Introduction to Marine Engineering

Diesel engines 29
Lubrication

The lubrication system of an engine provides a supply of lubricating oil
to the various moving parts in the engine. Its main function is to enable
the formation of a film of oil between the moving parts, which reduces
friction and wear. The lubricating oil is also used as a cleaner and in
some engines as a coolant.

Lubricating oil system
Lubricating oil for an engine is stored in the bottom of the crankcase,
known as the sump, or in a drain tank located beneath the engine
(Figure 2.17). The oil is drawn from this tank through a strainer, one of
a pair of pumps, into one of a pair of fine filters. It is then passed
through a cooler before entering the engine and being distributed to the
various branch pipes. The branch pipe for a particular cylinder may
feed the main bearing, for instance. Some of this oil will pass along a
drilled passage in the crankshaft to the bottom end bearing and then up
a drilled passage in the connecting rod to the gudgeon pin or crosshead
bearing. An alarm at the end of the distribution pipe ensures that
adequate pressure is maintained by the pump. Pumps and fine filters are

Cylinder
lubricating
oil service tank

Sea water

L Cylinder P*" t»
J lubrication o
box o
o
> •* ' **
1 \ manifold Sea water
Engine out

Strainer
Figure 2.17 Lubricating oil system