Page 63 - Introduction to Marine Engineering

50 Diesel engines

Exhaust gas from the engine is passed into a constant-pressure
receiver and then into the turbochargers. Scavenging is uniflow, and
electrically driven auxiliary blowers are automatically started during
low-load operation.
Lubricating oil is supplied to the various bearings and also to the
pistons for cooling. Cylinder oil is supplied via lubricators from a
high-level service tank. A separate lubrication system is provided for the
camshaft bearings to prevent contamination of the main lubricating oil
system. Fresh water cooling is provided for the cylinder jackets, cylinder
covers and exhaust valves.
The engine is designed to run on diesel oil or heavy fuel oil. An
electronic governor is provided as standard.

Piel stick

The Pielstick PC series engines are single-acting, medium-speed,
four-stroke reversible types. Both in-line and V-configurations are
available. The running gear, being a trunk-type engine, is made up of
the piston and the connecting rod which joins the single-throw
crankshaft. The arrangement of a PC4 engine is shown in Figure 2.30.
The crankcase and frame are constructed from heavy plate and steel
castings to produce a low-weight rigid structure. The crankshaft is
underslung and this arrangement confines all stresses to the frame
structure. The crankshaft is a one-piece forging and the connecting rods
are H-section steel stampings. The one-piece cylinder head contains two
exhaust and two inlet valves together with a starting air valve, a relief
valve, indicator cock and a centrally positioned fuel injector.
Exhaust-gas-driven turbo-chargers operating on the pulse system
supply pressurised air to the engine cylinders.
Bearing lubrication and piston cooling are supplied from a common
system. The engine has a dry sump with oil suction being taken from a
separate tank.
The cylinder jackets are water-cooled together with the cylinder heads
and the exhaust valve cages. The charge air cooler may be fresh-water or
sea-water cooled as required.
Fuel injection uses the jerk pump system, and a Woodward-type
hydraulic governor is used to control engine speed.
Later versions of the PC series engine are described as PC20 and PC40
and have somewhat increased scantlings.

Operating procedures

Medium- and slow-speed diesel engines will follow a fairly similar
procedure for starting and manoeuvring. Where reversing gearboxes or