1.2 Circulating water systems
?In motorships there are two main circuits,one salt,one
fresh,
?The salt circuit is,sea inlet box (seachest) - pump(s) -
f.w,coolers in series (first LT then HT) – turbo blower
aftercoolers in parallel (if any) – provision condenser in
parallel (if any) - overboard.
?Branches (Not be shown in Fig.) may be taken to blower
oil coolers,fuel valve cooling oil coolers and from the
outlet side,to evaporator sea inlets or domestic warm
water systems,baths,etc.
?There may be a blanked connection to the fresh water
circuit.
1.2 Circulating water systems
?The fresh water circuit being under positive head,
is closed,i.e,pump-fresh water coolers - cylinder
jackets - cylinder heads - exhaust valves (if any)
– turbo – blowers (if any),- pump inlet,
?There may be closed circuit branch to evaporator
primary-stage heating inlets,
?If the engine pistons are water-cooled,the circuit
may be in parallel with the jacket circuit; it is
more likely to be separate,the circuit being,
pump – cooler - inlet manifold- telescopic tubes-
outlet manifold- pump,
1.2 Circulating water systems
?The f.w,temperature
should be kept as high
as practicable by the
use of the salt water
bypass valves on oil
and f.w,coolers,
?These may be butterfly
valves controlled by
thermo-pneumatic
devices,
1.2 Circulating water systems
?It is usual to provide for
warming the fresh
circulating water before the
main engines are started,
either by steam or more
usually,by bleeding from the
auxiliary fresh cooling
circuit.
1.2 Circulating water systems
?The air compressor inter-and after- coolers are likely
to be supplied in parallel;
?It is unusual for supercharger blowers to have
aftercoolers; if they have,they will be circulated
similarly,
?The auxiliary fresh water system is similar to the main
and may use the same header tank if the resulting
head is not too great; if it is,a separate header tank
will be provided.
1.2 Circulating water systems
?If the pumps for each service are not duplicated,they will
be dual-connected,
?If one pump fails,the survivor becomes the fresh water
pump and a clean service e.g,ballast pump circulates the
sea water.