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Cooling of ships engine - how it works , requirement of fresh water & sea water cooling system
Cooling of engines is achieved by circulating a cooling liquid around
internal passages within the engine. The cooling liquid is thus heated up
and is in turn cooled by a sea water circulated cooler. Without adequate
cooling certain parts of the engine which are exposed to very high
temperatures, as a result of burning fuel, would soon fail.
Cooling
enables the engine metals to retain their mechanical properties. The
usual coolant used is fresh water: sea water is not used directly as a
coolant because of its corrosive action. Lubricating oil is sometimes used
for piston cooling since leaks into the crankcase would not cause
problems. As a result of its lower specific heat however about twice the
quantity of oil compared to water would be required.
Fresh water cooling system
A water cooling system for a slow-speed diesel engine is shown in Figure
. It is divided into two separate systems: one for cooling the cylinder
jackets, cylinder heads and turbo-blowers; the other for piston cooling.
The cylinder jacket cooling water after leaving the engine passes to a
sea-water-circulated cooler and then into the jacket-water circulating
pumps. It is then pumped around the cylinder jackets, cylinder heads
and turbo-blowers. A header tank allows for expansion and water
make-up in the system. Vents are led from the engine to the header tank
for the release of air from the cooling water. A heater in the circuit
facilitates warming of the engine prior to starting by circulating hot
water.
The piston cooling system employs similar components, except that a
drain tank is used instead of a header tank and the vents are then led to
high points in the machinery space. A separate piston cooling system is
used to limit any contamination from piston cooling glands to the piston
cooling system only.
Sea water cooling system
The various cooling liquids which circulate the engine are themselves
cooled by sea water. The usual arrangement uses individual coolers for
lubricating oil, jacket water, and the piston cooling system, each cooler
being circulated by sea water. Some modern ships use what is known as a
'central cooling system' with only one large sea-water-circulated cooler.
This cools a supply of fresh water, which then circulates to the
other Individual coolers. With less equipment in contact with sea water
the corrosion problems are much reduced in this system.
A sea water cooling system is shown in Figure . From the sea
suction one of a pair of sea-water circulating pumps provides sea water
which circulates the lubricating oil cooler, the jacket water cooler and the
piston water cooler before discharging overboard. Another branch of
the sea water main provides sea water to directly cool the charge air (for
a direct-drive two-stroke diesel).
Central cooling system
In a central cooling system the sea water circuit is made up of high and low suctions, usually on
either side of the machinery space, suction strainers and several sea
water pumps. The sea water is circulated through the central coolers and
then discharged overboard.
A low-temperature and high-temperature
circuit exist in the fresh water system. The fresh water in the
high-temperature circuit circulates the main engine and may, if
required, be used as a heating medium for an evaporator. The
low-temperature circuit circulates the main engine air coolers, the
lubricating oil coolers and all other heat exchangers. A regulating valve
controls the mixing of water between the high-temperature and
low-temperature circuits. A temperature sensor provides a signal
Related Information:
Cooling system for running machinery on board
Countermeasures against scavange space fires
Four stroke cycle diesel engines operational guideline
Two stroke cycle diesel engines operational guideline
Four stroke cycle diesel engines operational guideline
The fuel oil system for a diesel engine
Function of fuel injector for a diesel engine
Lubricating oil system for a marine diesel engine - how it works
Two stroke cycle diesel engines operational guideline
Scavenging methods - Cross-flow scavenging, loop scavenging, & uniflow scavenging
Countermeasures against scavange space fires
Various Heat exchanger for running machinery on board cargo ships
Starting air system for diesel engine - how it works
Power measurement for marine diesel engine - The engine indicator
Sea water circulation of coolers for lubricating oil, piston cooling, jacket water, charge air, turbo-charger
The gearing arrangement to reduce engine drive down to suitable propeller revolutions
Control and safety devices for marine diesel engine - function of governors
MAN B&W diesel engine - Basic principles and operational guideline
How a sulzer engine works ? Sulzer RTA72U diesel engine -Operational guideline
Couplings, clutches and gearboxes of a marine diesel engine
Difference between two stroke and four stroke cycle diesel engines
Explosion relief valve of a marine diesel engine
Cylinder relief valve of a marine diesel engine -
operational guideline
Turning gear operational guideline
Crankcase oil mist detector of a marine diesel engine
Marine machineries - Useful tags
Marine diesel engines ||Steam generating plant ||Air conditioning system ||Compressed air ||Marine batteries ||Cargo refrigeration ||Centrifugal pump ||Various coolers ||Emergency power supply ||Exhaust gas heat exchangers ||Feed system ||Feed extraction pump ||
Flow measurement || Four stroke engines || Fuel injector || Fuel oil system || Fuel oil treatment ||Gearboxes || Governor ||
Marine incinerator ||
Lub oil filters ||
MAN B&W engine ||
Marine condensers ||
Oily water separator ||
Overspeed protection devices ||
Piston & piston rings ||
Crankshaft deflection ||
Marine pumps ||
Various refrigerants ||
Sewage treatment plant ||
Propellers ||
Power Plants
||
Starting air system ||
Steam turbines ||
Steering gear ||
Sulzer engine ||
Turbine gearing ||
Turbochargers ||
Two stroke engines ||
UMS operations ||
Drydocking & major repairs ||
Critical machinery ||
Deck machineries & cargo gears
|| Control and instrumentation
||Fire protection
||Engine room safety ||
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