Brief introduction to marine engine cooling system

Engine cooling system is crucial to the normal operation of a diesel engine,especially for the marine application.The basic working principle works for both marine engines and on-land engines.So,that is to say,no matter what type of diesel engines or where you will want the engine to operate,it’s worth reading this article.

There are two types of engine cooling systems,the raw water system and the enclosed cooling system,and the enclosed cooling system is commonly found in large engines.Of all the marine diesel engines,enclosed water cooling system is employed on every ship.

What is raw water cooling system for an diesel engine?

As the words suggests,engines are cooled by the raw water,which is used without any treatment.For on-land situations that could be reasonable since fresh water is everywhere.And the fresh water is harmless to the engine parts.Raw water is drawn in and flow through the internal channel of the diesel engine and then be discharged outside.But for a ship/Drilling platform that would be impossible cause you possess not enough fresh water on the sea,enclosed cooling water system is therefore be applied to this circumstances.

What is enclosed water cooling water system for a marine diesel engine?

Fresh water is circulating around the fresh water part of the cooling system without being discharged,they will be cooled by a device called heat exchanger,that is commonly found on ships.After the fresh water has been cooled to the normal level they will continue to cool the engine.What material will be used to cool the fresh water?Normally,two kinds of mediums will serve this purpose.

1.Air cooled system

There will be a air cooling system,not directly for the engine,is used to cool the fresh water.Very big fan and coiler,fresh water flow through the coiler and the air is forced to cool the water.This air cooling system is not used too much because of the poor efficiency as compared to the sea water cooling system.But for a jack up rig this is not that bad since when the jack up has been jacked up,do you expect it to pump up water through the sea chest?Then there is no way to cool the fresh water,the only way to do it is using the air cooled system,if not,you will otherwise need to purchase extra submerged pump to draw the sea water in the sky!
2.Sea water cooling system

Warmed fresh water is cooled down inside heat exchanger where the cold sea water is warmed up,you can have as much as sea water you want on a sea,sea water is drawn in through a gate called sea chest,through which the debris and fish can be filtered out,preventing the heat exchanger from clogging.

For both of the two kind of marine engine cooling systems,a thermostatic valve is the key component,as the temperature of the inlet cooling water is configured to a certain value,the thermostatic valve is functioning as a temperature regulator where the high temperature cooling water and the feed cooling water can be mixed to the default value,then finally be drawn into the engine to cool the engine parts.

For marine application,both the fresh water cooling system and the sea water cooling system will need to be equipped with extra centrifugal pumps to provide the system with sufficient pump head,especially for the semi-submersible vessels,where th diesel engines are installed on a level of more than 30 meters high,the engine drived cooling pump is not expected to draw water inside from such a height.

Marine engine cooling system is a little bit complex than the normal diesel engine,and the main idea of cooling the engine is to use fresh water to cool the engine parts,and then to use whatever you want to cool the fresh water.That is how a marine diesel engine cooling system works.