Steam - Supply and Return Overview.
Ships boilers operate at high pressure and temperatures, often supplying superheated steam to the main engines. Therefore the steam pressure has to be decreased and this is achieved by passing it through a number of pressure reducing valves and de- superheating if required. The de-superheater is a pressure vessel where condensate is sprayed into the superheated steam flowing through it, converting the superheated steam to saturated steam. The de-superheater is located in the ships boiler room.
When steam is required on deck; the drains on the steam driven components and supply piping on deck are opened and all steam traps checked to be operating correctly. Only then is the steam to deck isolating valve in the engineroom very slowly opened. This is particularly important after the system has been shut down during a long sea voyage and will prevent damage to the pipes and flange gaskets due to rapid thermal expansion and water hammer.
Steam is supplied to the galley for cooking and hot water and also supplied to and a heat exchanger for the accommodation.
A steam hot water calorifier in the engine room provides domestic hot water to the accommodation.
The steam from these components and functions is returned through piping back the engineroom auxiliary steam condenser. This is cooled by seawater and the resultant condensate returned to the boiler feed system.
This condensate from the auxiliary condenser is regularly tested for oxygen and acids content, and an on-line salinometer is normally fitted which dumps the condensate if the salt ppm is too high. These feedwater contaminates would corrode the insides of the boiler water tubes if allowed to enter the boiler water system. A sketch of an auxiliary condenser is shown below.