Principles of naval engineering - Historic Naval Ships Association

Chapter 9-MACHINERY ARRANGEMENT AND PLANT LAYOUTThe reducing station that reduces steam from600 to 150 psig in the engineroom suppliessteam at 150 psig and 610° F to the main andauxiliary air ejectors, the distilling plant airejectors, and the turbine gland seal systems.Line desuperheaters are not installed in the150-psi system in the engineroom.In the No. 2 engineroom, a reducing stationreduces steam pressure from 150 psig to 100psig and supplies steam at 100 psig and 385° Fto the ship's laundry and tailor shop equipment.This 100-psi auxiliary steam system is calledthe 100-psi constant service system.The 150-psi system also supplies two50-psisystems— one a constant service system, one anintermittent service system. Both of these systemsare shown in figure 9-18.AUXILIARY EXHAUST SYSTEMSThe auxiliary exhaust system receives exhauststeam from pumps, forced draft blowers,and other auxiliaries which do not exhaust directlyto a condenser. Auxiliary exhaust steamis used in various units, including deaeratingfeed tanks, distilling plants, and (on many ships)turbine gland seal systems.The pressure in the auxiliary exhaust systemis maintained at about 15 psig. If the pressurebecomes too high, automatic unloading valves(dumping valves) allow the excess steam to goto the main or auxiliary condensers; in theevent of failure of these unloading valves, reliefvalves allow the steam to escape to atmosphere.If the pressure in the auxiliary exhaust systemdrops too low, makeup steam is supplied froman auxiliary steam system (usually the 150-psisystem) through augmenting valves.The auxiliary exhaust system must be clearlydistinguished from the various auxiliary steamsystems. Even though the auxiliary exhaustsystem is a steam system, it is not consideredan auxiliary steam system. A reexamination offigure 9-1 may be helpful at this point to clarify#2 ENGINEROOM #2 FIREROOM #1 ENGINEROOM #1 FIREROOMFigure 9-14.— Main steam system, DD 445 and DD 692 classes.ODECK OPERATED VALVE147.76211