Principles of naval engineering - Historic Naval Ships Association

Chapter 9-MACHINERY ARRANGEMENT AND PLANT LAYOUTand galley, as well as providing makeup waterfor various fresh water cooling systems.HYDRAULIC SYSTEMSHydraulic systems are used aboard ship tooperate steering gear, anchor windlasses, hydraulicpresses, remote control valves, andother units. 11 Hydraulic systems operate on theprinciple that, since liquids are noncompressible,force exerted at any point on an enclosedliquid is transmitted equally in all directions.Hence a hydraulic system permits the accomplishmentof a great amount of work with relativelylittle effort on the part of shipboardpersonnel.The medium used to transmit and distributeforces in hydraulic systems may be a petroleumbaseproduct (hydraulic oil) or a pure phosphateester fluid. Phosphate ester fluid is more resistantto fire and explosion than the petroleumbaseoil that was used in all hydraulic systemsuntil fairly recently. Phosphate ester fluid isnow used in aircraft carrier elevators, surfaceship missile systems, jet blast deflectors],seaplane servicing booms, high pressure sub(-marine systems, and all hydraulic systemsoperating at pressures of more than 500 psiin new construction and conversion surfaceships.METHODS OF PROPULSIONPLANT OPERATIONThe major engineering systems on mostnaval ships are provided with cross-connectionswhich allow the engineering plants to be operal^Manyhydraulically operated units are discussed inchapter 21 of this text.ted either independently (split-plant) or together(cross-connected). In cross- connected operation,boilers may supply steam to propulsionturbines which they do not serve when the plantis split. In split-plant operation, the boilers,turbines, pumps, blowers, and other machineryare so divided that there are two or moreseparate and complete engineering plants.Cross- connected operation was formerlystandard for peacetime steaming, and splitplantoperation was used only when maximumreliability was required— as, for example, whena ship was operating in enemy waters in timeof war, operating in heavy seas, maneuveringin restricted waters, or engaged in underwayfueling. However, the greater reliability ofsplit-plant operation has led to its increasinguse. At the present time, split-plant operationis the standard method of underway operationfor most naval ships; cross- connected operationis used for in- port steaming but is rarelyused for underway steaming.On some ships the engineering plants can beoperated by a method known as group operation.For example, the USS Forrestal. CVA 59, hasfour separate propulsion plants. The two forwardplants (No. 1 and No. 4) constitute theforward group and the two after plants (No. 2and No. 3) constitute the after group. Althougheach of these four plants is normally used forthe independent (split-plant) operation of oneshaft, the boilers in any one plant can be crossconnectedto supply steam to the turbines in theother plant in the same group. While underway,therefore, the boilers in the No. 1 plant can becross- connected to supply steam to the No. 4plant, although they cannot be cross- connectedto supply steam to the two plants in the othergroup. For in-port operation, any boiler can becross- connected to supply steam to any turbogeneratorand to all other steam-driven auxiliaries.229