Principles of naval engineering - Historic Naval Ships Association

PRINCIPLES OF NAVAL ENGINEERINGCONTMLVALVE,SfSta^iiiEXHAUSTSIGHT FLOWSFLEXIBLESIGHTCOUPLINGnow.CLEARANCE INDICATORTHRUST BEARING^ .FLEXIBLE COUPLINGWASTE OIL DRAINAFTER BEARING OIL DRAINCARBON PACKING VENT \ySEALING STEAM LEAKOFF FROM H.P. PACKING\SEAUH6 STEAMLEAK-OFFSTEAM FROM CRUISING TURBINEPACKINGVENTFigure 12-26.— High pressure turbine.96.10economy measures can-Aboard naval ships,not be carried to extremes, because there areseveral safety factors that must be considered.Unless proper safety precautions are taken,reliability may be sacrificed; and in the operationof naval ships, reliability is one of the moreimportant factors. In operating an engineeringplant as economically as possible, safety factorsand good engineering practice must not be overlooked.There are several factors that, if givenproper consideration, will promote efficient andeconomical operation of the engineering plant.Some of these factors are: (1) maintaining thedesigned steam pressure, (2) proper accelerationof the main engines, (3) maintaining highcondenser vacuum, (4) guarding against excessiverecirculation of condensate, (5) maintenanceof proper insulation and lagging, (6) keepingthe consumption of feed water and potable waterwithin reasonable limits, (7) conserving electricalpower, (8) using the correct number ofboilers for best efficiency at the required loadlevels, and (9) maintaining minimum excesscombustion air to the boilers.Maintaining a constant steam pressure isimportant to the overall efficiency of the engineeringplant. Wide or frequent fluctuations inthe steam pressure or degree of superheat aboveor below that for which the machinery is designedwill result in a considerable loss ofeconomy. Excessively high temperatures willresult in severe damage to superheaters, piping,and machinery.Proper acceleration and deceleration of themain engines are important factors in the economicaloperation of the engineering plant. Afast acceleration will not only interfere withthe safe operation of the boilers but will alsoresult in a large waste of fuel oil. The officer340