CARGO PUMP PERFORMANCE VERSUS DESIGN CRITERIA

Abstract

ABSTRACTThis paper examines liquid cargo systems which are used on U.S. naval auxiliary ships and provides considerations for future designs. Specifying a pump which may be larger than required or oversizing transfer piping may create unexpected operating requirements which cause the system to be operated inefficiently and in a manner detrimental to pump life. A computer model of a typical three‐hose, three‐station FAS system was used to study centrifugal pump operation, under different conditions of delivery ship loading, for three fuels; Navy special fuel oil (NSFO), naval distillate (NATO symbol F‐76), and JP‐5 (NATO symbol F‐75). It is noted that many systems currently on naval auxiliaries were designed for use with NSFO, which is a highly viscous fuel in comparison to F‐76 and JP‐5.System curves were developed from the computer generated data and were superimposed on a graph of the appropriate pump curve for each fuel considered. This allowed predicting how the system would perform in actual operation and how the pump operates in actual use.The paper's conclusions indicate that the older pump design criteria have resulted in specifying cargo pumps that are rarely operated near their design point. An interesting phenomenon associated with the use of the GenSpecs‐specified recirculation line, equipped with pressure regulating valve, is also examined. Two new arrangements are proposed and their operation evaluated.