Lesson15MarinePumps讲解.ppt

Wuhan Institute of Shipbuilding Technology;Lesson 15 Marine Pumps ;A pump is a machine used to raise liquids from a low point to a high point. Alternatively（换句话说） it may simply（仅仅） provide the liquid with an increase in energy enabling it to flow or build up a pressure. ;Pump types There are three main classes of pump in marine use: displacement pump（容积式泵，柱塞泵）, axial flow pump（轴流泵） and centrifugal pump（离心泵）. ;单缸单作用; 单作用叶片泵; 离心泵;Displacement Displacement pumps are those where the volume（容积） of the pump chamber（泵腔） is alternately（交替地） increased to draw the liquid in from the suction pipe（吸入管） and then decreased to force the liquid out into the delivery pipe（输出管）. ;The pump is double acting, that is liquid is admitted to either side of the piston where it is alternately drawn in and discharged. ;Above the piston, liquid is discharged and the suction valve（吸入阀） remains closed. As the piston travels down, the operations of suction and discharge occur now on opposite sides.;Suction valve closed;An air vessel（空气室） is usually fitted in the discharge pipework（排出管路） to dampen（消除，抑制） out the pressure variations（压力波动） during discharge. ;The peak（最高的） pressure energy（压力能） is thus stored in the air and returned to the system when the pressure falls.;A relief valve（安全阀） is always fitted between the pump suction chambers（吸入腔室） to protect the pump should it be operated with in the discharge line. ;They are however complicated（复杂的） in construction with a number of moving parts requiring attention（保养） and maintenance（维护）. ;The pump is self priming（自吸的）, but where possible to reduce wear（磨损） or the risk of seizure（卡住） it should be flooded with（注满） liquid before starting. ;A steam driven pump（蒸汽泵） will require the usual draining and warming through procedure before steam is gradually admitted.;Ridges（凸台） will eventually（最终） develop at the limits of the piston ring travel and these must be removed. The suction and discharge valves must be refaced（重修表面） or ground in（grind in，研磨） as requi