A．the relief valve should open before the high pressure cutout
B．the relief valve should open and allow the excess refrigerant to flow to the receiver
C．the high pressure cutout switch should operate before the relief valve opens
D．you should close the discharging valve
[单选题]Low compressor head pressure in a refrigeration system can be caused by ___.A．insufficient condenser cooling waterB．excessive condenser cooling waterC．air in the refrigeration systemD．excessive refrigerant in the system
[单选题]If a reciprocating air compressor has a knock occurring in frequency with its operating RPM, the cause is probably _____.A．misalignment or worn main bearingsB．insufficient cylinder lubricationC．defective or poorly fitted valvesD．All of the above
[单选题]If the suction pressure at the refrigeration compressor is below normal, the cause can beA．refrigerant overchargeB．overfeeding by the expansion valveC．a restricted suction strainerD．due to short cycling of the compress
[单选题]（） the supercharge pressure is, （） power an engine develops.A . The higher；the moreB . Higher；moreC . Higher；littleD . The higher；the le
[单选题]The pressure differential across a diesel engine lube oil system duplex filter should be checked to ________.A．determine the need for filter cleaningB．measure any change in oil viscosityC．prevent damage to the filterD．determine the need for batch fil
[单选题]Loss of lubricating oil pressure to the main propulsion diesel engine will actuate a/an _____.A．over-speed tripB．audible/visual alarmC．the ships/boats general alarmD．reserve oil storage tank
[单选题]The pressure ________ causes Americans选择Thepressure________causesAmericanstobeenergetic,butitalsoputsthemunderaconstantemotionalstrain.A．)tocompeteB)competingC)tobecompetedD)havingcompeted
[名词解释] 水压力（hydraulic pressure）
[单选题]As a high pressure system approaches，the barometer reading（）.A . stays the sameB . fallsC . risesD . falls rapidly
[单选题]The highest pressure in a diesel engine cylinder normally occurs （）.A . at TDCB . before TDCC . after TDCD . during air starting