A.Pressure-reducing valveB.Unloading valveC.Counterbala……

单项选择题If a centrifugal bilge pump were continually operated with the discharge valve closed the （）.

A.motor overload would open
B.relief valve would open
C.pump would eventually overheat
D.motor would overheat

单项选择题In order to accurately measure very low pressures, which of the instruments listed should be used?（）

A.Compound gage
B.Bonrdon tube
C.Manometer
D.Deadweight gage

单项选择题Reduced capacity, accompanied by vibration and noise at the suction of a centrifugal pump is a result of （）.

A.cavitation
B.water hammer
C.fluid friction
D.steam knock

单项选择题The refrigerant leaves the evaporator of a refrigeration system as a low pressure （）.

A.sub-cooled liquid
B.high temperature liquid
C.oil saturated liquid
D.superheated vapor

单项选择题When operating with a negative suction head, which of the following types of pumps will require priming?（）

A.Reciprocating
B.Centrifugal
C.Rotary
D.Gear