A.positive head
B.negative suction head
C.mechanical seal
D.vent valve attached to the casing at the top of the volute
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A.gate valve
B.globe valve
C.check valve
D.plug cock
A.At the designed operating temperature, the liquid refrigerant charge has changed to a vapor
B.The liquid refrigerant tends to collect at the bellows or diaphragm and reduces the valve sensitivity
C.The sensing bulb is empty of liquid refrigerant charge at the designed operating temperature
D.The sensing bulb is never emptied of liquid refrigerant under normal operating conditions
A.diaphragm type gage
B.pressure transducer
C.manometer
D.All of the above
A.reduce radial thrust to the impeller
B.double the liquid velocity through the pump when compared to a single volute
C.reduce hydraulic end thrust
D.provide the effect of multi-staging
A.dirt will cause corrosion of bearing
B.bearings will leak oil excessively
C.dirt is very abrasive when mixed with grease
D.grease will become inflammable
最新試題
Thermostatic expansion valves can be adjusted for （）.
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
If the viscosity of the liquid being transferred remains constant as the discharge pressure increases, the rotary pump （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
The general purpose of a heat exchanger is to （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
If the suction pressure at the refrigeration compressor is below normal, the cause can be（）.
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.