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
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should （）.
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?（）
Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.
Which of the listed pumps is NOT a positive displacement pump?（）
Which of the following statements is correct concerning heat transfer?（）
On tank vessels equipped with power operated cargo tank valves, the type of power operator most commonly used is （）.