Which of the following pumps are self-priming, and can deal with liquid from a level below the pump: （）
(1)reciprocating
(2)vane
(3)gear
A.（1）only
B.（1）and（2）
C.（2）and（3）
D.（1），（2）and（3）
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Which of the following will be the advantage of a centrifugal pump as compared with a reciprocating pump?（）
(1) Its discharge is continuous
(2) It has no internal valves
(3) Upon accidental closing of discharge valve, excessive pressure will not build up
A.（1），（2）
B.（2），（3）
C.（1），（2），（3）
D.（2）only
A.reduce
B.rise
C.raise
D.fall
A.increase discharge pressure
B.increase suction vacuum
C.develop pulsation flow
D.keep a steady rate of flow
A.slack enough to allow slight leakage of fluid
B.slightly clocked
C.brought up tight so as not to allow any leakage
D.fitted with a relief valve
A.Volute pump
B.Diffuser pump
C.Regenerative pump
D.All of the above
最新試題
Which of the listed pumps is NOT a positive displacement pump?（）
An increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be caused by （）.
Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?（）
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）
An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
If the head pressure of a reciprocating refrigeration compressor is excessive, （）.
The major source of chemical contaminants in hydraulic fluid is （）.
The output volume of a positive fixed displacement pump can be changed only by （）.
A gradual decrease in the discharge pressure of an operating hydraulic pump can be caused by （）.