A.to fill 2 tanks at the same time
B.to use pump at a higher pressure
C.to return liquid to suction side if discharge valve is closed
D.All of the above are true
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A.injector
B.positive displacement
C.centrifugal
D.centripetal
A.injector pumps
B.positive displacement pumps
C.centrifugal pump
D.centripetal pumps
A.the mechanical seal
B.packed stuffing boxes
C.either A or B
D.neither A nor B
As for a hydraulic vane pump, which of the following is in contact with the vanes during working: （）
(1)the rotor
(2)the pump shaft
(3)the external surface of the housing
A.(1) only
B.(2) only
C.(1) and (2)
D.(1),(2)and(3)
A.circular
B.elliptical
C.rectangular
D.hexagon
A.suction
B.exhaust
C.pressure
D.discharge
A.draw the liquid in；force the liquid out
B.force the liquid out；draw the liquid in
C.suction；draw
D.deliver；outlet
A.throttling the pressure line
B.changing the speed of the rotor
C.either A or B
D.None of the above is tree
Which of the following pumps are self-priming, and can deal with liquid from a level below the pump? （）
(1) reciprocating
(2) rotary
(3) centrifugal
A.(1)only
B.(1)and (2)
C.(1),(2)and(3)
D.(2)and(3)
A.throttling the pressure line
B.changing the speed of the driving rotor
C.either A or B
D.None of the above is tree
最新试题
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
Which of the following statements is correct concerning heat transfer?（）
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, you should （）.
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 （）.
A pressure drop through the refrigerant liquid line may cause （）.
The major source of chemical contaminants in hydraulic fluid is （）.
The usual symptoms of cavitation in a centrifugal pump is （）.
The control mode in which the final control element is moved from one of two flexed positions to the other is known as （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）