A.injector pumps
B.positive displacement pumps
C.centrifugal pump
D.centripetal pumps
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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
最新試題
The general purpose of a heat exchanger is to （）.
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 output volume of a positive fixed displacement pump can be changed only by （）.
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 following statements is correct concerning heat transfer?（）
If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be （）.
A grease gun is generally used to lubricate a （）.
Heavy wear in a particular area of the inner circumference of a packing ring may be caused by （）.
Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?（）