單項選擇題A pump is said to have "negative suction head" when the pump is located ().

A.between the suction and discharge
B.below the liquid supply
C.above the liquid supply
D.any of the above


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1.單項選擇題

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.(1),(2)and(3)
D.(2)and(3)

2.單項選擇題

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)

3.單項選擇題A positive displacement pump is that where the volume of the pump chamber is alternately () to draw the liquid in and then () to force the liquid out.

A.increased;decreased
B.decreased;increased
C.decreased;decreased
D.increased;increased

4.單項選擇題The pressure head of a water pump is given in the unit of ().

A.kg
B.MPa
C.mH20
D.None of the above

5.單項選擇題

Which of the following are components of a mechanical seal? ()
(1) stationary ring
(2) rotational ring
(3) packing
(4)spring

A.(1), (2) and (3)
B.(1), (2) and (4)
C.(2), (3) and (4)
D.None of the above