Positive displacement, helical gear(斜齿轮) pumps are well suited for pumping oil because ______.

试卷相关题目

• 1Among the basic categories of equipment, which of the following are used to allow the hydraulic energy to be controlled、

  A.hydraulic pumps

  B.valves

  C.hydraulic cylinders

  D.hydraulic motors

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• 2When securing a flash-type evaporator for an extended period of time, you should ______.

  A.fill the unit with saltwater

  B.fill the unit with descaling compound

  C.completely drain the unit

  D.tightly seal the unit to exclude air

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• 3When a vacuum boiling evaporator works, the hot jacket water will pass over the tube stack and ___ the sea water passing through the tubes.

  A.dispose

  B.dissolve

  C.heat

  D.dissipates

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• 4Dirty oil must be _____ before being used again.

  A.mixed with clean oil

  B.purified

  C.heated

  D.strained

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• 5Great care is dedicated to the removal of _____ from the scavenge air.

  A.gravity

  B.viscosity

  C.density

  D.humidity

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• 6The oil in a cargo winch gear box should be sampled periodically(周期性地) to ______.

  A.prevent the gear box from leaking

  B.prevent the oil from becoming inflammable(易燃的)

  C.make sure it has not become contaminated(污染)

  D.make sure the motor bearings are lubricated

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• 7If an anchor windlass has been idle for some time, you should ______.

  A.repack all valve stems

  B.lubricate it prior to use

  C.replace the foundation bolts

  D.balance the warping heads

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• 8A mooring winch should be equipped with mechanical brakes capable of holding ______.

  A.half the breaking strength of the mooring line

  B.the full breaking strength of the mooring line

  C.the maximum expected tension(张力) of the mooring line

  D.50% over the working tension of the mooring line

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• 9Hydraulic cranes must be properly warmed-up before being operated because ______.

  A.warm-up allows the hydraulic system to become charged with oil

  B.warm-up allows the relief valves to be properly tested

  C.hydraulic strainers operate only during the warm-up period

  D.hydraulic fluid must be at the proper viscosity

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• 10The current flowing first in one direction and then in another is called ____ current.

  A.a rush

  B.an alternating

  C.a direct

  D.an exciting

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