Which of the valves listed will be cycled from fully open to fully closed when the handle is turned 90 degree、

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• 1The pressure of a liquid leaving the pump can be referred to as the ______.

  A.total head

  B.discharge head

  C.net positive suction head

  D.suction head

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• 2The gear and screw pumps are classified as______.

  A.variable stroke pumps

  B.multistage pumps

  C.positive displacement pumps

  D.triple-ported pumps

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• 3A feed pump for an auxiliary boiler might lose suction if the ______.

  A.boiler water level is low

  B.feed-water is too hot

  C.boiler steam demand is low

  D.feed-water is too cold

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• 4A firebox explosion in an automatically fired auxiliary boiler may be the result of ______.

  A.excessive purging before lighting off

  B.insufficient trail for ignition period

  C.a faulty transformer in the ignition circuit

  D.insufficient purging after lighting off

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• 5The water in a steaming auxiliary boiler should be tested daily for ______.

  A.dissolved oxygen

  B.chlorides

  C.sludge

  D.dissolved nitrogen

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• 6A pump shaft that is bent or distorted should normally be ______.

  A.repaired by a suitable welding process

  B.straightened by applying heat and torsion

  C.reconditioned by metallizing and machining

  D.replaced with a satisfactory spare

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• 7A centrifugal pump may fail to deliver water when first started if the ______.

  A.water seal pipe is plugged

  B.pump is not primed

  C.seal ring is improperly located

  D.impeller is flooded

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• 8Which of the following conditions must exist for heat to flow from one object to another、

  A.The two objects must be in physical contact.

  B.The two objects must be the same size.

  C.There must be an existing temperature differential.

  D.There must be an existing weight differential.

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• 9The dew point of air is reached when the wet bulb temperature is ______.

  A.twice the dry bulb temperature

  B.10℃ above the dry bulb temperature

  C.5℃ above the dry bulb temperature

  D.equal to the dry bulb temperature

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• 10If air at 95 ℃ dry bulb temperature and 50% relative humidity is conditioned to 75 ℃ dry bulb temperature and 50% relative humidity, it is an example of ______.

  A.cooling only

  B.cooling and humidifying

  C.cooling and dehumidifying

  D.adiabatic(绝热的) cooling

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