單項(xiàng)選擇題Black smoke coming from a boiler can be caused by ().

A.low water level
B.low oil pressure
C.excessively high fuel pressure
D.an improper air/fuel ratio


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1.單項(xiàng)選擇題Which of the following pumps belongs to centrifugal pump?()

A.Reciprocating pump
B.Screw pump
C.Diffuser pump
D.Water-ring pump

2.單項(xiàng)選擇題The advantage of a centrifugal pump as compared with a reciprocating pump is that ().

A.discharge is continuous
B.it has no internal valves
C.upon accidental closing of discharge valve, excessive pressure will not build up
D.all of the above are true

3.單項(xiàng)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

4.單項(xiàng)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)

5.單項(xiàng)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)

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A grease gun is generally used to lubricate a ().

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Which of the problems listed would came the discharge temperature of an R-12 refrigeration compressor to increase?()

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One cause of high head pressure occurring in a refrigeration system can be ().

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Which of the following problems could cause the high pressure cutout switch to shut down the compressor in a refrigeration system?()

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If the relief valve on the discharge side of a hydraulic pump lifts, the cause could be ().

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The temperature differential occurring between the inlet temperature of the fluid to be cooled and the outlet temperature of the cooling medium in a shell-and-tube heat exchanger is greatest in which of the flow designs listed?()

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If the head pressure of a reciprocating refrigeration compressor is excessive, ().

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If you are given the job of adding hydraulic fluid to a mooring winch, and are not certain as to the type of fluid to use, you should ().

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An internal bypass is provided on some hydraulic system suction strainers to help reduce the possibility of ().

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The amount of fluid friction or internal friction inherent in a mineral lubricating oil is reflected as a measure of its ().

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