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单选题
The amount of fluid delivered by a centrifugal pump can be regulated by （）.
A
throttling the pressure line
B
changing the speed of the rotor
C
either A or B
D
None of the above is tree
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单选题Which of the following statements about pump operations is NOT a correct statement?（）A
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A substance must be cold in order for it to be pumpedC
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diameter of the discharge piping, with all other factors remaining the sameB
diameter of the suction piping, with all other factors remaining the sameC
width of the impeller onlyD
diameter of the impeller
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单选题All of the following steps are taken in starting a centrifugal pump，EXCEPT to（）.A
set the relief valveB
check the lubrication systemC
vent the pump casingD
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单选题The pump has a constant stroke and the amount of fuel delivered is regulated by rotating （） which has a specially arranged helical groove cut into it.A
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the pump camC
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单选题The capacity of a centrifugal pump can be increased by the installation of a larger diameter impeller Another means of increasing the pump capacity is to （）.A
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increase the size of the cardent assemblyC
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contaminated fluidB
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worn pintle bearingsD
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单选题The purpose of the wearing rings used in a centrifugal pump is to （）.A
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enable a visual inspection of the pump while it is runningC
insure a proper alignment of the pump coupling to the driverD
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assembledD
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centrifugal pump is cheaper than reciprocating pumpB
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单选题The amount of fluid delivered by a positive displacement pump can be regulated by （）.A
throttling the pressure lineB
changing the speed of the driving rotorC
either A or BD
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单选题Which of the listed conditions can lead to cavitation气穴in a centrifugal pump?（）A
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Worn wearing ringsD
Heavy fluid in the flow stream
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单选题Why are removable sleeves installed on centrifugal pump shafts?（）A
They make it easier to replace the pump shaft packingB
They can be economically replaced as they wear outC
They can be removed when it is necessary to lighten the weight of the pumpD
They increase the strength of the shaft
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