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单选题
If a centrifugal pump vibrates and is noisy when operating, the cause could be （）.
A
worn gland sealing shaft
B
worn wearing rings
C
a bent shaft
D
reversed pump coupling
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diameter of the suction piping, with all other factors remaining the sameC
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set the relief valveB
check the lubrication systemC
vent the pump casingD
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pay attention to operating parametersB
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check oil level in separator to prevent overloadD
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单选题If you were operating a centrifugal water service pump with worn wearing rings, the （）.A
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单选题If a centrifugal pump is driven by a constant speed electric motor and produces a discharge pressure less than designed, the cause is probably（）.A
excessive pump speedB
excessive suction headC
worn wearing ringsD
gross pump misalignment
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单选题The purpose of the wearing rings used in a centrifugal pump is to （）.A
prevent an internal explosion in the pump when it is overheatedB
enable a visual inspection of the pump while it is runningC
insure a proper alignment of the pump coupling to the driverD
accommodate for friction between the impeller and the easing
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positive headB
negative suction headC
mechanical sealD
vent valve attached to the casing at the top of the volute
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单选题A centrifugal pump may fail to deliver water when first started if the （）.A
water seal pipe is pluggedB
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单选题Excessive air leakage into the suction side of a centrifugal pump would be indicated by which of the following operational problems?（）A
The pump delivers full capacity when started, but gradually slackens off toan abnormally low flowB
The pump packing gland overheats after short operating periodsC
The motor over-current protective device continually shuts the pump downD
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单选题Which of the following pumps belongs to centrifugal pump?（）A
Piston pumpB
Screw pumpC
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closedB
opened fullyC
cracked openD
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单选题The simplest method to use for determining if a centrifugal pump is operating as designed, is to （）.A
closely observe the pump discharge temperatureB
close off the discharge valve, and watch for a rise in pressureC
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centrifugal pump makes maintenance easier than reciprocating pump doesD
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单选题A centrifugal pump vibrates excessively during operationUpon disassembling the pump it is found that the impeller is out of balanceWithout an available spare, you should （）.A
drill holes through the heavy side of the impeller until it balancesB
weld counterweights to the light side of the impellerC
remove metal from the heavy side by machining in a latheD
acid wash and serape the heavy side until it balances
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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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