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单选题
If you heard a ‘crackling’ noise in centrifugal pump, the most probable cause of the problem would be（）
A
insufficient speed
B
cavitation
C
excess discharge pressure
D
excessive net positive suction head B
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单选题With respect to centrifugal pump impellers, which of the following descriptions represents the correct centrifugal pump classification? （）A
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单选题Which of the following statements is correct with regards to the operation of a centrifugal cargo pump?（）A
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a centrifugal fanB
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单选题Reduced capacity, accompanied by vibration and noise at the suction of a centrifugal pump is a result of （）.A
cavitationB
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单选题Most pump manufacturers recommended that the discharge piping for centrifugal pumps be （）.A
one size larger than the pump discharge nozzleB
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cavitationB
electrolysisC
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corrosion
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单选题Before attempting to put out a class “C” fire involving an electric-driven centrifugal pump, you should FIRST （）.A
insulate your shoesB
ground the fire hoseC
secure its power supplyD
start the fire pump
考题
单选题Increasing the speed of a centrifugal pump will result in an increase in its capacity Another means of increasing the capacity of a centrifugal pump is to increase the （）.A
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
考题
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One of the main functions of wearing rings, as used in a centrifugal pump, is to （）.A
maintain radial alignment between the pump impeller and casingB
absorb all impeller shaft end thrustC
prevent water leakage to the atmosphereD
prevent wear of the pump casing and/or impeller
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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
increase speedB
increase the size of the cardent assemblyC
reduce wearing ring clearancesD
change the pump to a close coupled arrangement
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pump would be very noisyB
pump would vibrate excessivelyC
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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
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throttle the suction lineC
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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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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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考题
单选题Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be （）.A
one size smaller than the pump suction nozzleB
the same size as the pump suction nozzleC
one size larger than the pump suction nozzleD
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考题
单选题Which of the following pumps belongs to centrifugal pump?（）A
Piston pumpB
Screw pumpC
Diffuser pumpD
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考题
单选题To maintain design discharge pressure from a centrifugal pump, the design clearance must be maintained between the （）.A
shaft and impellerB
motor and pump shaftC
casing and impeller wearing ringsD
lantern ring and impeller
考题
单选题On modern ships, centrifugal pump with a self-primer has replaced reciprocating pump as bilge pump because（）A
centrifugal pump is cheaper than reciprocating pumpB
the size of centrifugal pump with same capacity is smaller than that of reciprocating pumpC
centrifugal pump makes maintenance easier than reciprocating pump doesD
all of the above
考题
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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