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单选题
The discharge rate or capacity of a centrifugal pump will vary directly as the （）.
A
change in the impeller diameter
B
square of the impeller radius
C
cube of the impeller diameter
D
impeller efficiency for large changes in its size
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单选题What is the function of wearing rings found on some centrifugal pumps? （）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
Oil is discharged from the impeller through the outletB
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Absorb erosion of high velocity discharge streamB
Seal pump shaft against entry of airC
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单选题A centrifugal bilge pump requires priming （）.A
primarily to lubricate the shaft sealsB
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to initially unload the pump by having its head pressure equal to discharge pressureD
in order to overcome the potential energy of water in the discharge line
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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
water hammerC
fluid frictionD
steam knock
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单选题Which of the following will be the advantage of a centrifugal pump as compared with a reciprocating pump?（） (1) Its discharge is continuous (2) It has no internal valves (3) Upon accidental closing of discharge valve, excessive pressure will not build upA
（1），（2）B
（2），（3）C
（1），（2），（3）D
（2）only
考题
单选题Most pump manufacturers recommended that the discharge piping for centrifugal pumps be （）.A
one size larger than the pump discharge nozzleB
the same size as the pump discharge nozzleC
one size smaller than the pump discharge nozzleD
installed with a short radius elbow at the pump
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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
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单选题Increasing the speed of a centrifugal pump will result in an increase in its capacity in its capacityAnother means of increasing the capacity 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
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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
open the pump suction and discharge valves
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单选题The usual symptoms of cavitation in a centrifugal pump is （）.A
noise and vibrationB
an increase in discharge pressureC
an increase in suction pressureD
lifting of the relief valve
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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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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To operate a centrifugal fire pump at reduced capacity, you should （）.A
readjust the relief valveB
throttle the suction lineC
throttle the discharge valveD
open the priming line
考题
单选题If the capacity of a centrifugal pump decreases gradually over a long period of time, you should replace the （）.A
packing glandB
mechanical sealsC
lantern ringsD
wearing rings
考题
单选题It is possible to mount a double suction centrifugal pump impeller with the vanes facing in the wrong directionThis would cause the pump （）.A
head capacity to improveB
discharge to be reversedC
efficiency to decreaseD
slippage to decrease
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When starting a centrifugal pump, the discharge valve should be （）.A
closedB
opened fullyC
cracked openD
partly open
考题
单选题The discharge head of a centrifugal pump will vary directly with the （）.A
change in impeller diameterB
square of the impeller diameterC
cube of the impeller diameterD
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考题
单选题One of the consequences in continuing to operate a centrifugal bilge pump with the discharge valve closed, is that the （）.A
motor overload will openB
relief valve will openC
pump will overheatD
motor will overheat
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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
momentarily close off the suction valve, and watch for a rise in pressureD
use a clamp on ammeter and compare the readings to past records
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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
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