A centrifugal bilge pump requires priming （）.

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• The purpose of the wearing rings used in a centrifugal pump is to （）.

  A . prevent an internal explosion in the pump when it is overheated B . enable a visual inspection of the pump while it is running C . insure a proper alignment of the pump coupling to the driver D . accommodate for friction between the impeller and the easing

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• 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 improve B . discharge to be reversed C . efficiency to decrease D . slippage to decrease

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• 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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• Which of the following actions should be taken if during a routine maintenance inspection of a centrifugal pump, localized scoring on a pump shaft sleeve is detected?（）

  A . Correct the cause of the scoring and repair the sleeve or replace with a new one B . Reassemble the unit and provide more water leak off for proper lubrication C . Check for parallel alignment of the sleeve radial faces to the sleeve bores D . Reassemble the unit and adjust the governor to obtain a slower speed

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• The usual symptoms of cavitation in a centrifugal pump is （）.

  A . noise and vibration B . an increase in discharge pressure C . an increase in suction pressure D . lifting of the relief valve

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• Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by （）.

  A . cavitation B . electrolysis C . abrasion D . corrosio

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• A multistage centrifugal pump can be BEST described as having （）.

  A . two or more impellers housed together in one casing and mounted on a single shaft B . a single stepped impeller mounted in a progressively staged casing C . a large radial clearance between the impeller and casing to prevent overheating due to D . an increase in the discharge velocity of the liquid with a corresponding decrease in pressure through the stage

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• A double suction centrifugal pump impeller has been installed in the reverse direction, and will （）.

  A . have a greater head capacity B . operate with increased impeller efficiency C . discharge through the suction side of the pump casing D . require more power to run the shaft

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• What is a function of the wearing rings used in most centrifugal pumps?（）

  A . Absorb erosion of high velocity discharge stream B . Seal pump shaft against entry of air C . Isolate the discharge side from the suction side D . Dampen the turbulent discharge flow

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• If the capacity of a centrifugal pump decreases gradually over a long period of time, you should replace the （）.

  A . packing gland B . mechanical seals C . lantern rings D . wearing ring

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• Which features of a centrifugal pump reduce the need for renewing worn impellers and pump casings?（）

  A . Close radial clearance between impeller hub and casing B . Low rotational speed of impeller C . Removable end plate D . Replaceable impeller and casing wearing ring

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• The function of a centrifugal pump double volute casing is to （）.

  A . reduce radial thrust to the impeller B . double the liquid velocity through the pump when compared to a single volute C . reduce hydraulic end thrust D . provide the effect of multi-staging

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• When installed for bilge pumping or ballast duty, centrifugal pumps require a （） to remove air from the suction pipe.

  A . air chamber B . head lank C . primer D . prime mover

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• What is a characteristic of all centrifugal cargo pumps? （）

  A . They are self-priming B . Decreasing the speed of rotation will decrease the discharge pressure C . Opening the discharge valve wider will increase the discharge pressure D . All of the above

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• If a bilge pump failed to build up discharge pressure, you should check for （）.

  A、The requirement for the oil content of bilge water discharged is 15 ppm. B、No discharge in sensitive waters. C、Any discharge in sensitive waters. D、International, national or local requirements have to be observed.

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• The fire pumps must be capable of delivering a total quantity of water at a defined head, not less than （） of the total bilge pumping capacity.

  A . one-third B . two-thirds C . one-fourth D . two-fourth

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• When starting a centrifugal pump, the discharge valve should be （）.

  A . closed B . opened fully C . cracked open D . partly ope

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• The volute of centrifugal pump also acts as a diffuser converting （）into pressure head.

  A . mechanical energy B . heat energy C . potential energy D . kinetic head

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• A centrifugal pump can’t supply water after startingYou should check （）.

  A . priming water B . power supply C . packing gland D . bearing lubricatio

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• On modern ships, centrifugal pump with a self-primer has replaced reciprocating pump as bilge pump because（）

  A . centrifugal pump is cheaper than reciprocating pump B . the size of centrifugal pump with same capacity is smaller than that of reciprocating pump C . centrifugal pump makes maintenance easier than reciprocating pump does D . all of the above

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• 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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• The cleaned heated oil, after passing through the centrifuges, is to be pumped to a （）.

  A . settling tank B . service tank C . ballast tank D . drain tank

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• To operate a centrifugal fire pump at reduced capacity, you should （）.

  A . readjust the relief valve B . throttle the suction line C . throttle the discharge valve D . open the priming line

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• If you were operating a centrifugal water service pump with worn wearing rings, the （）.

  A . pump would be very noisy B . pump would vibrate excessively C . pump would develop insufficient flow D . stuffing box would leak excessively

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