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

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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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• A centrifuge will satisfactorily remove which of the following contaminants from fuel oil?（）

  A . Gasoline B . Water C . Lubricating oil D . sulphur compound

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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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• 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 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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• On a multistage flash-type evaporator, the flash chamber is （）

  A . combined as part of the salt water feed heater B . the open area above the brine levels in the first and second stages C . combined as part of the distillate cooler D . another term used to describe the vapor feed heater

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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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• On board supply vessels, a centrifuge is normally used to purify（）

  A . cooling water B . fuel oil C . sea water D . diesel intake air

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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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• A centrifugal impeller consists of a number of vanes curving （） from the direction of rotation.

  A . backwards B . forwards C . upward D . downward

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• One characteristic of a lubricating oil adversely affecting the result of centrifuging is （）

  A . high TBN value B . low oil floc point C . low oil demulsibility D . low oil neutralization number

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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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• A centrifugal bilge pump requires priming （）.

  A . primarily to lubricate the shaft seals B . due to the inability of this type of pump to lift water to cover the suction (eye) of the impeller C . to initially unload the pump by having its head pressure equal to discharge pressure D . in order to overcome the potential energy of water in the discharge line

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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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• A centrifugal compressor’s purge recovery unit（）

  A . reclaims water B . purges air without losing refrigerant C . purges air with some loss of refrigerant D . purges lube oil from the refrigerant

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• High-speed rotating in a centrifugal purifier can produce a force （） larger than the force of gravity.

  A . many thousand times B . between times C . one time D . at time

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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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• High-speed rotation in a centrifugal purifier can produce a force （） the force of gravity.

  A . many thousand times larger than B . the same as C . many thousand times smaller D . none of the above

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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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