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

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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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• 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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• 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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• Which of the following pumps will build up a bursting pressure or stall their motors if the discharge valves are closed?（） (1) gear (2) centrifugal (3) screw

  A . （1）and（2） B . （1），（2）and（3） C . （1）and（3） D . （2）and（3）

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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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• 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 up

  A . （1），（2） B . （2），（3） C . （1），（2），（3） D . （2）only

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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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• If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.

  A . open；short；after B . closed；short；after C . open；long；before D . closed；long；before

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• 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 same B . diameter of the suction piping, with all other factors remaining the same C . width of the impeller only D . diameter of the impeller

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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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• 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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• Which of the following problems will occur if a disk-type centrifugal lube oil purifier is not properly primed prior to admitting oil flow to the bowl?（）

  A、Contamination of the lube oil by emulsification will result B、The lube oil will not be subjected to the proper centrifugal force C、The lube oil will overheat and flash D、Oil will discharge from the heavy phase discharge port and be wasted.

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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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