centrifugal pump mcqs questions and answers

Q1.How is water traveling along the shaft of a centrifugal pump prevented from entering the shaft bearing?

A.Shaft seal

B.Water flinger

C.Drain hole

D.Lantern ring


B

Q2.Why are removable sleeves installed on centrifugal pump shafts?fre

A.They make it easier to replace the pump shaft packing.

B.They can be economically replaced as they wear out.

C.They can be removed when it is necessary to lighten the weight of the pump.

D.They increase the strength of the shaft.


B

Q3.Which of the listed types of pumps is NOT likely to be installed in a main drainage or evacuation system?

A.Reciprocating pump

B.Centrifugal pump

C.High pitch rotary vane pump

D.Eductor pump


C

Q4.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 speed

B.excessive suction head

C.worn wearing rings

D.gross pump misalignment


C

Q5.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 rings


D

Q6.A centrifugal pump may fail to deliver water when first started if the _.

A.water seal pipe is plugged

B.pump is not primed

C.seal ring is improperly located

D.impeller is flooded


B

Q7.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


C

Q8.A centrifugal pump vibrates excessively during operation. Upon disassembling the pump it is found that the impeller is out of balance. Without an available spare, you should __.

A. drill holes through the heavy side of the impeller until it balances

B.weld counterweights to the light side of the impeller
C.remove metal from the heavy side by machining in a lathe

D. acid wash and scrape the heavy side until it balances


C

Q9.In order to properly remove air from the casing of a centrifugal pump when starting, the pump should have a _______.

A. positive head

B.negative suction head

C. mechanical seal

D. vent valve attached to the casing at the top of the volute


D

Q10.Most pump manufacturers recommend that the suction piping dimension for centrifugal pumps be __.

A.one size smaller than the pump suction nozzle

B. the same size as the pump suction nozzle

C. one size larger than the pump suction nozzle

D. installed with a short radius elbow at the pump


C

Q11.Most pump manufacturers recommend that the discharge piping for centrifugal pumps be one size larger than the pump discharge nozzle to __.

A. reduce the pump discharge pressure

B. reduce the frictional losses due to fluid flow

C. increase the pump discharge pressure

D. allow rapid venting of entrained air


B

Q12.Clearances between the impeller hub and casing of a centrifugal pump are checked with the use of _.

A. wooden wedges

B.an accurate set of feeler gages

C. a machinist’s rule

D. a depth micrometer


B

Q13.The basic function of the centrifugal pump impeller is to

A. directly increase the pressure of the liquid being pumped

B. directly increase the velocity of the liquid being pumped

C. convert the potential energy of the liquid to kinetic energy

D. separate air from the liquid being pumped


B

Q14.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. accomodate for friction between the impeller and the casing


D

Q15.In which of the following descriptions would centrifugal pump impeller cavitation most likely occur if the impeller diameters, rotating speed, and liquid temperature are the same?

A. In the second stage of a two-stage pump.

B. A single-stage impeller with straight vanes

C.A single-stage impeller with curved vanes.

D. A two-stage pump with an operating speed 100 RPM less than specified.


C

Q16.A lantern ring is _____.

A. the bottom ring in a set of piston rings

B. the oil slinger on a spring bearing

C. used to distribute seal water throughout the pump stuffing box

D. the lifting ring on each running light


C

Q17.The pump packing gland has been repeatedly tightened by small increments until the gland has bottomed. Which of the actions listed should be carried out next if the leakage continues to be excessive?

A. Replace all of the packing.

B. Replace with larger cross-sectional turns of packing.

C. Replace the soft packing with packing turns that are covered with lead wrap.

D. Continue to add more turns of packing


D

Q18.Air leakage between the shaft and stuffing box packing in a centrifugal pump is prevented by __.

A. a compressed packing gland

B. lantern rings between the packing rings

C. a liquid seal

D. the stuffing box gland


C

Q19.Which of the following centrifugal pump components converts the liquid kinetic energy of velocity to the potential energy of pressure?

A. Impeller

B. Electric motor

C. Volute

D. Eye


C

Q20.One of the consequences in continuing to operate a centrifugal bilge pump with the discharge valve closed, is that the

A.motor overload will open

B.relief valve will openB.The suction strainer is clogged.

C.pump will overheat

D.motor will overheat


C

Q21.If an operating bilge pump is developing good vacuum, but is unable to discharge any water, which of the following problems is the most probable cause?

A.The wearing rings are excessively worn.

B.The suction strainer is clogged.

C.The discharge valve is clogged.

D.The shaft is worn.


B

Q22.In a centrifugal pump, the seal piping directs liquid from the discharge side of the pump to the _____

A.Packing gland

B.Wearing ring

C.Stuffing

D.Lantern Ring


D

Q23.Which of the following statements is true concerning centrifugal pumps?

A.They are particularly suited for pumping high viscosity fluids.

B.They are started with the discharge valve opened.

C.The flow of liquid is developed by imparting energy due to the rotation of an impeller.

D.They are always mounted in a horizontal position.


C

Q24.A centrifugal pump attempting to develop flow against a closed discharge valve has a/an __.

A.capacity of 0%

B.efficiency of 100%

C.internal slippage of 0%

D.shut off horsepower rating of 100%


A

Q25.If a centrifugal pump operating with a positive suction head becomes air bound, your FIRST response should be to _____

A.vent the casing

B.close the discharge

C.tighten the packing

D.reprime the pump


A

Q26.Excessive wear on a centrifugal pump shaft sleeve will

A. cause severe vibration when the pump is operating

B. cause excessive leakage past the packing gland

C. cause damage in the stuffing box


B

D.allow interstage leakage in the pump casing glands

Q27.A crackling noise coming from a centrifugal pump casing is an indication of ___.

A. insufficient packing

B. an oversized lantern ring

C. excessive suction lift

D. reversed pump rotation


C

Q28.Radial thrust developed in high pressure centrifugal pumps can be eliminated by the use of _.

A. single volutes

B. a single diffusion nozzle

C. a diffusion ring

D. a modified Kingsbury thrust bearing


C

Q29.When shifting suction from one fresh water tank to another, if the fresh water pump loses suction you should___________.

A.Loosen the mechanical seal

B.vent the pump casing

C.check the discharge strainers

D.all of the above


B

Q30.Which of the listed types of seals is used effectively for pumps handling toxic or highly flammable liquids that cannot be permitted to escape into the atmosphere?

A.Conventional stuffing box

B.External mechanical seal

C.Double mechanical seal

D.Rubber bellows mechanical seal


C

Q31.Foot valves are primarily designed to __.

A.give a pump motor or driver positive protection when operating in a shutoff condition

B. provide a means of supplying sealing fluid for the impeller shaft stuffing box

C. enable a pump and its suction line to remain primed prior to starting the pump

D. afford the pumping system protection against water hammer and surging


C

Q32.To maintain design discharge pressure from a centrifugal pump, the design clearance must be maintained between the——

A. shaft and impeller

B. motor and pump shaft

C. casing and impeller wearing rings

D. lantern ring and impeller


C

Q33.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


A

Q34.If you heard a “crackling” sound occuring within a centrifugal pump, the most probable source of the noise would be the __.

A. shaft sleeves

B. discharge volutes

C. wearing rings

D. pump suction


D

Q35.The factors that determine the service life of packing in a pump will include which of the following conditions?

A. type of pump

B. condition of the shaft

C. length of time in use

D.all of these


D

Q36.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


B

Q37.To maintain design discharge pressure from a centrifugal pump, the design clearance must be maintained between the __.

A. shaft and impeller

B. motor and pump shaft

C. casing and impeller wearing rings

D. lantern ring and impeller


C

Q38.The static suction lift of a pump is the difference in elevation between the _.

A. centerline of the pump and the level of the liquid in the suction well when the source of liquid is below the pump

B. centerline of the pump and the suction liquid level when the source of liquid is above the pump

C. centerline of the pump and the level of the discharge liquid

D. liquid levels of the suction and discharge


A

Q39.Lantern rings are provided on centrifugal pumps to __.

A. allow illuminated inspection of shaft and packing

B. provide a passage for the stuffing box sealing liquid

C. adjust leakage at the shaft gland

D. allow for distortion of the wearing rings


B

Q40.The seal piping obtains liquid from the discharge side of the pump and directs the liquid to the _.

A. packing gland

B. wearing ring

C. stuffing

D. lantern ring


D

Q41.If a centrifugal pump is driven by a constant speed prime mover and produces a flow rate less than the designed specifications, the cause could be _.

A. suction absolute pressure greatly exceeds corresponding vapor pressure of liquid being pumped

B. excessive suction head

C. pump packing gland misalignment

D. worn wearing rings


D

Q42.A liquid is being transferred by a centrifugal pump. As the liquid passes through the volute, its velocity decreases and __.

A. its pressure increases

B. its pressure decreases

C. the potential energy decreases

D. the kinetic energy increases


A

Q43.Mechanical shaft seals used on water service pumps require lubrication of the seal faces to minimize deposits of foreign matter on those surfaces. Which of the following pressures and lubricants are required?

A. Water under negative pressure

B. Water under positive pressure.

C. Oil under positive pressure.

D. Oil under negative pressure


B

IQ44.f a centrifugal pump develops insufficient discharge pressure as a result of worn wearing rings, which of the following corrective actions is required?

A. Replace the rings

B. Throttle in on the discharge valve.

C. Always replace the wearing rings and the impeller as a set

D. Throttle in on the suction valve


A

Q45.Reduced capacity, accompanied by vibration and noise at the suction of a centrifugal pump, results from cavitation in the fluid being pumped. Cavitation describes the formation of _.

A. vapor pockets

B. water hammer action

C. fluid friction

D. steam knock


A

Q46.After renewing spiral packing in a centrifugal pump stuffing box, the packing should be seated, then the packing gland nuts _.

A. left in that position

B. loosened until the gland clears the stuffing box

C. tightened to compress the packing

D. loosened, and then retightened until they are only finger tight


D

Q47.A centrifugal pump gradually develops insufficient discharge pressure. What corrective action is required?

A. Replace the wearing rings

B. Throttle in on the discharge valve.

C.Replace the wearing rings, shaft, and impeller.

D. Throttle in on the suction valve.


A

Q48.If a centrifugal pump were continually operated with the discharge valve closed, the _.

A. motor controller overload would open

B. pump would eventually overheat

C. relief valve would continuously cycle open

D. motor would overheat


B

Q49.Pitting in the suction areas of a centrifugal pump bronze impeller is usually caused by __.

A. cavitation

B. electrolysis

C. abrasion

D. corrosion


A

Q50.If it were necessary for you to frequently replace the packing on the main condensate pump, the trouble could be the result of __.

A. running at low speed for a long time

B. excessive condensate recirculation

C. defective casing gasket

D. worn bearings


D

Q51.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


A

Q52.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


C

Q53.The centrifugal pump component responsible for converting the mechanical energy of the liquid being pumped, to that of kinetic energy is the __.

A. electric motor

B. volute

C. impeller

D. diffusion nozzle


C

Q54.Charring or glazing of the inner circumference of the packing rings in a centrifugal pump, is caused by _.

A. undertightening the packing

B. failure to seat the packing rings

C. insufficient lubrication of the packing

D. packing ring rotation


C

Q55.The discharge head of a centrifugal pump will vary directly with the __.

A. change in impeller diameter

B. square of the impeller diameter

C. cube of the impeller diameter

D. impeller efficiency for large changes in the size of the impeller


B

Q55.Permanent centrifugal pump shaft damage due to erosion, corrosion, and wear at the stuffing box is usually prevented by ____.

A. wearing rings

B. renewable sleeves

C. a hardened sprayed metal coating

D. internally flooded lantern rings


B

Q56.To absorb the wear resulting from impeller rotation and abrasives in the liquid, a centrifugal pump is usually fitted with ___.

A. lantern rings

B. bearings

C. casing volutes

D. wearing rings


D

Q57.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 rings


D

Q58.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


A

Q59.If a centrifugal pump operating with a positive suction head vibrates, or becomes noisy, the cause could be __.

A. excessive pump speed

B. worn wearing rings

C. air leakage into suction line

D. insufficient venting


D

Q60.Water leaking from a pump packing gland is kept away from the bearing housing by the use of __.

A. shaft sleeves

B. lantern rings

C. water flingers

D. water seals


C

Q61.The function of seal cages, or lantern rings installed in the centrifugal pump stuffing boxes, is to __.

A. cool the shaft

B. lubricate the packing

C. seal air from entering along the shaft

D. distribute the sealing liquid within the stuffing box


D

Q62.The brake horsepower of a centrifugal pump will vary directly as the _.

A. diameter of the impeller

B. square of the diameter of the impeller

C. cube of the diameter of the impeller

D. impeller efficiency for large changes in the size of the impeller


C

Q63.The diffusion ring installed in many high pressure centrifugal pumps, such as feed pumps, __.

A. eliminates axial thrust

B. imparts kinetic energy to the water passing through the pump

C. alleviates the need for a double suction impeller

D. eliminates radial thrust to the impeller


D

Q64.To prevent air pockets from forming in a centrifugal pump suction line installed angled from normal, any gate valve should be installed with the __.

A. bonnet above suction pipe centerline

B. centerline above the suction pipe centerline

C. stem pointing upward at right angles to the pipe

D. stem horizontal or pointing downward below the pipe


D

Q65.centrifugal pump designed to handle a liquid with a temperature of 120°C or greater must be provided with _.

A. a semi-mechanical seal

B. helical grooved wearing rings

C. self adjusting packing

D. a liquid seal line


D

Q66.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


C

Q67.The primary function of a centrifugal pump volute is to _.

A. develop a high velocity liquid

B. convert velocity to pressure

C. limit hydraulic end thrust

D. initiate flow


B

Q68. Which of the materials listed is used as the dynamic seal material on mechanical seals installed on most centrifugal pumps used in water service?

A. Copper.

B. Copper and carbon

C. Carbon

D. Bronze


C

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