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Hydraulic Machines Questions and Answers – Centrifugal Pumps


 1.What is the method of priming?

a) With a flooded suction

b) A bypass around the discharge check valve   

c)The foot  valve with auxiliary liquid supply

d) All of the above


2. In Priming, the removal of air by filling the pump passages i.e. flow passages e.g. The impeller and the volute casing with liquid.

a) True

b) False


3. For Smooth operation in centrifugal pump NPSHA should be -------- than NPSHR

a) Greater

b) Less


4. Adverse effects of cavitation include

a) Metallic erosion

b) Deterioration pump performance

c) Failure of pump components and Instability in flow pattern of pumping liquid

d) All of the above


5. Operating point gets at the intersection of System curve and Efficiency curve.

a) True

b) False


6. Flat curve

a) Shows little variation of head at all flows between design point & shut-off.

b) Head developed at shut-off is less than head developed at some flow between B.E.P & shut-off.

c) None of the above


Pump Curves - 6 Types of head vs flow rate curves

7. Mechanical losses are

a) Exclusively power loss takes place primarily in bearings, mechanical seals or gland packing.

b) Power loss is due to friction between the rotating faces of the impeller (or disc) and the liquid.

c) Both of the above


What is pump losses ? | What type of losses exists inside the centrifugal pump?

8. Steep curve

a) Large increase in head developed at shut-off from B.E.P

b) Head rises continuously from design point to shut-off.

c) Head developed at shut-off is less than head developed at some flow between B.E.P & shut-off.


9. It is difficult to start the motor due to

a) Voltage too low/power supply overloaded or supply frequency not correct.

b) Excessive total head on pump

c) Delivery flow too much


10. Motor gets jammed due to

a) Short circuit in motor or in starter

b) Excessive total head on pump

 c) Delivery flow too much  


11. When a pump vibrates, it indicates a problem.

a) True

b) False


12. Pump over heating is a normal occurrences.

a) True

b) False


13. Pump delivers insufficient / less capacity

a) Suction pipe / foot valve choked, defective or too small.

b) Number of revolutions too low

c) cavitiation in suction side,

d) All of the above


14. Insufficient pressure developed

a) Liquid contains too much gas or air or is too viscous.

b) Number of revolutions too low.

c) Number of revolutions too high or incorrect direction of rotation.

d) Impeller clogged / damaged / not of correct diameter and type

e) All of the above


15. Stuffing box leaks heavily

a) Shaft sleeve worn out in stuffing box region

b) shaft nuts untrue / shaft bent/ rotating parts not balanced properly or touching the casing

c) Excessive total head on pump

d) All of the above


16. Pump is noisy or vibrates excesevely

a) Ball bearings not of correct size or incorrectly fitted / have axial thrust.

b) Pump casing or pipe line under stress/ vibration of pipe Work.

c) Bearings dirty / rusty (corroded) or jammed.

d) All of the above


17. Bearings have short life

a)  Pump casing or pipe line under stress / vibrations of pipe work.

b) Bearings  rusty (corroded) or jammed.

c)  Delivery flow too much.     

d) All of the above.


18. Motor gets hot and burns out

a)Number of revolutions too low.

b)Bearing worn out / specified lubricant quantity and quality not maintained.

c)Ball bearings are of correct size or correctly fitted.

d)All of the above.


19.In Every day Routine Maintenance Chart For Pumps we should not check.

a)Visually check for leaks.

b)Check wear ring clearance.

c)Adjust gland as necessary to maintain slight leakage.

d) Check for vibration.


20.In Half yearly Routine Maintenance Chart For Pumps we should check.

a)Check the seal and flushing system condition.

b)Check shaft or shaft sleeve for scoring gland pack pumps.

c)Check alignment of pump and motor.

d)All of the above.


21.In pump vibration occurs due to

a. Problem in Operation

b. Problem in erection

c. None of the above

d. Both a & b


Must read related posts

Cavitation formation in pump

Function of volute casing in pump

Why use Mechanical seal ?

Gland seal vs. Mechanical seal

What are the types of pump ?

Boiler feed pump operation questions

Boiler feed pump starting procedure

How to calculate suction head in centrifugal pump

Coolant and lubricant

Pump Affinity law















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