What causes cavitation in centrifugal pump ?

Related Mcqs:

1. Cavitation in a pump creates so many undesirable effects. Out of the following, which is not an undesirable effect created by cavitation ?

   A. Decrease in effect
   B. Increase in thrust
   C. Develops noise
   D. Develops high pressure

2. A centrifugal pump is used to pump water through a horizontal distance of 150 m, and then raised to an overhead tank 10 m above. The pipe is smooth with an I.D of 50 mm. What head (m of water) must the pump generate at its exit E. to deliver water at a flow rate of 0.001 m3/s? The Fanning friction factor, f is 0.0062 ?

   A. 10 m
   B. 11 m
   C. 11.8 m
   D. 30 m

3. A centrifugal pump used to pump water is used to pump an oil with specific gravity of 0.8 at the same rate. The power consumption will now_________________?

   A. Increase
   B. Decrease
   C. Remain same
   D. Data insufficient to predict

4. A centrifugal pump designed to pump water is employed to pump a more viscous oil. In the later case, the pump_________________?

   A. Develops a lower head
   B. Capacity is reduced
   C. Requires more power
   D. All A., B. and C.

5. Cavitation occurs in a centrifugal pump when the suction pressure is________________?

   A. Less than the vapour pressure of the liquid at that temperature
   B. Greater than the vapour pressure of the liquid at that temperature
   C. Equal to the vapour pressure
   D. Equal to the developed head

6. In centrifugal pump operation, the cavitation can be eliminated by maintaining suction pressure ______________ the vapor pressure of the liquid at the suction temperature?

   A. Lower than
   B. Higher than
   C. Equal to
   D. None of these

7. Cavitation in a centrifugal pump can be avoided by keeping the__________________?

   A. Inlet pressure high
   B. Outlet pressure low
   C. Inlet pressure low
   D. Outlet pressure high

8. A centrifugal pump is called a turbine pump, if it is having a_________________?

   A. Turbine type impeller
   B. Vaned diffusion casing
   C. Rotating vaned volute
   D. None of these

9. Which is the correct relationship for a centrifugal pump? (Where, D = Impeller diameter, inches H = Head developed, ft of liquid pumped N = Speed of pump, rpm) ?

   A. D = 1840 H0.5/N
   B. D = 1840 N/H0.5
   C. H = 1840 D0.5/N
   D. D = 1840 H/N

10. Specific speed of a centrifugal pump relates it with another pump having the___________________?

    A. Dynamic similarity
    B. Same efficiency
    C. Same speed
    D. Geometrical similarity