# Hydraulic Machines Questions and Answers – Specific Speed Centrifugal Pumps

This set of Hydraulic Machines Multiple Choice Questions & Answers (MCQs) focuses on “Specific Speed Centrifugal Pumps”.

1. The energy usage of a pump is determined by _______
b) Power required
d) Isentropic expansion

Explanation: The energy usage of a pump is determined by power required. Thus, it plays an important role in determining the amount of energy that a pump dissipates during its operation. It is with respect to the length of time.

2. For an oil field to have solid control, it needs _______
a) Draft tubes
b) Throttle bush
c) Stuffing box
d) Centrifugal pumps

Explanation: For an oil field to have solid control, it needs centrifugal pumps. At each stage in the centrifugal pump, the fluid is directed to towards the centre. This makes it more efficient in operating a large oil field.

3. If we lower the temperature, the water pump cavitation ________
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: If we lower the temperature, the water pump cavitation decreases. This happens as the NPSH value reaches a safety margin.

4. Which among the following is not a centrifugal pump?
a) Sand pumps
b) Froth pumps
c) Slurry pumps
d) Energy pumps

Explanation: From the above, Energy pumps are not a type of centrifugal pump. At each stage in the centrifugal pump, the fluid is directed to towards the centre. The energy usage in pumping installation is determined by Friction characteristics. Thus, it is not a suitable option.

5. Centrifugal pumps work under the same principle, but differ in their _______
a) Working
b) Functions
c) Dimensions
d) Impeller

Explanation: Centrifugal pumps work under the same principle, but differ in their functions. At each stage in the centrifugal pump, the fluid is directed to towards the centre. The energy usage in pumping installation is determined by Friction characteristics.
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6. If we raise the liquid level in the suction vessel, cavitation ______
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: If we raise the liquid level in the suction vessel, cavitation decreases. This happens as the NPSH value reaches a safety margin.

7. Magnetic coupled pumps are also called as _________
a) Series pumps
b) Parallel pumps
c) Froth pumps
d) Drive pumps

Explanation: Magnetic coupled pumps are also called a magnetic drive pumps. They show a lot of difference in their traditional pumping style. It is connected by means of direct mechanical shaft.

8. Magnetic coupled pumps works via ________
a) Antiferromagnet
b) Drive magnet
c) Pump magnet
d) Ferromagnet

Explanation: Magnetic coupled pumps works via drive magnet. Magnetic coupled pumps are also called a magnetic drive pumps. They show a lot of difference in their traditional pumping style. It is connected by means of direct mechanical shaft.

9. When we change the pump, the cavitation ______
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: By changing the pump we can decrease the cavitation in the pump by bringing the NPSH value to a safety margin.

10. If we reduce the motor rpm in an impeller, cavitation _______
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: If we reduce the motor rpm in an impeller, cavitation decreases. This can be done by setting the NPSH value in the safety limit.

11. Decreasing the diameter of the eye of the impeller, cavitation _________
a) Increases
b) Decreases
c) Same
d) Independent

Explanation: Decreasing the diameter of the eye of the impeller, cavitation increases due to deviation from the safety limit.

12. No gland is needed for the centrifugal pump.
a) True
b) False

Explanation: No gland is needed for the centrifugal pump. This is because they have no direct connection between the motor shaft and the impeller, so there is not a requirement of gland in pumps.

13. Pump is always supported by bearings.
a) True
b) False

Explanation: Pump shaft is not always supported by bearings. Since the pumps have no bearing support. The pumps are provided with a housing. The inner walls of the pump are provided with bushings.

14. If we use an impeller inducer, we can reduce the cavitation in a centrifugal pump.
a) True
b) False

Explanation: Yes, If we use an impeller inducer, we can reduce the cavitation in a centrifugal pump by bringing the NPSH value to a safety limit.

15. There will be leakage only if there is ________
a) High pressure
b) High temperature
c) Froths are generated
d) Casing breakage

Explanation: Pumps have a major problem called as leakage. This might lead to a lot of losses during product manufacture. Thus, the leakage is mainly due to the breaking of the case. Thus, the correct option is casing breakage.

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