# Mechanical Operations Questions and Answers – Draft Tubes

This set of Mechanical Operations Question Paper focuses on “Draft Tubes”.

1. How does the return flow to an impeller approaches the impeller?
a) From above
b) From below
c) From center
d) From all directions

Explanation: The return flow to an impeller of any type approaches the impeller from all directions because it is not under the control of solid surfaces.

2. Impeller mixers should always have draft tubes.
a) True
b) False

Explanation: In most cases of impeller mixer it is not a limitation but when the direction of flow and the suction to the impeller are to be controlled, draft tubes are used.

3. Draft tubes help to control ________________
a) Only the direction of flow
b) Only the suction to the impeller
c) The direction of flow and suction
d) Neither direction of flow nor suction

Explanation: The purpose of using draft tubes is to control the direction of flow and the suction to the impeller. It is not a limitation to the use of impeller in most cases.

4. In a propeller, where are the draft tubes mounted?
a) Immediately above the impeller
b) Immediately below the impeller
c) Around the impeller
d) On the impeller

Explanation: Draft tubes for propeller are mounted around the impeller, and those for turbines are mounted immediately around the impeller.

5. In a turbine, where are the draft tubes mounted?
a) Immediately above the impeller
b) Immediately below the impeller
c) Around the impeller
d) On the impeller

Explanation: Draft tubes for propeller are mounted around the impeller, and those for turbines are mounted immediately above the impeller.

6. Using draft tubes is a limitation?
a) True
b) False

Explanation: It is not a limitation to the use of impeller in most cases. The purpose of using draft tubes is to control the direction of flow and the suction to the impeller.

7. Shown figure illustrates _______

a) Turbine
b) Propeller
c) Baffleless tank
d) Agitation vessel

Explanation: Draft tubes for propeller are mounted around the impeller, and those for turbines are mounted immediately above the impeller. As clearly visible in the image the draft tubes are around the impeller hence it is a propeller.

8. Shown figure illustrates _______

a) Turbine
b) Propeller
c) Baffleless tank
d) Agitation vessel

Explanation: Draft tubes for propeller are mounted around the impeller, and those for turbines are mounted immediately above the impeller. As clearly visible in the image the draft tubes are immediately above the impeller hence it is a turbine.

9. Use of draft tubes _________________
a) Add to the fluid friction
b) Have no effect on fluid friction
c) Reduce fluid friction
d) Depend on the type of Fluid

Explanation: Draft tubes add to the fluid friction in the system, and for a given power input, they reduce the rate of flow, so they are not used unless required.

10. Use of draft tubes _________________
a) Increase the rate of fluid flow
b) Decrease the rate of fluid flow
c) Have no impact on the rate of flow
d) Depends on the type of fluid

Explanation: Draft tubes add to the fluid friction in the system, and for a given power input, they reduce the rate of flow, so they are not used unless required.

Sanfoundry Global Education & Learning Series – Mechanical Operations.

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