# Steam Turbines Questions and Answers – Control and Supervisory Instruments

This set of Steam and Gas Turbines Multiple Choice Questions & Answers (MCQs) focuses on “Control and Supervisory Instruments”.

1. Radial vibration measurement measures ____________
a) unbalanced masses
b) cracked shafts
c) oil whirl
d) all of the mentioned

Explanation: Radial vibration measurement measures all the unbalanced masses, cracked shafts and also oil whirls.

2. Vibration measurements in steam turbines can be made in _______ planes.
a) 1
b) 2
c) 1 or 2
d) 4

Explanation: Vibration measurements in steam turbines can be measured in single plane or two planes.

3. Absolute shaft measurement is done when __________
a) weight of the rotating assemble is five times more than casing
b) weight of rotating assembly is two time more than the casing
c) weight of the rotating assembly is thrice the casing weight
d) none of the mentioned

Explanation: Absolute shaft measurement measures the shaft motion with respect to the free space. It is done when weight of the shaft assembly is five times more than the weight of casing.

4. Phase measurement is required for accurate balancing of the rotor.
a) True
b) False

Explanation: Phase measurement is required for accurate balancing of any rotor. Because phase is defined as angle between reference mark and heavy spot on the rotor.

5. Eccentricity measurement is used to indicate ______
a) bent shafts
b) when the rotor can be bought to the high speeds
c) bent shafts and when the rotor can be bought to the high speeds
d) none of the mentioned

Explanation: Eccentricity measurement makes us to know about the sag or bow in a rotor which helps us to get knowledge about whether to increase the speed or not.
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6. DE measurement is used to get the knowledge about distance between case and rotor.
a) True
b) False

Explanation: As turbine casing has more weight than the rotor, when turbine is under operation it should be taken care that there should not be any contact between turbine and casing due to thermal expansion as turbine has more expansion when compared to the casing.

7. Rotor thrust measurement is done in order to _______
a) monitor thrust
b) monitor bearing wear
c) monitor thrust & bearing wear
d) none of the mentioned

Explanation: Rotor thrust measurement is done in order to monitor thrust and also bears wear.

8. Thrust position measurements are taken within _____ inches of thrust bearing.
a) 10
b) 12
c) 20
d) 24

Explanation: Thrust position measurement is done within 12 inches of thrust bearing.

9. Thrust measurement taken out of 12 inches are effected by ______
a) thrust forces
b) thrust forces & thermal expansions
c) thermal expansions
d) none of the mentioned

Explanation: Measurements taken out of q2 inches are generally effected by thermal expansions.

10. Valve position measurement is used to measure how much valve is used.
a) True
b) False

Explanation: Valve position measurement is used to measure how much the valve is opened, mainly throttle valve which gives us information about how much percentage the load can be increased.

Sanfoundry Global Education & Learning Series – Steam and Gas Turbines.

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