Thermal Power Plant Interview Questions

Thermal Power Plant Interview Questions - Steam Turbine

Q.1 What is the difference between control oil & trip oil?

Ans. Trip Oil - Oil passes through some of protection relays to open ESV is called Trip oil

Turbine Trip Oil Circuit

Control Oil - Oil goes to for operation of HP, IP & LP valve actuators through I to H converters is called as control oil

Turbine Governing System

Q.2 Why the control oil temperature is more than lube oil ?

Ans.

To maintain low viscosity of the oil.
Because control & governing system internal parts have very low operating clearances.
So in order to maintain that control oil is not cooled & maintained its temperature around 60 deg
Actuators & ESV components are operating at very less clearance need low oil viscosity.
Actuators & ESV components are operating at very less clearance up to 50 microns.

Turbine Oil System

Q.3 Mesh size for lube oil & control oil filters ?

Ans.

Lube Oil Filter

Lube oil filter size is around 25 to 40 microns
Size depends on the minimum clearance in the bearings
Bearings clearance will be in the range of 200 microns to 500 microns

Bearing Clearance

Control Oil Filter

Control oil filters size is around 10 to 25 microns

Size depends on the minimum clearance in the HP & LP actuators

Actuators & ESV components are operating at very less clearance up to 50 microns

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