The document provides information on governing systems and common problems encountered. It discusses: 1. The key components of a governing system block diagram including pumps, valves, filters and overspeed testers. 2. Cleaning procedures and stroke check requirements for governing systems. 3. Parameters that should be followed including pressures, signals, valve lifts and temperatures. 4. Common governing problems like hunting, chattering, and sudden speed variations. 5. Case studies examining issues like improper servomotor assembly and a bent pilot valve spring causing load hunting.

2. Governing systemGoverning system
System preparationSystem preparation
Parameters to followParameters to follow

3. GOVENING SYSTEM BLOCK DIAGRAM
PUMP
MAIN SOLENOID
VALVE
DUPLEX FILTER
OST TESTER
TRIPPING
DEVICE
ESV
STARTING
DEVICE
I / H CONVERTOR
SERVOMOTOR
GOV.
VALVE
OS GOVERNOR

4. CLEANING OF THE SYSTEM
Oil flushing:
- servomotor pilot pistons to be removed.
-cleaning of oil lines in the console.
- ESV cleaning and assembly.

5. Governor stroke check up:
preconditions
steam system should be completely isolated.
No vacuum
by pass trips coming from PLC/ DCS
check the the control valve movements vis a vis actuator signals.

6. Parameters
• Governing oil pressure : 8-10 atg
• Trip oil pressure : 7 -9atg
• Sec Oil Pr. : 1.5atg-4.5 atg
• signal : 4MA-20MA
• Valve Lift : 0 mm-full scale
• Governing oil temp : 50-60 deg c
• Max & Min Extr signal thro’ Governor & compare with diagram

7. Start up diagram
• Typical example
critical speed
zone
Time in minutes
Speed
in
rpm
Idle speed
Idle speed

8. COMMON GOVERNING PROBLEMS
- Hunting.
-Chattering.
-sudden rise /fall in the speed/ load.
-spurious tripping due to trip oil pr very low.

9. CHATTERING:
- Oil temperature, de aeration
- Oil pressure fluctuation

10. Hunting of control valves
1. Sec oil pressure VS valve lift calibration.
2. Oil purity
3. Sluggishness of the moving parts.
4. Frequent changes in steam inlet parameters.
5. Damage of control valve cones.

11. 6. Tuning of electronic signals in case of electronic
Governor.
7.Programming of controllers as per start up curve /
extraction map / site conditions.
8. Problems of EHTC ( converters ).
9. Damage of Electronic components.
Hunting of control valves

12. Trip oil pressure very low trips
1.Mechanical problems with tripping device.
2.Tripping device lever radial and axial clearances not proper.
3.Turbine axial displacement very high (failure of T B).
4. Control oil pressure very low.
5. Heavy leakage through ESV drains due improper seating
of disk and cylinder.
6. Governing console duplex filter choking.
7.Choking of trip oil line.
8. Lube oil pump discharge pressure fluctuation.
9. Malfunctioning of trip oil pressure low- low switch.
10. Overspeed of turbine by pin actuation

13. SUDDEN RISE/ FALL IN SPEED/ LOAD
- control valves’ problems.
-servomotor pilot piston non rotation.

14. Control Valve Actuator

15. P
c
T
PILOT PISTON ASSEMBLY

16. Pilot piston top

17. Spurious tripping :
sudden drop in the trip oil pressure
malfunctioning of pressure switches
blocking of oil lines viz. Sec oil , power oil lines.
Lay out of the governing piping- should allow smooth
flow, should
posses less bends.
Loose connections, particularly at trip solenoid valves.

18. DO’S & DON’TS OF TURBINE
OPERATION (BEFORE START UP)
Do:
1. Check up the start of opening and full lift of the
servomotor.
2. WWG- ensure I/H converter manual knob is in min.
position.
3.Ensure the extraction valves are fully closed
before rolling.
4. . Check the operation of over-speed governor once
in 3 months.

19. DO’S & DON’TS OF TURBINE
DON’T….
1. Try to tune the servomotor while m/c in
operation.
2. Operate the m/c with the governor hunting.
3. Meddle with the manual knob of I/H converter
when m/c is in operation.
4. Raise the speed fast when MOP/ Governor
are taking over.

20. EMERGENCY STOP VALVE

21. OVERSPEED TRIP PIN ASSLY

22. CHANGEOVER VALVE FOR QCNRV

23. TRIP SOLENOID VALVE

24. Case study #1
FEED BACK ON CONTROL
VALVE SERVOMOTOR ASSLY

25. OBSERVATION:
• Speed raise immediately after opening
of Emergency Stop Valve
ANALYSIS
• Improper assembly of servomotor with
control valve lever
• Result in lift of valve cone

26. Preventive Action : Assly sequence to be followed

27. 1. Fix the dampers (horizontal & vertical)
2. Fix the assembly fixture (Clamping
Device)
3. De-link Lever jointing Head & Control
valve lever.
4. Gently push the lever towards the Control
valve
5. Fix a dial gauge on the lever bracket and
the dial pointer on the pin towards the
control valve center.
Preventive Action : Assly sequence to be followed

28. 6. Bring the power cylinder piston rod to the
top extreme position and hold it there.
7. With the help of the fixture, lift the control
valve lever by 1.5 and < 2 mm and hold
the position there.
8. Link the power cylinder piston and the
control valve lever head and lock the nut
of the lever jointing head.
Preventive Action : Assly sequence to be followed

29. HP GOVERNING VALVE ASSLY

30. Case study # 2
20 MW STG
PROBLEM:
EMERGENCY STOP VALVE NOT OPENING
DURING THE LOAD RUN TRIAL THOUGH IT WAS
NOT HAVING OPENING PROBLEM DURING NO
LOAD TRIAL.

31. ESV ASSEMBLY DRAWING

32. ESV REMOVED FROM THE POSITION WITH THE STRAINER

33. Scratch mark

34. Broken tack welding

35. DETACHED DISPENSER

36. RESOLUTION
1. Scratch mark removed by lapping.
2. The Piston was made free moving.
3. Dispenser tack weld in thee places in position
and fixed firmly.
4. ESV assembled and mounted back in position.
5. Opening of the ESV done from the remote (Control
Room)
and found satisfactory.
6. Load run trial of 20 MW STG completed successfully.

37. Problem:
Load hunting at various loads, but
not always. All of a sudden hunting
occurs at full load or even at partial
loads
Reasons:
pilot valve compression spring is
having lot of bent. (Refer Figure)
Action taken:
New compression spring supplied,
case study # 3

38. Sitapuram Power

39. PILOT VALVE ASSEMBLY

40. COMPRESSION SPRING LOCATION