The presentation describes some of the malfunctions in a Power Plant. Many more can be simulated and operators told to handle the situations in the simulator. The trippings of Generator, turbine, boilers and all auxiliaries can be simulated to get hands on practice on the simulator before operating the actual turbogenerator and boiler associated equipment.

1. THERMAL POWER PLANT
SIMULATOR
MAJOR MALFUNCTIONS
IN
OPERATION OF 210 MW UNIT
Manohar Tatwawadi
DIRECTOR, TOPS, PUNE
01-Nov-19 1Manohar Tatwawadi

2. TRIPPING OF ONE ID FAN
Tripping of any one ID Fan
Specific Causes:-
• Motor Protection acted
• Supply failure to feeding Bus
• Low Lub oil Pressure
• Low Oil Level Tripping of Pump
• High Bearing Temp of Motor/Fan Bearing because of
failure of cooling water supply.
• Fan Vibrations very High
01-Nov-19 2Manohar Tatwawadi

3. TRIPPING OF ONE ID FAN…….
Immediate Plant Response to Malfunction:-
• Tripping of one FD Fan
• Furnace Draft Positive & fluctuation
• Disturbance to Drum Level(Dropping)
• Tripped Fan Discharge Damper closes to start again
Expected Immediate Operation Action:-
• Stabilize furnace draft
• Stabilize Drum Level
Final Correction of Malfunction:-
• Start ID Fan and normalize Draft
01-Nov-19 3Manohar Tatwawadi

4. TRIPPING OF BOTH ID FANS
Specific Causes:-
• 6.6 KV Supply Failure
• Failure of cooling water supply to both motors
Immediate Plant Response to Malfunction:-
• Tripping of Turbine / Generator
• FD/PA/Mills Trip. (Unit Trip)
Expected Immediate Operation Action:-
(Common for all Trips)
• Prepare for Hot Rolling
• Check Vacuum system is ok and Start Starting oil pump
• Reset Turbine Trip Supervisory relay and Watch Turbine Expansion.
• Check Feed Pump, Maintain Drum Level
• Start one ID Fan as soon as possible. Start one FD Fan also
01-Nov-19 4Manohar Tatwawadi

5. TRIPPING OF BOTH ID FANS
• Maintain Purge Condition and complete Furnace Purging.
• Lightup Boiler and Bring HP/LP Bypass into service
• Match Boiler Outlet steam/turbine metal/ temperature.
• Roll the turbine to 3000 RPM
• Synchronise Generator to the grid
• Stop Starting Oil Pump
• Quickly start PA Fans/ Milling System and load generator to
maintain steam temperature
• Watch Differential Expansions of HPT/IPT/LPT
• All the time maintain Normal water level in the Boiler Drum.
Local Operator Actions:-
• Local operator from each section (Boiler, Turbine and Auxiliaries)
confirm their scope of the plant is ready for Restart.
01-Nov-19 5Manohar Tatwawadi

6. TRIPPING OF ONE FD FAN
Specific Causes:-
• Motor Protection acted
• Supply failure to feeding Bus
• Low Lub oil Pressure
• Low Oil Level Tripping of Pump
• High Bearing Temp of Motor/Fan Bearing because of
failure of cooling water supply.
• Fan Vibrations very High
01-Nov-19 6Manohar Tatwawadi

7. TRIPPING OF FD FAN
Immediate Plant Response to Malfunction:-
• Tripping of one FD Fan
• Furnace Draft to High Negative
• Disturbance in Combustion
• Disturbance to Drum Level
• Tripped Fan Discharge Damper closes to start again
Expected Immediate Operation Action:-
• Stabilize furnace draft
• Stabilize Drum Level
Final Correction of Malfunction:-
• Start FD Fan and normalize Draft
TRIPPING OF BOTH FD FANS:- Similar to Both ID Fan Trips
01-Nov-19 7Manohar Tatwawadi

8. TRIPPING OF P.A. FANS
Tripping of One P.A. Fan
Specific Causes:-
• Motor Protection acted
• Supply failure to feeding Bus
• Low Lub oil Pressure
• Low Oil Level Tripping of Pump
• High Bearing Temp of Motor/Fan Bearing because of failure of
cooling water supply.
• Fan Vibrations very High
Immediate Plant Response to Malfunction:-
• P.A. Header Pressure Falls
• Lower Mills trip out to maintain PA Header Pressure
01-Nov-19 8Manohar Tatwawadi

9. TRIPPING OF P.A. FANS
• Steam Pressure and Temperature start dropping
• Unstable Combustion
• Drum level falls.
Expected Immediate Operation Action:-
• Reduce Generator Load
• Maintain Drum Water Level
• Cut in Heavy Oil Guns to stabilize Flame /combustion.
• Load the working PA Fan to Max and try to maintain PA header
Pressure
• Stabilize Boiler Steam Temp. (Adjust burner tilt/Excess air flow)
Local Operator Action
Check Tripped P.A.Fan. Get ready for restart and confirm
01-Nov-19 9Manohar Tatwawadi

10. High Furnace Pressure
Specific causes
• ID fan failure (Tripping on Motor or fan
bearing Temp)
• Mal operation of regulating vanes
• Closing of dampers on the flue gas side
• Manholes in the flue gas track suddenly open
• ID fan/PA fan air out of control
• Falling of a huge clinker in the furnace.
01-Nov-19 10Manohar Tatwawadi

11. High Furnace Pressure
Plant Response
• If furnace pressure reaches +200mm Unit will Trip
• Possibilities of furnace explosion suspected
• Airheater may trip.
• Boiler Pressure will drop.
• Ignitors may trip causing associated problems
• Furnace water seal may break.
• Possibility of Unit tripping on Total Flame Failure
01-Nov-19 11Manohar Tatwawadi

12. High Furnace Pressure
Operator Actions
• Check whether any damper has closed
• If one ID trips reduce load and stabilise on one ID
Fan
• Cold and hot air entry to idle mills is closed
• Check Airheaters are rotating. Restart tripped
Airheater
• Check furnace sealing
• Check ID fan auto control.
01-Nov-19 12Manohar Tatwawadi

13. Furnace Pressure High
Local operator actions
• Check for open manholes and close them
• Check airheaters for rotation
• Check dampers to be open position on flue
gas side.
• Check physically the ID fan vane mechanism
links for shearing.
• Check furnace water seal overflow.
01-Nov-19 13Manohar Tatwawadi

14. Furnace Pressure Low
Specific causes
• ID fan auto control failure
• ID fan vane control mechanism failure causing
vanes to open wide
• Sudden load throw off.
• Sudden decrease in air input (FD fan failures)
Plant Response
• At -200mm Unit will Trip
• Too low furnace pressure may blowout flame
from working.
01-Nov-19 14Manohar Tatwawadi

15. Furnace Pressure Low…
• Ignitors / Oil guns may blow out flames from
working
• May cause unstable condition.
Operator Actions
• Switch ID Fan Control to manual and try to bring
normal parameters
• Check air flow – Correct if necessary
• Check ID fan vane mechanism
• Restart FD Fan if the fan has tripped
01-Nov-19 15Manohar Tatwawadi

16. Drum Level Low
Specific causes
• Tripping of one of the feed pumps
• Mal operation of feed regulation Valve AUTO /
BFP Scoop AUTO
• Sudden reduction of load
• Sudden tripping of one or more mills/oil burners
in operation.
• Sudden water tube failure in the furnace zone
• Inadvertent opening of Emergency Drum Drain.
01-Nov-19 16Manohar Tatwawadi

17. Drum Level Low
Plant Response
• Water Level Low indication/Alarm
• If the water level goes very low -180mm, boiler
will trip on Drum Level Very low.
• If the water level falls below the visible range in
the gauge glass may affect the flow throw
downcomers and may lead to water wall failure.
Operator Action
• See that the reserve feed pump starts on Auto
and picks up the load
01-Nov-19 17Manohar Tatwawadi

18. Drum Level Low
• Raise the feed flow of the running BFP if possible
by taking the feed pump scoop on Manual.
Caution- working BFP may trip on feed flow very
high.
• Try to reduce furnace load gradually by tripping
mills/burners
• If the boiler has tripped check that all mills /fuel
has also tripped
• Check feedflow recorders
• Trip the UNIT. (Don’t bypass the UNIT tripping on
“Drum Level Very Low”
01-Nov-19 18Manohar Tatwawadi

19. Drum level Low
Local Operator Actions
• Check Tripped Feed Pump, Feed water Auto
Controller, Scoop Controller Linkage
• Check Drum Drain,
• Check for any riser tube leakages
• Check for Economiser water tube leakage
01-Nov-19 19Manohar Tatwawadi

20. Drum Level High
• High Drum Level beyond the visible range of
gauge glass can damage superheaters, main
steam line and turbine.
• Turbine must trip on drum level very high
+200mm
Specific Causes
• Mal operation of Feed water controls
• Feed water Flow and steam flow are not
matching
• Sudden Increase in load
• Sudden increase in Firing Rate
01-Nov-19 20Manohar Tatwawadi

21. Drum Level High..
Plant Response
• Water Level High Indication / Alarm
• Superheater Temp may drop sharply at Extreame
High Level
• The turbogenerator must be tripped at +200mm
level high (Drum Level Very Very high signal).
Operator Actions
• Switch feed controls to manual and control the
level
01-Nov-19 21Manohar Tatwawadi

22. Drum Level High
• Open the drum emergency drains
• Open main steam line drains
• Try reducing the load for controlling the water
level. (If water is high because of upward load
surge)
• Trip the turbine if the water level goes beyond
the visible range of the gauge glass.(Approx
+200mm)
01-Nov-19 22Manohar Tatwawadi

23. Fall of Condenser Vacuum
Specific Causes
• Reduced pressure of Gland Steam
• Low PRDS Pressure
• High level in condenser
• Failure of CW Pumps
• Drain in vacuum system open to atmosphere/
passing
• Leakage of air to vacuum system
• Opening of vacuum Breaker Valve
• Increase in Exhaust hood Temp
01-Nov-19 23Manohar Tatwawadi

24. Fall of Condenser Vacuum
• Operator Actions
• Trip the unit at Vacuum below 540mm
• Maintain the APRDS Press and Temp.
• Check CW Pump flow
• Reduce Load and bring the third Ejector in Service
• Check vacuum breaker valve for proper closing
and its water sealing
• Check and maintain Hot well level to NORMAL.
01-Nov-19 24Manohar Tatwawadi

25. 01-Nov-19 25Manohar Tatwawadi