ALARMS CUASES CONSEQUENCES AND ACTIONS (stage-1) P.KOTESWARA RAO, Dy.Supdt (Operation) * ARRANGED IN ALPHABETICAL ORDER * AIR PREHEATER
1. APH A/B STANDSTILL 1.APH A/B main and aux. Motor stopped and air motor failed to start 2.Air motor failure/ solenoid failure 3.Compressed air not available 4.Isolating valve of solenoid valve closed condition/ air valve closed. *1.Rapid fall in air temperature 2.Rapid rise in gas temperature 3. Possible deformation of rotor 4.Possible fouling of seals #1.Try to rotate APH periodically 2.Try to restore electric/ air motor 3.Close air / gas damper 4.Open interconnection valve 5.Run air motor through bypass of solenoid. 6.Stop FD fan 7.If nothing is possible, kill the fire before APH distortion & foul 2. APH A/B AIR/ GAS OUTLET TEMPERATURE HIGH 1.APH air outlet temperature high because of SCAPH passing 2.APH bypass open 3.Gas outlet temperature high because of poor heat absorption in APH/ choking in passage 4.Possible APH fire 5.Improper soot blowing 6.APH plugging 3. APH BEARING TEMPERATURE HIGH/ VERY HIGH (60 deg.c/ 65 deg.c) 1.Low oil level 2.CW flow low 3.Bearing damage 4.Air/ gas leakage on to bearing
4. AIR HEATER MAIN MOTOR TRIP A/B AND AUX. MOTOR RUNNING 1.Selection changed to aux.motor 2.Main motor tripped due to overload/single-phase preventer/ supply problem #Check for the cause.
5. AIR HEATER -A/B FIRE DETECTION 1.Oil burners improper burning/ oil carry over to APH 2.Improper APH soot blowing/ choking of APH 3.Foreign material inside the APH *APH air and flue gas temperature rise sharply *At local APH colour peels off and very hot to touch #1.Close air and gas dampers 2.Stop FD fan 3.Flood APH with water 4.Continue air heater rotation, at least with air motor till it is possible. 6 APH A/B MAIN AND AUX. MOTOR TRIP 1.Main motor tripped. Aux. Motor started and tripped. 2.Aux. motor started and tripped 3.Supply interruption *1.Hot air temperature drop 2.Flue gas temperature rise 3.If air motor fails to start, corresponding FD and ID will trip with 30 seconds time delay #1.See whether air motor started. If not try to start it. 2.Look for the reason why main and aux. Motor tripped and try to rectify
7. APH-A/B TEMPERATURE DETECTION COOLING WATER FLOW LOW 1.Due to line choking 2.Cooling water line leak.
AUXILIARY PRDS
8. APRDS CV OPERATION MISMATCH 1. Erroneous switching of torque monitor 2. Motor temperature too high 3. Position transmitter failure 4. Position transmitter second channel failure 9. APRDS CONTROL/MEASURING SYSTEM TROUBLE. 1. Measuring system faulty à a) Flow meter b) Pressure Transmitter
Auxiliary steam Spray water
c) Temperature element 2. Position Transmitter faulty. 10. APRDS TRIP CLOSE VIA OSU 1. Down stream temperature high (300 ° C) 2. Control oil pressure /level too low (80 KSC)
3. Spray water pressure low (<80 KSC) 4. Oil pressure too high (170 KSC) 5. Contactor switching error 6. Pump Main supply failed or Pump temperature too high 7. Pump running time too long or oil temperature too high (OSU PUMP ON 120 KSC, OFF 160 KSC) 11. APRDS POWER/ FAN SUPPLY FAULTY 1. Power contact/ switching error 2. Fuse came out/ blown 3. Cabinet supply lost/ failed 12. APRDS DOWN STREAM TEMPERATURE HIGH (Normal 210 ° C, High 270 ° C)
1. Spray water not available. 2. Spray water-isolating valves at 10 m elevation in closed condition. 3. Spray regulating valve maloperation
13. APRDS OIL SUPPLY PRESSURE VERY LOW 1. Normal 120-160 KSC 2. Low <80 bar 3. Pump Main supply failed or pump temperature too high 4. Pump running time too long or oil temperature too high 5. Oil level low 14. AUXILIARY STEAM HEADER PRESSURE LOW 1. APRDS malfunction 2. MS pressure inadequate 3. Excess station consumption 4. Inlet/ Outlet valve closed 5. If fed from other units TIE valve closed 6. Pressure transmitter faulty (CLOSE EJECTOR INTERCONNECTION FROM OTHER UNITS. OBSERVE EJECTOR PERFORMANCE. IF HFO GUNS IN SERVICE CHANGES OVER TO LFO) ARCW PUMP
15. ARCW PUMP SUCTION PRESSURE LOW (OPERATING (OPERATING PRESSURE 1.5 KSC, LOLO 0.7 KSC) 1. One or more CW pump tripping 2. Inadvertent closing of suction valve. (RUNNING ARCW PUMP TRIPS AND STANBY PUMP ALSO DOES NOT COME IN TO SERVICE)
16. ARCW HEADER PRESSURE LOW (OPERATING PRESSURE PRESSURE 5.0 KSC, LOW 3.5 KSC)
1. Suction/discharge valve closed 2. Suction/ discharge valve seat fallen 3. One or more CW pump tripped 4. DOR reverse 5. Discharge flange/ line leakage 6. NRV not opening (STANDBY PUMP STARTS AT 4.0 KSC, IF SUCTION PRESSURE IS OK >0.8 KSC) • While starting the pump from local give close command in UCB to make the interlock work.
17. ARCW PUMP TRIP 1. EPB pressed 2. Suction pressure low low 3. CW pump trip or pressure switch malfunction 4. Electrical protection a) Overload b) Single Phase preventer c) Motor burnt d) Control circuit faulty e) Fuse blown f) Power cable got shorted 18. ARCW PUMP AUTO START FAILURE 1. Running pump tripped/ Discharge pressure < 4 KSC and suction pressure <0.8 KSC 2. Supply problem 3. Interlock problem 19. AUTO MANUAL TRANSFER OF ACS ACS CONTROL STATION . Hot well level CV, D/A level CV, ID fans vanes, FRS, BFP master, when came out of auto, this alarm Appears. It comes when the error becomes too large. (Difference between actual and set value) #Verify the cause and put it on auto. BFP 20. BFP SUCTION PRESSURE LOW. Low: 10 KSC Low Low: 7 KSC 1. Extraction pressure low 2. Deaerator level low 1000 MMWC 3. Deaerator minimum pressure control valve maloperation 4. Booster pump coupling broken. •
BFP trips on Low Low • Unit trips on Loss of all BFPs # Open F055/ F019 and maintain Deaerator pressure.
21. BFP cooling water flow low (<200 Lit/Min) 1. ARCW pump trips / Discharge pressure low 2. Interconnection clarified closed.
ALL BFP s TRIPPED 22. ALL 1. Electrical supply lost. 2. Suction pressure loss (Very Low- Not connected) a) actual b) Transmitter Malfunction 3. Deaerator level low (480 MMWC) 4. FRS malfunction –High BFP discharge 5. Running Pumps tripped. Standby pump not started. • Unit trip # If Unit doesn’t trip, trip the unit. 23. BFP DISCHARGE TEMPERATURE HIGH HIGH (236 ° C) 1. Temperature Element faulty 2. Churning (Recirculation valve not opening, Manual valve not opening, NRV not opening) • Pump gets damaged # Trip the pump if flow cannot be established.
24. BFP FLOW LOW LOW (50 T/Hr) 1. BFP scoop failed. 2. NRV not opening / Discharge valve seat fallen. 3. Discharge valve got closed inadvertently. 4. Flow transmitter failed. 5. BFP got unloaded due to internal pump problem. 6. Suction strainer clogged. 7. Air pocket in suction line. * Drum level comes down. * Load may have to be reduced. # Find the cause and try to rectify. # Or else immediately start the standby BFP and normalize the feed water flow keeping an Eye on the Drum level. 25. BFP AUTO START FAILURE 1. One of the permissive may be absent. a) Suction valve open (Bypassed in all the Units). b) Brg. Temp normal (<75). c) Lube Oil pressure normal (>1 KSC). d) Suction pressure normal (>10KSC). e) Lube Oil CW pressure normal (>2KSC). f) Recirculation valve open. 2. Selection not in LEAD/LAG as the case may be. 3. EPB pressed condition (Not Reset). 4. Supply may not be available in that bus. 5. Brkr. not racked in / any other brkr. Problem like selection not in remote / any other relay not getting reset etc. * Drum level may drop and Unit may trip. # Load has to be reduced (Runback to 50 % load) # Look for the causes and attend it.
26. BFP TRIP 1. Lube Oil pressure Low (<0.5 KSC). 2. Working Oil temp. High (>75alarm, 130 trip). 3. Thrust Brg. temp Hi-Hi (> 90 deg C). 4. D/A level Lo-Lo (480mm). 5. Balancing Leak off pressure Hi (25 KSC). 6. Axial shift High. 7. Suction to Discharge diff temp High (15 deg C). 8. EPB pressed. 9. 6.6KV Bus dead. * Drum level goes down and unit may trip on Drum level lo-lo. # Reduce load to maintain the Drum level. # Start the standby pump and restore the Drum level. # Find out the cause and rectify it. 27. BFP BRG. VIBRN. HIGH (8mm/sec pk to pk) 1. Misalignment 2. Insecure foundation 3. Oil flow/pressure adequate 4. Foreign particles in impeller 5. Bearing seizure 6. Very less flow through pump * Verify for reasons #1.Maintain comfortable flow (not too low or too high) 2.Inform conditioning monitoring to check 3. If trend is high side, trip the pump, and accordingly see that second pump has taken start. If not, Reduce load and maintain drum level. 28. BFP DISCHARGE HAEDER PRESSURE LOW 1.NRV closure/discharge valve closure 2.Scoop failure 3.FRS valve suddenly gets full open. 4.Pump impeller key got sheared off 5.Suction strainer choked
(low-155ksc, low-low-120ksc)
*Pump can't pump water to drum where pressure is more #Try to improve the pressure, if not see that other pumps have taken load. See drum level. 29. BFP SUCTION PRESSURE LOW (low-10ksc, low-low-7ksc) 1.D/A level low 1000mm 2.Extraction steam N/A (extraction valve closed due to high-high level) 3.Suction valve in closed condition 4.Pressure transmitter faulty *1.BFP trip kept bypassed 2.Alarm appeared #1.See for the cause and rectify
2.If extraction steams N/A, change auxiliary steam or CRH steam by opening F019 or F055 respectively. Then open F043 keeping an eye on D/A pressure and level. 3. If D/A level is actually low, trip the pump at 468mm if the pump is not tripping in auto. 30. BFP MOTOR O/L
(high-340amps, high-high-432 amps)
1.Mechanical defect, bending shaft, rotor rubbing against cabins, seizure of any bearing. 2.Lub oil pressure /flow low to a bearing coming its seizure. 3.Very high flow #1.Reduce flow 2.See for cause and get it rectified. 31. BFP LUB OIL PRESSURE LOW (low-1ksc) 1.MOP/AOP not developing pressure/ major oil leak from lube oil line 2.AOP power supply off/made off 3.Oil level in the sump very low. *Pump trips on protection at 0.5ksc #See for the reason and improve the lube oil pressure. 32. BFP LUB OIL TEMP.BEFORE/AFTER COOLER HIGH
(55/95 deg.c) deg. c)
1.Less/no cooling water flow to coolers (ARCW pump trip) 2.Cooler choking 3.Oil level in scoop very low. *Bearing may seize/damage #Check for problem and attend. 33. BFP SUCTION TEMP.HIGH (200deg.c) CRH steam pegging is still continuing after unit in service #Change over to extraction 34. BFP SSUCTION STRAINER CLOGGED (DP-3.5mmwc) #Start the other pump or else maintain drum level by proper action. 35. BFP MECH.SEAL WATER TEMP. HIGH
(80 deg.c)
Seal water tube leakage and feed water entry into seal water/choking of cooler oil/ Choking of magnetic filter #Stop the pump after starting standby pump and change over the load. 36. BFP HYDRAULIC COUPLING LUB LUB OIL PRESSURE LOW (low-0.8ksc, low-low-0.5ksc) 1. W.O.pump problem 2. Leakage in cooler 3. Leakage in Working Oil line.
37. BFP BALANCING LEAKAGE LEAKAGE PRESSURE HIGH (25ksc) Balancing disc maloperation *1.Pump trip on pressure 2.Sudden pulling and dropping of load from from pump pump can make pressure pressure very high high Due to axial movement of rotor. 38. BFP LUB OIL FILTER CHOKED If lube oil filter is choked lube oil pressure will drop. #Change over the filter 39. BFP SHAFT DISPLACEMENTHIGH (not in service) 1.Balancing device maloperation 2.Thrust pad damage, needs replacement 40. BFP BEARING METAL TEMP.HIGH (75 deg.c) 1.Lub oil pressure/flow low 2.Seizure of bearings 3.Axial thrust more/-balancing disc not proper 4.Shaft alignment alignment problem probl em *At 90 deg.c of thrust bearing temperature, BFP will trip. #Check for lube oil flow low, the bearing, stop pump if required. #Balancing gap to be adjusted
41. BFP BEARING VIBRATION HIGH HIGH HIG H (high-8mm/sec, high-high-10mm/sec peak to peak) 1.NRV/discharge valve / recirculation valve not opening/operating 2.Pump mechanical damage 3.Bearing oil flow low/bearings damaged 4.Feed water flow very less in the pump 5.Vibration pickup failure *Bearing/pump may be damaged #Verify for the cause and rectify
42. BFP BEARING TEMPERATURE HIGH 1.Lub oil flow/pressure low 2.Coolers ineffective 3.CW flow less for cooler *At 75deg .c alarm will appear *At 90 deg. C will trip with a time delay of 5 seconds #When alarm appears, check for the same
#Change cooler if required 43. BFP DISCHARGE PRESSURE LOW (70ksc) 1. Scoop failed 2.Main pump / voith get decoupled. 3. One of the impeller got delinked. (Key sheared)
44. BFP HYDRAULIC COUPLING OIL TEMPERATURE HIGH (70/130 deg. C) 1.Cooler ineffective 2.CW flow to cooler less #. Check cooler lineup/CW flow #Stop the pump and inspect the cooler 45. RUNNING BFP DISCHARGE PRESSURE LOW-LOW (50ksc) 1.Scoop failed 2.Main pump / voith get decoupled 3. One of the impeller got delinked. (Key sheared) CEP
46. CEP TRIP 1. EPB pressed 2. Hot well level low low <150 mm 3. CEP discharge pressure low low <25 KSC for 30 Sec 4. CEP flow low 5. Suction valve open feedback gone. (Pump trips even if the suction valve is actually open.) 6. Bearing oil temperature high (90 ° C) •
#
Second pump starts if permissive are available a) Hot well level normal b) Bearing temperature O.K. c) Recirulation valve open/ second pump running and discharge pressure O.K. Start Start any any one one pum pump p with with dis disch char arge ge valv valvee clos closed ed and and rec recir ircu cula latio tion n pump pump ope open. n. Obs Observe erve vac vacuu uum. m.
47. CEP DISCHARGE HEADER PRESSURE LOW (ALARM 25 KSC) (Standby pump starts after 10 Sec time delay) 1. Frequency low 2. Hot well level CV malfunction 3. Pump shaft got sheared off 4. Discharge valve got closed 5. Deaerator high level control valve malfunction 6. Hot well level going up due to LP bypass opening or Blow Down Valve opening 48. CEP MOTOR OVERLOAD (80 Amps high, 96 Amps trip) 1. Too tight glands packing
2. Mechanical defect i.e., bending of shaft, rotor rubbing against casing 3. Bearing seizure 49. CEP AUTO START FAILURE 1. One or more permissives not available 2. Breaker not racked in or problem in breaker 3. DC supply problem 4. UCB selection not in auto 5. Local selector mode in switchgear mode (not in Remote mode) 50. CEP BEARING TEMPERATURE HIGH 1. Bearing oil level low/ contaminated 2. Shaft wobbling/bent/eccentrici wobbling/bent/eccentricity ty 3. Misalignment (Stop the pump at 90 ° C bearing temperature) 51. CEP TRIP 1 EPB 2 CEP discharge discharge pressure pressure low low (<25 KSC, 30 Sec) 1. Hot well level low low (<150mm) 2. Suction valve open feedback gone (The pump trips even if the suction valve is actually open) • Second pump starts if permissives are available. a) Hot well level normal b) Bearing temperature normal c) Recirculation valve open / Second pump running & discharge pressure O.K. # Start any one pump with discharge valve closed and recirculation valve open. Observe the Vacuum 52. CEP MOTOR BEARING TEMP. HIGH (70; HIHI 75) 1 Bearing oil level low/contaminated 2 Shaft wobbling/bent/eccentrici wobbling/bent/eccentricity ty 3 Misalignment *Bearing damage #Stop pump 53. CROW BAR IN OPERATION. Crow bar protection is used to protect rotor winding against over voltages, which are likely when generator falls out of step (out of synchronism) or transient over voltages comes in out of generator terminals. In such circumstances crowbar comes in to service and acts like a load on excitation system, suppressing the over voltage. 54. Charger trouble Rectifier fuse fail In put AC fail Out put Dc Fail
55. FAILURE OF AUTO CHANGEOVER FROM AUTO TO MANUAL. When AVR auto fails due to any reason control should change over to manual
CRT 56. CRT LEVEL HIGH (2500MM) 1 Maloperation of CRT level C.V 2 Maloperation of D/A hi level C.V F571 *CRT overflow. DM water wastage
57. CRT LEVEL LOW. (750 MMWC) 1. DM Makeup pump tripped 2. CRT level CV malfunction 3. Drain valve inadvertent opening 4. Make up very high due to CBD, PRDS, or Tube leakage. • •
Gland seal water may be lost No make up to condenser.
58. CONTROL AIR PRESSURE LOW (2.5 ksc, operating pressure 5ksc) 1.C.A compressor tripped 2.Leakage in control airline *Pneumatic valves may fail/ close / open as per normally closed/ open or stall out #Look for FRS valve position, all trip valves, and extraction valves Fail-safe, Stay put-lock up relay. Valves /dampers operation affected with loss of CA. 1. HFO trip valve close 2. LFO trip valve close 3. Igniter trip valve close 4. RH block valve close 5. Seal air discharge discharge damper rema remain in as as it is is 6. Pf valve remain as it is (But due to gravity it may get closed) 7.Guns power cylinder remain as it is 8. Igni Ignite terr powe powerr cyli cylind nder er remain as as it it is is 9. HFO PCV remain as it is 10.LFO PCV remain as it is 11. Igniter oil PCV remain as it is 12. Gas/ air dampers remain as it is 13. Interconnectio Interconnection n dampers dampers rema remain in as as it is is 14. FD IGV remain as it is 15. ID IGV remain as it is 16.F 6.FD dis disccharge rge da damper remain as as it it is is 17.ID .ID disc ischarge rge damper remain as it is 18.SH spray station close 19.RH spray station close 20.RH sp spray bl block va valve close 21.CAD/ HAD remain as it is 22.M 22.Mak akee up up con contr trol ol statio station n clos closee 23. 23. LPH LPH// HPH HPH norm normal al drip drip cont contro roll val valve ve clos closee 24. LPH/HPH Alternate drip CV open 24. BFP recirculation valves open 25.CEP recirculation valves open
26. Hot well level control valve close 27. FC NRVs open (if CRH pressure is OK) 28. BDV open 29. FRS remain as it is 30. De Deaerator High Level CV close 31. Deaerator pressure CV close 32. PA IGV remain as it is 33. SH S H/RH gas bypass dampers remain as it is 34. Seal steam diverting valve Open to condenser 35. Cl C linker grinders Close by gravity (If CA is lost during opening) 36. Ta Tampering air damper remain as it is 36. 36. HFO HFO sho short rt reci recirc rcul ulat atio ion/ n/ Long Long reci recirc rcul ulat atio ion n open open 37. AP APH gas inlet damper remain as it is 38. Soot Blowing CV Close 39. Extraction line drains open 40. Ventilation valve open 41. HFO pressurising pump house R/C open 42. Deaerator CRH (55) block valve. Close 43. Deaerator over flow Open 44. CRT level CV Open 45. Daerator pressure CV remain as it is # Reduce CBD, APRDS Fill CRT with bypass valve Close make up to condenser. Start additional Make Up pump.
59. ANY CW PUMP AUTO TRIP 1.Lub water pressure low 2.Pump discharge pressure high/ discharge valve closed 3.Overload #1.Reduce load if vacuum affected 2.Talk to offsite engineer /Unit-1 engineer for CW pump position 3.Try to restore back the CW pump, otherwise reduce load so as to maintain vacuum.
DEAERATOR
60. DEAERATOR LEVEL LOW (NORMAL 2600, LOW 1000, LOW LOW 480) 1. CEP tripped /low CEP discharge/ CEP faulty operation. 2. Drain valve passing or inadvertent opening 3. BFP drain passing or inadvertent opening 4. D/A level CV malfunction 5. DM makeup pump trip 6. CEP recirculation opened full in full load condition
7. Too much drainage from the boiler/ long tube leakage/major feed water line leakage *BFP trips at low low 480 mm 61. DEAERATOR LEVEL HIGH (NORMAL 2600,HIGH 2950,HIGH HIGH 3050) 1. High CEP discharge 2. Malfunction of D/A level CV 3. Malfunction of Makeup valve 4. BFP tripped, Voith failed 5. Malfunction of hot well level CV •
Extraction block valve closes at high high 3050 • Possibility of water entry in to turbine increases • Heavy hammering in D/A • Overflow line opens # Reduce condensate flow to deaerator and direct to CRT Open drain / overflow if required Reduce hot well level make up 62. DEAERATOR PRESSURE HIGH (NORMAL 11-12 KSC, HIGH 16 KSC) D/A minimum pressure control valve maloperation Aux/CRH steam pressure high *Safety valve lifts # Reduce D/A pressure Close F019/F055 valves 63. DAS TROUBLE
Any one processor halted. 1. Loss of supply 2. Card problem DOSING
64. HP DOZING SYSTEM TROUBLE 1. Dosing tank level low 2. Preparation tank level low 3. Dosing pump motor tripped a. Motor overload b. Single phase preventer c. Motor got burnt 4. Discharge pressure low.
65.
LP DOSING PUMP DISCHARGE PRESSURE LOW (5ksc) 1.Shear pin broken 2.Suction filter choked 3.Motor not running 4.D/A pressure low
5. Dosing tank level low 6. Preparation tank level low 7. Dosing pump motor tripped a. Motor overload b. Single phase preventer c. Motor got burnt 8. Discharge pressure low.
66. HP DOSING PUMP DISCHARGE PRESSURE LOW (160 ksc) ksc) 1. 2. 3. 4.
Motor not running Discharge valve closed Pump stroke minimum Stroke shear pin got sheared.
66. HP DOZING SYSTEM TANKS LEVEL TROUBLE 1.Preparation tank level low 2.Dozing tank level high/ low
67. LP DOSING SYSTEM TROUBLE 1) 2) 3) 4)
Pump motor tripped etc Dosing tank level low Preparation tank level low Dosing pump motor tripped a. Motor overload b. Single phase preventer c. Motor got burnt 5) Discharge pressure low.
68. LP DOSING SYSTEM TANKS LEVEL TROUBLE 1.Metering tank level low 2.Preparation tank level low #Make up the tank levels
69. UNIT DC SYSTEM E/ F *E/ F in DC system a. Earthling in field devices b. Earthling in DC equipment i. Solenoids
ii. Motors iii. Chargers c. Earthling in Bus d. Earthling in Cable # Observe DC voltage • Faulty pick up of relays may be there. ESP
70. PARTICLE EMISSION RATE HIGH 1.ESP field failure/ performance poor 2.ESP auxiliary failure (rapping) 3.Less retentivity/ reactivity of coal 4.Poor combustion/high ash level in hoppers 5.Very high air flow /charge ratio is not proper 71. ESP TROUBLE 1.Power supply failure in one or more passes 2.Flushing fan failure in one or more passes 3.ESP failure due to failure in controls/ transformers/ rectifiers etc 4.Shorting/ snapping of electrodes/ dislocation of electrodes etc 5.ESP fields tripped on low voltage 72. ESP RAPPING MECHANISM TROUBLE 1.Emitter/collector rapping motor failed due to overload or single-phase preventor. 2.Supply problem 1 ration of D/A Hi level C.V571 *CEP trips on lo lo LPBP if in service gets trip closed # If it is not possible to restart CEP (Try keeping an eye on D/A level), trip the unit 73. ESP RECTIFORMER (415 V to 80 KV Transformation, then rectification through diodes) TROUBLE One of the rectiformer failures Oil le81. FD FAN BEARING VIBRATION TROUBLE (high-8mm/sec, high-high -10mm/sec, peak to peak) 1.Fan impeller or IGV damaged 2.Oil level low/ nil in bearing 3.No CW flow to bearings, so bearing got damaged 4.Mis alignment *Bearing may get damaged and seized #1.Check for the cause and rectify it 2.If vibrations are in rising trend and maintaining high value, trip the fan
74. EXHAUST HOOD TEMPERATURE HIGH 1.A thermostatic alarm switch, located in the turbine exhaust hood, closes its contacts when the Temperature of the steam from the last stage turbine wheel exceeds 80 deg.c and is wired to an alarm #Apply spray water. Excessive use of spray may cause unnecessary erosion of the long last stage Buckets. *Clearances may be affected LPT last stage blades *During start up and low load operation, when the turbine stages remove only little energy from the Steam, the exhaust steam energy at a temperature that is too high for the last stages and the exhaust Hood
75. EXTRACTION AIR RELAY DUMP VALVE When the turbine trips, the dump valve spring is actuated to cut off the air supply to the NRVs. The Existing air in the NRV cylinder is discharged to atmosphere and this results in NRV being force closed. This is to provide adequate over speed protection by closing of NRVs in extraction lines Also whenever extraction relay dump valve is actuated, the air signal it provides to the blow-down Tank will be interrupted and exhausted, thereby opening the blow down valve.
76. FIELD BKR NOT AVAILABLE Closing coil supply failed Tripping coil supply failed.
77. TRIP FOR BOTH FANS NOT AVAILABLE. When generator is in service with excitation ‘ON’ failure of both fans for more than 15 second will generate class-A trip through Excitation system fault-A in GRP. FD FAN
78. FD FAN MOTOR BEARING TEMPERATURE HIGH (high-70deg.c, high-high-75deg.c) 1.Oil level in the bearing low/ contaminated 2.Spurious alarm *Bearing may get damaged and seized #Reduce load on the fan, check oil level and quality. Get it topped up and restore load
79. FD FAN MOTOR OVERLOAD 1.Too high airflow 2.Impeller fouling with foreign material 3.Bearing seizure
*FD fan may trip Reduce FD load immediately and see that alarm gets reset a. vel low b. Oil / winding temperature high c. Buchholtz operated d. Diodes failed (result in high oil/wdg temperature) *Field gets off #1.Call ESP operator & confirm from which pass and which field it is coming 2.Inform E/M to restore the field 80. FD FAN TRIP 1.EPB pressed 2.Corresponding ID fan tripped (when both FDs in service) 3.If both Ids tripped 4.Corresponding APH tripped, 30 minutes time delay 5.Electrical problem (O/L, E/F etc) 6.Supply dead *1.Air flow comes down 2.Combustion disturbance 3.Disturbance in furnace draft 4.Disturbance in drum level #1.Trip one top mill (preferably D or E, top mill) 2. Stabilise furnace 3. Take oil guns preferably in lower mills 4.Check for closing of air and gas dampers of corresponding APH and closing of FD fan discharge Damper 5.Stabilise drum level 6.Reduce load in generator 7.Load running FD fan to maximum as possible and regulate fuel as per requirement 8.Maintain steam pressure and temperature 9.Watch turbine differential expansions if steam temperature comes down 10.If tripped due to electrical protection, inform E/M 11.Check for the cause and try to restore.
81. MILL FEEDER TRIPPED
1.Motor control trouble
a. Motor speed less than 60 rpm b. Overload for 30 seconds c. Input phase loss d. Gross motor speed deviation >200 rpm e. Momentary power loss > 200 seconds f. No coal from bunker
g. No coal delivery h. Discharge chute plugged *1.Load comes down 2.Mill trips on emptying 3 to 4 minutes time delay (<5minutes) #Check for the cause and act accordingly. If everything is found OK, try taking feeder into service, After cutting guns.
82. MILL FEEDER UNDERWEIGHT/ OVERWEIGHT Feeder is calibrated to deliver 110 kg per turn of head pulley. For adjusting this if the leveler bar is Driven higher and higher, at 229 mm of bed thickness it stops and if its driven lower it stops at 127 mm of bed thickness #For overweight reduce speed, inspect for line releasing stuck up #For underweight increase speed, check up foreign materials
83. MILL FEEDER CLEAN OUT CONVEYOR STOP 1.Due to foreign material / coal spillage load on shear pin high and sheared off 2.Clean out conveyor ge ge arbox defective 3.Clean out conveyor motor tripped 84. MILL FEEDER BELT STOPPED 1.Coupling between motor and gear box sheared 2.Belt got cut 3.Pulley damaged *1.Load will come down 2.Mill outlet temperature rises #1.If it confirmed that feeder belt has snapped, stop the feeder motor 2.Shut down the milling system 3.Take standby milling system into service if available 4.Inform to R/M for inspection 85. MILL FEEDER COAL SUPPLY LOSS 1.Upper see coal 2.Lower see coal 3.Bunker empty 4.Coal jamming at chute 5.Malfunction
86. MILL FEEDER OUTLET CHUTE PLUGGED
1.Wet slurry coal 2.Foreign material at chute *Feeder trips/ mill outlet temperature shoots up #Stop the milling system and take standby mill in service
87. MILL FEEDER TROUBLE 1.Overweight/ underweight 2.Clean out conveyor stopped #1.If it is due to under weight raise speed and for over weight reduce speed 2.If clean out conveyor stopped, shear pin might have got sheared off. Ask R/M to attend it 88. GRAVIMETRIC FEEDER TEMPERATURE HIGH Fire inside the feeder *Belt and C&I cabinet may get damaged #1.Trip the feeder and stop the milling system 2.Close bunker gate 3.Close isolating damper 4.Open the firewater into the feeder 5.Get the front door opened through R/M 6.Inspect whether fire is extinguished or not/ remove the coal and clean the feeder 89. FUEL / AIR FLOW DIFFERENCE DIFFERENCE HIGH, VERY HIGH There is a set curve for different coal flow in ACS for FD vane in auto with oxygen as trimming (Convection factor). If the deviation from the set curve (value) is high/ high high this alarm appears #Check for sudden rise/ drop in coal flows and air flow and restore the deviation to minimum
90. FLUE GAS PERCENT OXYGEN HIGH/LOW LOW 1.Air flow less 2.Coal flow more 3.Airflow reduction may be due to FD blade-pitch control problem/ damper vane closing 4.Rise in airflow due to CMC 5.Feeder overweight *1.Incomplete combustion 2.High bottom ash/ fly ash, unburnt carbon % HIGH 1.High excess air due to sudden vane opening 2.Coal flow less
*High exhaust losses cause and flame instability #Adjust air and coal flow so that oxygen is maintained 91. MAXIMUM/ MINIMUM FIELD INTERVENTION Max. Filed current above 1326 Amps may damage the rotor winding. So over excitation limiter intervenes whenever the machine loading (MW& MVAR) is beyond its capability and brings down the excitation, thereby keeping the machine within its thermal capability. But this limiter intervenes after a certain delay so as to permit temporary over excitation. Limiters do not impair the control behavior of the AVR as over excited condition can exist in the event of a load raise or because of short time faults in the power supply networks. The AVR reacts to a distant fault and applies ceiling excitation (to the tune of twice full load excitation. limited to a few seconds), thereby increasing the synchronizing torque of the machine and prevents it formloosing synchronism. How ever if the fault persists and not been cleared by a set time, delayed rotor current limiter comes into operation preventing the Generator and excitation system from damage. This limiter intervention level also get affected by the position of a switch in UCB Generator panel which decides the capability limits for the generator depending up on generator casing hydrogen pressure. Min. Field current below 129 Amps may result in Overheating in stator end winding.
During under excitation rotor field is very weak and it normally happens when the machine is operating in leading MVAR region i.e., when the system is lightly loaded. Under this condition of reactive power absorption the rotor end windings are thermally stressed.
HEATERS
92. HP HEATER (5 /6) LEVEL HIGH/ LOW (HIGH-500, HIGH-HIGH-860, LOW- 200) 1.Failure of drip control valve operation 2.Inadequate extraction pressure 3.Tube failure *At High-High level extraction block valve will close and heater gets bypassed #1.Take the control into manual and try to maintain level 2.If not possible, bypass the heater and take it out of service 93. LP Heater 2/3 LEVEL LOW/ HIGH/ VERY HIGH (87/ 196/ 296) 1.Drip CV malfunctioning 2.Tube leakage 3.Extraction pressure low *At very high-level heater extraction block valve gets closed and heater gets bypassed
94. LP Heater- 1 LEVEL LOW/ HIGH / VERY VERY HIGH (187/ 296/ 55) Maintain with the alternate bypass valve.
HYDROGEN
95. COLD H2 TEMPERATURE HIGH CE/ OCE 1.Cooler got choked 2.Cooler clarified water flow reduced/ low 96. GENERATOR H2 SUPPLY PRESSURE PRESSURE LOW/ HIGH (HIGH-2.2ksc, LOW-0.22ksc) After the regulator pressure in filling rack high/ low Regulator not working. H2 Cylinder got emptied.
97. H2 PURITY LOW IN GENERATOR CASING (<92%) 1.Drier not operating properly 2.H2 cylinders purity low 3.H2 Cooler leakage 4.Vacuum pump not in service 98. GENERATOR CASING COLD HYDROGEN TEMPERATURE HIGH (60 EDG.C) No clarified water flow At 65 deg.c generator will trip
99. INTERVENTION MAXIMUM TEMPERATURE COLD H2 TURBINE TRIP (65 deg.c) Cold gas temperature high alarm appears at 60 Deg C. Look for proper opening of Hydrogen cooling control valve. If required operate bypass valve. Loss of control supply to the card or power supply to the motor may also cause this.
100. LIQUID IN GENERATOR CASING 1.Seal oil leakage to H2 side 2.H2 coolers leakage #Close one by one cooler and determine which cooler has leakage HOTWELL
101. HOTWELL LEVEL LOW Normal Normal:: 460 low: low: 310 low low: low: 150 MMWC MMWC 2 Maloperation of condenser make up valve 556/557 3 Too high CEP flow/maloperation of hot well C.V 554 Maloperation.
102. HOTWELL LEVEL HIGH Hi-650 MMWC High High-750 MMWC 1. Maloperation of condenser make up valve (F556, F557) 2. Maloperation of Hot well level C.V. 3. LPBypass opened. 4. CEP not delivering properly. • Vacuum drops • LPBP gets trip close at High High (730 MMWC)
103 . ISLANDING OPERATION: The station survives with some predetermined load in grid feeder mode (Part-grid), islanding itself from the rest of the grid. HOUSE LOAD: Station survives as a separate entity just feeding its own auxiliaries. 46 Hz
à
2 sec Time delay
à
TRIP ALL FEEDERS 45 Hz
à
instantaneous
à
ID FAN
104. ID FAN MOTOR BEARING TEMPERATURE TEMPERATURE HIGH (high-70 deg.c, high-high-85deg.c) 1.Oil level in bearing low 2.Oil contaminated 3.Misalignment *Bearing may get damaged #1.Check for oil level and get it topped up. 2.Check oil if contaminated
105. ID FAN TRIP 1.EPB pressed 2.Scoop oil pressure low (0.24ksc with a time delay of 3 minutes) 3.Scoop oil temperature high (130deg.c) 4.Both APH tripped 5.Electrical protection, O/L, E/F, flashover, etc 6.Supply dead *1.Corresponding FD fan trips 2.Furnace gets pressurized 3.Combustion disturbance 4.Disturbance to water level in drum 5.FD fan discharge damper, APH inlet/outlet damper closed
#1. Trip one top mill preferably DE if 5 mills are in service and reduce coal flow 2. Stabilize furnace draft 3. Stabilise drum level 4. Take oil guns preferably in lower mills 5. Reduce load on generator 6. Adjust airflow with running FD fan 7. Observe wind box pressure 8. Stabilise combustion and unit load at coal flow at which one FD fan can give enough excess air 2.5%(at least) 9 Check furnace flame condition and can remove oil support 10. Check for the cause of ID tripping and try to restore it 11 .If it tripped due to electrical cause refer to E/M
106. ID FAN HYDRAULIC COUPLING OILPRESSURE LOW (low-0.3ksc, low-low- 0.24ksc) 1.Working oil pump not discharging properly 2.Filter got choked *1.Fan will trip if pressure drops to 0.24ksc with 3 minutes time delay 2.Hydraulic oil temperature may rise #Change the filter and check for improvement in pressure 107. ID FAN MOTOR OVERLOAD (appear at 132 amps) 1.Bearings seized/ fan reverse rotation 2.Impeller fouling / foreign material inside *ID fan may trip on O/L #1.Reduce ID fan load and check for alarm resetting 2.Reduce unit load if required 108. ID FAN HYDRAULIC C COUPLING OUPLING OIL TEMPERATURE TEMPERATURE HIGH (80 deg.c) 1.Running at lower scoop position for longer time 2.Low oil lID FAN BEARING VIBRATION TROUBLE TROUBLE (8/10 mm/sec peak to peak) 1.Inboard/outboard bearing vibration high 2.Oil level in the bearing low/ contaminated 3.Bearing damaged 4.Impeller fouling 5.Signal lost 6.Misalignment 7.Oil flow less due to filter choked *Bearing may get damaged and seized #Reduce load on the fan, check check for the cause oil level and quality from local. Get it topped topped up and Restore load level 3.Low CW flow/pressure
*ID will trip at 130 deg.c #1.Increase scoop 2.Check for oil level and pressure
109. ID FAN HYDRAULIC COUPLING OIL LEVEL LOW 1Oil leakages/ level switch malfunction *Scoop oil pressure may come down and temperature may rise #Get the oil topped up 110. ID FAN HYDRAULIC COUPLING COOLING WATER FLOW LOW 1.Water is not available/ clarified pump trip/ cooler choked/ cooler valve closed inadvertently *Hydraulic oil temperature may rise #Check for the CW availability if not restore 111. ID FAN SCOOP OIL PRESSURE LOW 1.Working oil pump not discharging properly/ failed 2.Filter got choked 3.Working oil level very low *1.Fan will trip if pressure drops to 0.28ksc with 3 minutes time delay #Change the filter, oil level, its condition etc and check for improvement in pressure MILL
112. MILL MOTOR OVERLOAD (32.4 amps trip) 1.Foreign material in the mill 2.Too much coal flow 3.Mill outlet is blocked 4.Primary air flow drop out 5.Ball and race broken #1.Do not take local run without informing E/M 2.Reduce coal feeding to minimum 3.If needed cut out feeder after taking oil support 4.Stop the mill and inspect, remove foreign material
113. MILL OUTLET TEMPERATURE HIGH (100 DEG.C) 1.Fire in mill 2.Mill is emptied 3.Low coal feeding and high airflow 4.HAD full open and CAD not opening
*1.It is not advisable to run the mill at higher temperature as it may damage the total mill 2.Explosion can occur #1.Reduce the mill outlet temperature by opening cold air and giving more coal feed 2.If it is due to fire in mill, dump coal and minimise hot air flow 3.Trip milling system and close isolating damper and PF valves 114. MILL DP LOW/ HIGH (low-250 mmwc, high-750 high-750 mmwc) a. LOW 1.Low coal feeding 2.Worn out throat gap or air regulating ring due to chute jamming 3.Very less recirculation *1.Chance of coarse coal particles entering the furnace is high 2.Fineness may come down/ PF valve closed/ pipe choking b. HIGH 1.High coal feeding 2.Throat gap/ air regulating ring choked/ blocked 3.Very high recirculation *More load on mill #Take measures to get DP between 400-600 MMWC .If not stop the mill and inform R/M for checks 115. MILL NITROGEN PRESSURE LOW/ VERY LOW (low-26ksc, low-low-18ksc) 1.Leakage in nitrogen system 2.Drop in oil pressure due to leakage 3.Maloperation of loading pump *At low-low mill trips #1.Immediately charge nitrogen 2.Pump oil in the loading system
116. MILL LUB OIL PRESSURE VERY LOW (low-0.8ksc, low-low-0.5ksc) 1. Pump not discharging properly/ failed 2.Filter got choked 3.Gearbox oil level very low *1.Mill will trip if pressure drops to 0.5ksc with 10 minutes time delay #1.Change the filter, oil level, its condition etc and check for improvement in pressure 2.If improvement cannot be improved trip the system 117. MILL LUB OIL FLOW VERY LOW
Comes from flow switch
118. MILL LUB OIL PUMP TRIP 1.Breaker closed in test position 2.Actually lube oil pump tripped a. Motor over load b. Single phase preventer c. Motor burnt d. EPB pressed *If lube oil pump trips, within 10 seconds mill also will trip #If lube oil pump tripped and mill did not trip, trip the milling system 119. MFT 1.Furnace pressure high/ low + or - 200mmwc 2.Boiler drum level high/ low + or- 250mm (time delay 5 sec) 3.Loss of both ID and FD fans 4. Loss of both BFPs 5. Loss of both APHs 6. Loss of all flame. 7.All fuel loss 8.Airflow <30% 9.Reheater protection (unit protection) ESVs & IVs closed, boiler load >60%, at least one set of HPLP bypass failed to open #1.Check for the cause 2.Do furnace purging to relight up 120. Aux oil Pump (AOP)IN SERVICE When lube oil pressure low and MOP discharge low-12.2ksc/sceonds
121. TG Oil Pump (TGOP)IN SERVICE (discharge pressure-8.75ksc) pressure-8.75k sc) 1. Abnormal stoppage of AOP due to mechanical fault 2. Thermal overload in motor motor 3. Supply problem. 122 . Emergency Oil pump (EOP) IN SERVICE (discharge pressure-1.6ksc) Abnormal stoppage of TGOP due to mechanical fault, thermal overload in motor But EOP will not stop in case of thermal overload, but alarms comes
123 . PA FAN BEARING TEMPERATURE HIGH (high-65deg.c, high-high-70 deg.c) deg. c) 1.Lub oil level low/ nil in bearing/ FLOP tripped 2.No CW flow to bearings, so bearing got damaged
3.Misalignment 4. Unbalance. **Bearing may get damaged and seized #1.Check for the cause and rectify it 2.If temperature is in rising trend and maintaining high value, trip the fan
124. PA FAN MOTOR OVERLOAD 1.Too high airflow 2.Impeller fouling with foreign material 3. Locked rotor due to bearing seizure 4.Discharge bellow leaking 5.PF valve not opened 6.Inlet vanes are in open condition while starting *PA fan may trip #1.Reduce. PA air flow immediately and see that alarm get reset 2.While starting see that vanes are closed, PF valves closed, fluid coupling is OK
125. PA FAN BEARING VIBRATION HIGH (high-8mm/sec, high-high-10mm/sec)
1.Lub oil level low/ nil in bearing/ FLOP tripped 2.No CW flow to bearings, so bearing got damaged 3.Misalignmen
126. PF BURNER TROUBLE 1.When > two scanners sense no flame 2.Air regulator of running mill closed 3.Impeller retracted 4.Coal available permissive gone 5.Feeder tripped 6.Nitrogen pressure/ lube oil pressure is low 7.PF valves open feedback gone for running system 8.Lub oil pump tripped 9.PF/ FO logic problem 10.CW flow to mill oil cooler low 11. Mill bearing oil temperature high #Look for the cause and inform C&I
127. RUNBACK IN OPERATION 1.Load is raised above capacity
2.Capacity lost due to loss of auxiliaries such as mills, ID fan, and FD fan, BFP, CEP etc
128. SCANNER AIR PRESSURE VERY LOW 1.Fan tripped and other fan discharge damper fails to open 2. Impeller disengaged from shaft 3.Heavy leakage in line *1.At 500-mmwc alarms appears 2.At 400 mmwc standby fan comes in auto 3.Scanner may sense no flame due to dust problem #See that all scanners are showing flame Clean the scanners, one after another
129. SEAL AIR FAN TRIP/ TROUBLE 1.On starting the fan if discharge damper is not opening with second command, this alarm appears #At local get the discharge valve opened 2. When one of the seal air fan tripped/ stopped.
130. SEAL AIR HEADER PRESSURE LOW (low-1000mmwc, low-low-900mmwc) 1.Seal air fan tripped/ trouble 2.Line puncture *Mills seals may not be effective If seal air header pressure cannot be improved, trip one/ two mills and close their seal air valves 2.Start the standby fan and stop the first seal air fan 3.Close the seal air valve of standby mills
131. SEAL OIL COOLERS COOLING WATER FLOW LOW 1.Isolating valve in the line closed 2.CW pressure/ flow dropped 132. H2/ SEAL OIL DP LOW (<0.3ksc) DPR is malfunctioning 133. SEAL OIL FILTER CHOKED DP> 0.8ksc Rotate the magnetic filter.
134. SEAL OIL DISCHARGE TANK LEVEL HIGH Float mal-operation. mal-operation. 135. SEAL OIL TANK VACUUM LOW (500mm Hg) 1.Seal oil pressure at turbine end high 2. Seal oil pressure at exciter end low 3. Seal oil tank vacuum low
136. MAIN AC SEAL OIL PUMP TRIP 1.Supply problem 2.Motor overload or single-phase preventer *If DC SOP fails to take start, hydrogen may escape to atmosphere #1.Start DC SOP locally if it not started 2.If DC SOP fails to take start see whether EOP or TGOP is running 3.With EOP/ TGOP in service maintain 1.4 ksc of hydrogen pressure in the generator 4.If no pump is running, purge out the hydrogen with CO2. 137. EMERGENCY DC SEALOIL PUMP RUNNING 1.Started from UCB 2.Took start in auto if so pressure drops to 5.6 ksc #Look for the cause and start AC SOP after resumption of power or rectification of pump problem 138. AC/ DC SEAL OIL PUMP OVER LOAD AC SOP trips on overload DC SOP remains in service even after overload alarms appears. Care should be taken to take out The cause of overload
139. EMERGENCY DC SEAL OIL PUMP UNHEALTHY 1.DC supply not available 2.Not in remote 140. SEAL OIL VACUUM TANK LEVE LEVEL L HIGH/ LOW (+ OR - 150) Maloperation of float. Seal oil leakage. 141. SEAL OIL PUMP TRIP 1.Supply problem 2.Motor overload or single-phase preventer 3.All belts got cut *H2 purity may come down
142. H2/ SEAL OIL PANEL LOCAL SUPPLY FAILURE Supply is from TGMCC-C. Check for the reason and eliminate it. 143. STAND BY FANS IN Thyrister cooling fans effectiveness is monitored through flow switch (independent for each fan). They monitor the airflow and initiates auto changeover through a five seconds timer and initiates an alarm, "standby fans in". To reset this alarm the fans selector switch (SVE) is to be brought the running fans position. The fans can fail in any of the following conditions: 1. Motor overload 2. Flow switch sensed low flow 3. Selected power supply failed 4. Control supply failure 5. Main supply ‘under voltage’ if selected to main.
144. SEAL OIL FEEDBACK PRESSURE LOW (5.5) *DC SOP starts 145. INTERVENTION MINIMUM SEAL OIL DP TURBINE TRIP (DP-0.2) Seal oil DP low alarm appears at 0.45 KSC. Rotate the magnetic filter which in service. If feed pressure is OK and this alarm is coming means DPR malopetaion. malopetaion. With the help of E/M change over the DPR. If DPR changing is not helping crack open the DPR bypass valve.
146. SEAL STEAM PRESSURE LOW 1. Load is less so leak off is less. 2. Seal steam regulator malfunction. 3. Unloading valve inadvertent opening. (Gland steam is to seal against steam leakages to atmosphere and from section to section (HP-IP) Labyrinth type shaft pickings provide a series of throttling that limit steam leakage along the Rotating shaft to a minimum as it is throttled from the HP space to LP space. )
147. GLAND (SEAL) STEAM CONDENSER LEVEL HIGH GSC tube leakage *Vacuum may fall 148. ONE OR MORE IN OPERATIVE STRINGS With reference to voltage current leads in capacitive circuit and lags in an inductive circuit. So (R-C network) Capacitors are placed in parallel to thyristers to avoid abrupt changes in voltage. And Inductor or choke (L-network) is placed in series with the thyriseters to avoid abrupt changes in the filed current .The basic purpose is to protect the thyristers. Search coils are placed above the inductor to monitor the thyrister healthiness by sensing current flow through them.
If no current flows this alarm appears 149. SERVICE AIR PRESSURE LOW (3.5ksc, operating pressure 6 ksc) 1.S.A compressor tripped 2.Heavy leakage in PA airline *APH air motor may not run
150. SOOT BLOWING SYSTEM TROUBLE 1.Motor overload 2.Blower gets struck up, fails to retract 3.MOV not closing #Ask burner floor operator for any problem in soot blower 151. THRUST BEARING WEAR HIGH (axial shift shift high) high) 1.Sudden change in load 2.Abrupt change of steam temperature or condenser vacuum 3.Sudden isolation of HP heaters 4.Sudden closure of force close NRVs 5.Failure of lube oil supply to thrust bearing 6.Pick up of load is too quick 7.Wear out of thrust bearing (causing the axial shift) 8. Formatting salt in turbine (causing the axial shift) 9.Wear out of thrust pad (causing the axial shift) 10.Overloading of turbine 11.Steam flow in reheater is high *1.Seal rubbing 2.Mettalic sound 3.Turbine vibration 4.Squealer rings are provided to give an early warning by sound. 5. Squealer rings come into contact before the wheels /collar come into contact #1.Load must be reduced 2.Steam temperature / vacuum must be improved 3.Damaged thrust bearing/ thrust pad have to be replaced
152. TURBINE EMERGENCY TRIP OPERATED/ HYDRAULIC /OVER SPEED 1. Over speed of the turbine will cause the emergency governor to strike the trip finger, which w hich allows The trip piston to travel to its dump position, closing off the trip oil supply from the vacuum trip and Dumping pressure from the various relay cylinders 2. Manual operation of the master trip handle located on the turbine front standard strikes the trip. 153. TG MOTOR STOPPED/ TG DISENGAGED
1.Stopped from console 2.Tripped on overload 3.Supply lost 4.Lub oil pressure switch problem/ lube oil low interlock problem #1.If the rotor rotor is hot and TG motor stopped, try to do barring by hand, by pulling the BG lever over The square head of the shaft on the vertical motor at least by 90 deg every 30 minutes. 2.See for the cause and rectify it. *1.Due to top and bottom temperature DT, distortion of rotor (hogging). 2.Inter stage packing clearances may get affected there by reducing the operating efficiency. 154 . UPS UPS INVERTER TROUBLE 1.DC supply voltage low 2.DC supply voltage high 3.AC output voltage low 4.Input DC supply lost 5.Fan failure 6.UPS failure 7.Out of synchronism 8.Static switch fuse blown 9.Alternate source failure 10.Alternate source deviation 11.One inverter is bypassed 12.Inverter operation abnormal *UPS supply interruption/ loss #Bypass the inverter, which has the trouble See that the other inverter is supplying load
155. UPS CHARGER TROUBLE 1.Charger A/B/C/ AC supply failure 2.Charger A/B/C output bus ground 3.Charger A/B/C/ DC volt low 4.Charger A/B/C no voltage *1.UPS inverter supply may be interrupted 2.Interruption will trip the unit 3.Under voltage may cause electric supply failure #Inform C&I The charger alternate source has to be taken over.
156. UAT OIL LEVEL LOW/ BUCHHOLZ
Leakage in a. Drain b. Gasket Hot spot b. Loose bolts c. Internal faults i. Insulation failure c. Short circuit i. Core to winding ii. Phase to phase iii. Core to core
Unload the transformer and change loads to other source. Inform E/M. 157. UT OIL LEVEL LOW/ BUCHHOLZ Leakage in d. Drain e. Gasket Hot spot d. Loose bolts e. Internal faults i. Insulation failure f. Short circuit i. Core to winding ii. Phase to phase iii. Core to core Unload the transformer and change loads to other source. Inform E/M.
158. UT TEMPERATURE HIGH 90 DEG.C 1. Over load 2. Core fault (eddy current)-Only oil temperature goes high and winding temperature does not change. Following causes may cause high temperature problem Mechanical Devices: a. Buchholtz b. Oil temperature high c. Winding Temperate high d. PRD (Pressure Relief Device) e. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure Electrical: a. Over current b. Over voltage c. Over fluxing d. Earth fault i. Phase to phase ii. Phase to body
iii. iv.
Core to core Core to body
159. UAT TEMPERATURE HIGH 100 DEG.C 1. Over load 2. Core fault (eddy current)-Only oil temperature go high and winding temperature does not change. Following causes may cause high temperature problem Mechanical Devices: f. Buchholtz g. Oil temperature high h. Winding Temperate high i. PRD (Pressure Relief Device) j. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure Electrical: e. Over current f. Over voltage g. Over fluxing h. Earth fault i. Phase to phase ii. Phase to body iii. Core to core iv. Core to body 160 . BOTH VAPOUR EXTRACTION FANS NOT RUNNING 1.EPB 2.Supply problem 3.Motor problem a. Motor over load b. Single phase preventer c. Motor got burnt FUNCTIONS 1.Constantly remove air and hydrogen leakage accumulation from oil tank 2.Remove vapors, which may be harmful to the lube system 3.Keep vacuum in the tank around 8cm of WC. 4.Also prevents oil vapors from oozing out through the oil tank cover and depositing 5.Air trapped in the oil may be pressurized at bearing and tend to blow into the windings where it may Damage the windings 6.Governor open and bearings rusting may be caused due to moisture. More over rust is an active Catalyst, which increases the rate of oil oxidation and shorten the useful life of the oil charged charged *Above things will be affected
#1.See that one of the fans is started 2.Steam parameters must be corrected 3.Lub oil temperature and pressure should be verified and maintained
4.Proper flow of oil to the bearings should be ensured 5.The extraction drains must be kept open 6.Differential expansions should be brought within limits 7.Seal steam pressure and temperature should be verified 8.If the trend is increasing side, trip the turbine and kill vacuum One should not wait the speed to come down to 2000 rpm (2/3 speed) for breaking vacuum, To avoid severe duty on last blades of LPT, as in other cases The most important symptom of crack propagation is the typical increase of vibration of Amplitude of one or two mills with a sudden temperature drop. As the crack progressed in a matter Of weeks, the amount of temperature drop required has decreased, and the resulting vibration Amplitude increased Generally such vibration contain substantial vibration components at the second and third Harmonics of running speed, when analyzed through IRD variable frequency filter analyser In such case stop the unit and notify ANSALDO
161.
6.6KV BUS A/ B INCOMING BREAKER TRIP When Unit trips Bus electrical fault a. Earth fault b. Bus Over current c. Station Incomer closed d. UT oil/ winding temperature high
162.
6.6/ 415 SWGR AUTO CHANGE OVER
Bus under Voltage. (80% through under voltage relay) If this continues and NO Voltage is sensed then all motor feeders trip. (To avoid motor over current) *HT/ LT incomer tripped #Look for proper change over and loads on bus remaining live 163. 415 V BMCC/ VDDC TRIP On electrical fault/ Short circuit/ Sustained over load downstream of the incomer breaker then it trips. Observe for survival of the other section.
164.
UNIT#1 TRIPPED
1.When any unit tripped looks for MVAR changes and acts accordingly 2.Also look if PRDS has taken over (come into service) 3.If in UNIT#1, look for 1S1, 1S2, 2S1, 2S2 supply voltages and maintain
165. UT A/B cooler / OLTC trouble. Cooler fan/pump motor Trouble Supply problem
OLTC supply 3 phase 415 V fail Fans supply to Marshal box to tap changer box Oil operated relay PRD (OLTC Chamber) (Note: UT has no PRD) 166. UT A/B fire: Taken from Deluge valve. (Deluge valve supply from marshalling box. Mulsifire: a. PB b. Lever c. Bulb sensing 6.6 KV bus A/B hot changeover out of synchronization. Mismatch between Unit and Station buses a. Frequency b. Voltage c. Phase sequence 168. UAT Buchholtz/ oil level low
167.
Leakage in g. Drain h. Gasket Hot spot f. Loose bolts g. Internal faults i. Insulation failure i. Short circuit i. Core to winding ii. Phase to phase iii. Core to core Unload the transformer and change loads to other source. Inform E/M. 169. UAT temperature high. High-100 ° C Trip-105 ° C 170. ESP Transformer-A/B buchholtz/Oil level low Leakage in j. Drain k. Gasket Hot spot h. Loose bolts i. Internal faults i. Insulation failure l. Short circuit i. Core to winding ii. Phase to phase iii. Core to core Unload the transformer and change loads to other source. Inform E/M.
171. ESP Transformer-A Temp High Winding hi-95 ° C trip-105° C Oil Hi-80 ° C Trip-90° C 1. Over load 2. Core fault (eddy current)-Only oil temperature go high and winding temperature does not change. Following causes may cause high temperature problem Mechanical Devices: k. Buchholtz l. Oil temperature high m. Winding Temperate high n. PRD (Pressure Relief Device) o. SPR (Sudden Pressure Relay)- Based on rate of rise of pressure Electrical: i. j. k. l.
Over current Over voltage Over fluxing Earth fault i. Phase to phase ii. Phase to body iii. Core to core iv. Core to body 172. Unit & Station transformers parallel. Station breaker did not trip on closing the Unit breaker. Ensure that only one breaker is in service. 173. Unit DC volt Abnormal High voltage (250V) If high voltage is there relay’s coil may get damaged. Solenoid valves, Indication lamps DC motors may fail Under voltage.(185V) Low voltage cause more current to flow leading to overheating of motor. At thresh hold voltage chattering of relays may take place leading to variation in process parameters. 174. Unit Lighting Transformer Buchholtz/ Oil level low Wdg. Hi-95 trip-105 Oil Hi-80 trip-90 1. Over load 2. Core fault (eddy current)-Only oil temperature go high and winding temperature does not change. Following causes may cause high temperature problem Mechanical Devices: p. Buchholtz q. Oil temperature high r. Winding Temperate high
s. t. Electrical: m. n. o. p.
PRD (Pressure Relief Device) SPR (Sudden Pressure Relay)- Based on rate of rise of pressure
Over current Over voltage Over fluxing Earth fault i. Phase to phase ii. Phase to body iii. Core to core iv. Core to body 175. Unit Bus A/B VT trouble. One of the fuses must have failed.
176. Generator TRIP RELAY operated
OVER VOLTAGE GT DIFFERENTIAL LOW FORWARD POWER POLE SLIPPING STATOR EARTHFAULT GENERATIOR DIFFL. GT PRD GT BUCH HOLTZ GT WINDING TEMP LBB EXCITATION FAULTY-A OVERHEAD LINE DIFFL.
àà
86 G àà
TURBINE TRIP RELAY-A TTR-B MAIN BKR BKR (trip coil#1) MIDDLE BKR (trip coil#2) GEN FIELD BKR UT-A I/C UT-B I/C BUS A auto changeover BUS B auto changeover TO 386G TO 486G MIDDLE BKR LBB TO 286G
177. Turbine bearing Vibration High. When the shaft vibration crosses 125 microns this alarm appears. Possible reasons for high vibration could be 1. Oil film distortion 2. Oil temperature temperature variation <38 ° C or > 42 ° C 3. Less seal steam temperature. 4. High moisture /mechanical impurities in the oil 5. Loose/damaged blades 6. Fouling in side the turbine 7. High eccentricity.
# Try reducing load and observe the trend. Trip the turbine if the vibrations cross 200 microns. During coasting down if the vibrations cross 280 microns vacuum breaker is to be opened. Boiler to be hand tripped and boxed up. When TG comes to rest engage the Turning Gear.
178. Turbine bearing temperature high. TRIP the turbine IF Thrust bearing metal temperature crosses 90 ° C OR Sleeve bearing metal temperature temperature crosses 95 ° C. Vacuum to be killed at <2000 rpm speed or 200 mmHg vacuum. Put the machine on barring gear with an advice from turbine maintanance.
179. TOTAL POWER FAILURE. TOTAL POWER FAILURE I nsure starting of EOP nsure Closing of EMCC Incomer from DG set if DG is Running. nsure running of DC SOP. nsure all CVs, Ivs, ESVs closed. Main, Middle, Field breakers Tripped. nsure APH aux motor running nsure DC lighting
TOTAL 220 V DC FAILURES 1. All breaker indication lamps Go dark. 2. Turbine trips through ETD 3. If GRP supply is available Main, Middle, Field breakers Trip. Else Trip them manually After ensuring all CVs ESVs Closure. 4. Filed breaker is to be opened from local. 5.For 6.6 KV buses ensure stand by DC supply by changing over the switch. 6.Ensure charging of EMCC at the earliest and start TGOP. 7. If 6.6KV buses are OK with standby DC source try normalizing LT buses. 8. Ensure running of AOP.
8. 9. 10. 11. 12. 13. 14. 15.
TOTAL POWER FAILURE II 1. Close all Extraction Block valves. 2. Look for flame if any Shown by scanners 3. Ensure DC scanner fan Running 4. Close CBD, SB valve if open. 5. Close RH, SH attemporation Block valves. 6. Reset all ESP fields manually
TOTAL POWER FAILURE III 1. Close main ejector steam valve and break vacuum below 2000 rpm or 200mmHg vacuum. 2. Close seal steam at Vacuum below 100 mmHg.
TOTAL 220 V DC FAILURES 1. ID, FD, PA fans and MILLs will be in service without any protection. 2. On loss of DC, FD fans Get trip command on loss of ID fan running contact. But they remain in service, as there is no DC supply to the tripping coil. 3. Also On loss of Both ID fans MFT acts but no mill or PA fan trips. All feeders trip. 4. On resumption of DC Through standby source to 6.6KV buses all Mills, PA fans, FD fans trip. 5. ID fans remain in service.
TOTAL 220 V DC FAILURE FAILURE
