COMMONLY FACED O&M PROBLEMS OF THERMAL POWER STATIONS
1.0.
BOILER & AUX (COAL, OIL, GAS FIRED):
1.1.
Operational Problems ( Common )
1.2.
Mech. Systems
1.2.1.
1.2.2.
1.2.3.
1.2.4.
1.2.5.
1.2.6.
1.2.7.
1.2.8.
1.2.9.
1.2.10.
1.2.11.
1.2.12.
1.2.13.
1.2.14.
1.2.15.
1.2.16.
1.3.
Controls & Instrumentation :
1.3.1.
1.3.2.
1.3.3.
1.4.
Pressure Parts, Furnace & Second PASS
Safety valves
Isolating valves ( motorised & manual)
Controlled circulation pumps
Control valves
Soot blowers systems
Superheater & Reheater Spray System
Milling system (Bowl mills & tube mills)
Burner tilting system
Coal piping
Oil/Gas firing system
Rotary Air preheaters
FD,PA and ID Fans
Electrostatic precipitator
Water Chemistry System
HP Bypass system (SULZER MAKE)
FSSS
Secondary Air Damper Control
Aux. PRDS
Electrical System :
1.4.1.
1.4.2.
HT Motors
ESP Controls
1.1.
Common Operational Problems of Boiler & Auxiliaries:
1.1.1.
Frequent trips on flame failure
1.
2.
3.
4.
5.
6.
7.
1.1.2.
Furnace draft fluctuations along with flame scanner flickering:
1.
2.
3.
4.
5.
6.
7.
8.
1.1.3.
Check for proper functioning of draft control on `Auto’
Check for disturbed flame condition
Check for proper functioning of CMC/Fuel master control on Auto
Check for proper functioning of PA header pressure auto control
Check for proper functioning of secondary air flow auto Control
Check for proper functioning of SADC on auto control
Check for furnace trough sealing
Check for any boiler tube leakage
Main Steam/HRH steam temperature low/high:
1.
2.
3.
4.
5.
6.
7.
8.
1.1.4.
Check for proper combustion
Check for correct total air flow
Check for correct coal air ratio
Check for correct wind box to furnace DP
Check for proper functioning of SADC
Check for healthiness of flame scanners
Check for flame failure circuit in FSSS
Check for correct total air flow
Check for correct burner tilt position
Check for correct feed water temperature at Economiser inlet
Check for slagging/scaling (external) on water wall, SH & RH
tubes
Operate wall blowers/LRSB at regular interval as per requirement
Check for inside scaling in water walls & SH/RH tubes
Check for choking of SH/RH attemperator nozzles/passing of
SH/RH spray control valves
Check for any undesired steam outlet due to passing of safety
valves, drain valves, vent valves
High unburnt carbon in flyash/bottom ash:
1.
2.
3.
4.
5.
Check for proper and stable combustion
Check for plugged coal pipes and ensure equal distribution in all
four coal pipes
Check and adjust the fineness of coal
Maintain adequate total air flow (secondary air flow + PA flow)
Maintain proper oxygen in flue gas. Cross check UCB
instruments with local sampling
6.
7.
8.
9.
10.
11.
12.
13.
14.
1.1.5.
Tripping of boiler on RH protections due to closure of HP/LP Bypass
during start ups:
1.
2.
3.
4.
5.
6.
1.1.6.
Maintain stable combustion
Study RH protection logic
Initially keep HP/LP Bypass valves on manual mode. After stable
combustion and sufficient flow only they should be put on Auto
Check for proper functioning of these valves on Manual and Auto’
Check protection closing circuit for any malfunctioning
Maintain correct HP Bypass downstream temperature
Unit load not increasing to rated load :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
1.1.7.
Ensure that burner tilt of all four corners is at same position.
Maintain correct mill outlet temperature.
Tune SADC as per requirement to optimize flame condition
Carryout clean air flow test/hot traverse if required
Check and optimise ball charge (Only for Tube mills)
Check and replace worn out mill liners
Check for proper mill clearances
Maintain proper mill level (Only for Tube mills)
Check classifier/reject chute for bypassing of coal air mixture
Check for correct parameters of main steam/HRH steam i.e.
pressure, temperature, flow
Check for correct quantity of coal
Check for proper combustion/flame condition
Check for correct total air flow/Oxygen and CO in flue gas
Check for calorific value, fixed carbon, ash content, moisture etc.
of coal
Check for correct feed water temperature at economiser inlet
Check for correct fineness of coal
Inspect mill and replace worn out liners and internals
Check for correct mill output and take remedial measures to get
optimum output
Check for any boiler tube leakage
Check for undesired steam outlet due to passing of safety valves,
drain valves, vent valves.
Attend all valve leakages
Check for very dirty furnace due to deposition of slag/scale on
water wall/SH/RH tubes
High stack Emission :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
1.1.8.
Tripping of Unit on high/low drum level :
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.1.9.
Check for functioning of all ESP fields
Check for correct total air flow, Oxygen and CO in flue gas
Check for correct flue gas temperature at ESP
Check for proper rapping frequency
Check for proper current settings
Check for proper gas flow distribution in the pass during shut
down
Check for proper fixing of deflector plates of hoppers during shut
down
Check for eroded guide vanes/splitters during shut down
Check for proper fixing of screen plates during shut down
Check for proper closure of manhole doors, inspection doors etc.
to prevent air ingress
Check for proper functioning of ash handling system
Check for high ash content in coal
Check for sudden opening/leakage of waterwall/economiser tube
Check for tripping of any one of running BFPs
Check for malfunctioning of drum level auto control
Check for closure of any valve in feed water circuit
Check for opening of HP Bypass valve on fast opening mode.
Check for sudden throw off/raising of load
Check for tripping of two/three coal elevations simultaneously
Check for disturbance in combustion
Check for malfunctioning of drum level transmitters
Frequent tube failures :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Avoid sudden stress to boiler tubes
Maintain rate of pressurisation/de-pressurisation as
recommended during hydraulic test of boiler
Maintain rate of rise/drop of temperature as recommended during
start-up/shut down (follow start up curve)
Monitor drum/SH/RH metal temperatures during start up/shut
down
DON’T TAKE MILLS INTO SERVICE UNLESS FLOW IS
ESTABLISHED THROUGH REHEATER
Maintain proper water chemistry regime as per recommendations.
Check for tube thickness for any erosion. In case of erosion,
tubes must be replaced
Check for deposits/scales inside the tubes. If found, contact
BHEL for further analysis and chemical cleaning.
Check for possibility of choking
Check for foreign materials/obstructions in the connected headers
1.1.10.
Boiler drum pressure dropping suddenly :
1.
2.
3.
4.
5.
6.
7.
1.1.11.
High DM Water make up :
1.
2.
3.
4.
5.
6.
1.1.12.
Check for any boiler tube leakage
Check for leakages from glands and bonnets of valves
Check for passing of safety valves
Check for passing of drain valves
Check for passing of vent valves
Check for optimum opening of CBD valves
Boiler water silica level High :
1.
2.
3.
4.
5.
6.
1.1.13.
Check for proper DM water quality
Check for correct chemical regime in boiler drum
Check that CBD valves are operative
Check the CBD lines for any possible choking
Check for any condenser tube leakage
Check for proper opening of CBD valves
Sudden reduction of load :
1.
2.
3.
4.
5.
1.1.14.
Check for interruption of coal to the furnace due to choking in the
burner
Check for tripping of feeder/mill
Check for disturbed combustion inside furnace
Check for any boiler tube leakage
Check for opening of boiler drains, vent, safety valves
Check for choking in mills/drop in air flow through mill
Check for malfunctioning of auto control of CMC/Fuel master
control
Check whether it is momentary due to grid disturbance or due to
malfunctioning of turbine governing system
Check for drum pressure. If the trend is increasing, take
appropriate measures to stabilize drum pressure by
reducing/cutting off fuel input to furnace. If necessary, cut off
mills, one by one.
Check for drum level. See whether auto control is able to
maintain drum level. Otherwise take it on manual control.
Check for furnace draft
Check for secondary air flow, oxygen in flue gas.
Ash build up in bottom ash hopper and water walls :
1.
2.
3.
4.
5.
6.
1.1.15.
Check for proper functioning of bottom ash evacuation system
Check for proper functioning of clinker grinder system
Check for proper functioning of scrapper conveyor wherever
provided
Check for any choking of ash evacuation/disposal pipes
Don’t allow building up of ash level in case of non-functioning of
ash evacuation and associated systems.
In case problem is persisting and ash level has started building,
boiler must be stopped and ash/clinker is to be removed.
High Flue Gas temperature at APH outlet :
1.
Check for excess Air and total Air flow
2.
Check for fineness of coal
3.
Check for fouling of water walls, superheaters, reheaters etc.
4.
Check for proper heat transfer in Air preheaters
5.
Check for dampers position of Air preheaters
6.
Check for Burner tilting system and bring it downwards.
7.
Switch over to lower elevation mills.
8.
Check for proper Air distribution and functioning SADC
9.
Check for leakages through peep holes, manholes, seal water
trough etc.
10.
Check for tube failures.
1.1.16.
Low Boiler efficiency :
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.1.17.
Check for excess air flow
Check for the reasons for high air preheater outlet flue gas
temperature
Check for higher unburnt carbon in bottom ash and fly ash
Check for proper combustion and high `CO’ in flue gas
Check insulation/refractory to arrest heat loss
Check for entry of excess water/moisture alongwith coal. Arrest
where possible.
Check the fineness of coal
Check for proper Air distribution and functioning of SADC.
Check for steam/water leakages and tube failures.
High excess Air flow :
1.
2.
3.
4.
5.
Check the Air flow distribution and functioning of SADC
Check the combustion
Check the fouling of superheater, reheater and HTSH surfaces
Check for air ingress through peep holes, manholes, seal trough
etc.
Check the reliability of air flow and O2 measurements
6.
7.
Check the fineness of coal and functioning of mills.
Set for proper air flow and O2 in Automatic combustion control.
1.2.
Mechanical System :
1.2.1.
Pressure Parts :
1.2.1.1.
Water Wall tube failure :
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.2.1.2.
Superheater/Reheater/Economiser/Tube failure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
1.2.1.3.
Check for deposits inside the tube. Analyse the deposits.
Check for indications for overheating of the failed tube and the
nearby tubes.
Check the tube thickness of the failed tube and also nearby tubes.
Check the healthiness of nearby wall blowers for steam passing
Check for possibility of choking/loss of adequate flow through the
tube
In case of scales/chemicals deposits/Rust contact BHEL for
further analysis and chemical cleaning
Check for foreign materials/obstructions in water wall ring headers
Check for possibility of failure of weld joint
Check the orifices of the tubes in the ring header in case of
controlled circulation boilers.
Check for indications for overheating of the failed tubes and the
nearby tubes
Check for failure of weld joint
Check the tube thickness of the failed tube and the nearby tubes
Check the healthiness of nearby long retractable soot blower for
steam passing
Check for possibility of choking/loss of adequate flow through the
tubes
Check for foreign materials/obstructions in the connected
headers
Check the tube material for usage of proper grade material
In case of scales/chemicals deposits/rust contact BHEL for further
analysis and remedial measures
Check the spacing and alignment of coils around the failed tube
Check the availability/healthiness of tube shields/cassette baffles
Unloading/overloading of hangers :
1.
2.
3.
Verify the correctness of the hanger as per hanger schedule
Reset all the hangers of the connected header, pipe, pressure
part to the cold set values.
Measure the hot value of the hanger and report to Engineering for
analysis.
1.2.1.4.
Fast erosion of water walls, superheaters, Reheaters & Economisers
tubes:
1.
2.
3.
4.
5.
1.2.1.5.
Distortion/dislocation of Buck stay structures:
1.
2.
3.
1.2.1.6.
Check for possibility of local explosions and take preventive
measures for recurrence.
Check for expansion obstructions
Contact BHEL for review of design
Erosion of headers in Flue Gas path :
1.
2.
1.2.1.7.
Check the operation of wall blowers/LRSBS w.r.t. possibility of
steam erosion
Provide additional tube shields/baffles for the tubes where there is
faster erosion.
Check the healthiness of existing tube shields/baffles
Use erosion prevention methods around burner blocks, wall
blowers etc.
Contact BHEL for flow model studies
Check for any longstanding steam/water leakages from Hand
holes etc.
Apply additional refractory for the affected position after
consulting BHEL.
Ash Deposits over water walls/superheaters/reheaters/economisers:
1.
2.
3.
4.
Check the operation of wall blowers and LRSBS. Reset the
schedule to prevent excessive deposits
Check the combustion parameters
Check the fineness of coal.
Check the healthiness of secondary Air damper system
1.2.2.
Safety Valves (Spring Loaded and Electromatic):
1.2.2.1.
Set pressure/blow down got disturbed:
1.
2.
3.
4.
1.2.2.2.
Missing of Blowdown rings lock pins:
1.
2.
1.2.2.3.
Check the lower ring setting and also upper ring
Check for erosion of seat/disc during shut down
Check the position of lift collar and its locking
Check overlap collar/orifice healthiness during shut down
Safety valve did not, reset after floating
1.
2.
3.
4.
5.
1.2.2.5.
Check for looseness of lock pins of all safety valves which can
lead to falling of lock pins
Replace the lockpins after proper setting of upper and lower rings.
Valves passing/valves simmering:
1.
2.
3.
4.
1.2.2.4.
Check for loosening of lock nut of pressure adjusting nut
Check for lower and upper lock pins looseness/non-availability /
breakage
Check for disturbance of overlap collar setting
Reset the set pressure/blowdowns.
Check for disturbed lift collar position. Check for missing lock pin
of lift collar
Check for loose locknut of pressure adjusting nut
Reduce the pressure till the safety valve resets
Correct the lift collar, pressure adjusting nut positions
Refloat the safety valve
Blowdown adjustment could not be done with upper ring :
1.
2.
3.
Check for seat/disc erosion during shut down
Check overlap collar and its orifice
Adjust overlap collar position one notch at a time and reset
blowdown.
1.2.4.
Controlled Circulation Pumps (600 MW) Boilers :
1.2.4.1.
CC Pump differential pressure low :
1.
2.
3.
4.
1.2.4.2.
Sudden rise in cavity temperature :
1)
2)
3)
4)
5)
6)
1.2.4.3.
3)
4)
5)
6)
Arrest the leakages at the earliest, if possible
Open the purge water to motor to make up the loss and prevent
boiler water entry into motor
Ensure the availability of cooling water to coolers
If the leakage is from weld/flange joint and can not attended by
normal means, on line sealing methods can be resorted to.
If needed isolate the pump or stop the Boiler and attend to the
leakages
Ensure that cavity temperature is maintained below 60 Deg.c. to
prevent damage to the motor
High differential temperature across the pump (with pump not in
operation) :
1.
2.
1.2.4.5.
Check for leakages/back charging from the cavity of motor
towards purge water line
Check for leakages in the impulse piping of cavity water pressure
Check for external leakages/tube leakages of the motor coolers
Check for accidental opening/passing of drain valve of purge line
before motor
Check for failure of cooling water to motor coolers
Check for leakages from the bushings
Water leakages from the motor/motor cooler
1)
2)
1.2.4.4.
Check whether Direction of rotation is proper
Check for healthiness of the DP Transmitters and the connected
control system
Check for choking/leakages in DP transmitter impulse lines
Ensure discharge valve is open
Open the warm line and wait for reduction in differential
temperature
Check for plugging of warm up line
Leakage from cooler (High pressure side) circuit:
1.
Start the purging immediately
2.
3.
4.
5.
Stop the motor
If leakage can not be arrested, isolate the pump/stop the boiler
Try for `ON LINE SEALING’ methods to arrest the leakage or
attend OFF line.
Prevent rise of cavity temperature beyond 60 Deg.C. to protect
motor.
1
1.2.6
Soot Blower System
1.2.6.1
Wall Blowers
1.2.6.1.1.
Soot blower valve head does not open
1.
2.
3.
4.
5.
6.
1.2.6.1.2.
Blower Pressure/Flow is flow/high :
1.
2.
3.
1.2.6.1.3.
Inspect the stem for any pitting/bending/damages
Inspect the valve body for any dirt & clean.
Inspect the valve seat for any dent/scratch. Lap the seat with disc.
Check whether the spring is struck up or lost its strength.
Blower is jammed/not operating :
1.
2.
3.
4.
5.
6.
7.
1.2.6.1.5.
Check the pressure setting bolt
Check the operation of pressure control valve at soot blower
station
Maintain recommended pressure
Soot blower valve head does not close after blowing:
1.
2.
3.
4.
1.2.6.1.4.
Check & set the pressure setting bolt.
Check the gland tightness.
Check whether valve stem is jammed/bent.
Check the valve seat for any damages.
Check the limit switches.
For further service , contact maint. Engg.
Check the swivel tube fouling with shroud tube.
Check the swivel tube /guide rods for cleanliness.
Check that gland packing is not too tight .
Check the swivel tube against any pitting .
Check the limit switch setting.
Check oil level in gear box
For further service ,contact
Motor becomes overloaded :
1.
2.
3.
4.
Check the tightness of gland packing
Check the cleanliness of swivel tube,guide rods , rack & pinion.
Check oil level in gear box
Check healthiness of motor/cable/MCC
1.2.6.2.
Long Retractable Soot Blowers
1.2.6.2.1.
Soot blower jamming :
1.
.
1.2.6.2.2.
2.
3.
4.
5.
6.
Motor Overload :
1.
2.
3.
4.
5.
6.
1.2.6.2.3.
Check the oil level & oil quality
Vibration while operating :
1.
2.
1.2.6.2.7.
Check & tighten the chain properly
Grinding sound in Gearbox :
1.
1.2.6.2.6.
Check for any weak links.
Check whether circlips in chain links are properly available.
Check that chain is not too tight
Chain is coming out of housing :
1.
1.2.6.2.5.
Check whethert lance tube is fouling with boiler tube or wall
sleeve.
Check the tightness of gland bush /gland packing.
Check the setting of overload relay/MCC.
Check the accumulation of dirt over the rails.
Check the motor for insulation & winding .
Check the cables for any damage.
Failure of Traverse Chain :
1.
2.
1.
1.2.6.2.4.
Check for any physical obstruction of travelling carriage with
housing .
Check for limit switch failure
Check the gland tightness.
Check for lance tube fouling with boiler tube or wall sleeve.
Check whether scrapper plate bolt is broken .
Check oil level in gear box
Check for any obstruction of travel carriage in housing
Check for proper chain tension
Sootblower overrun :
1.
2.
Check for traverse chain failure.
Check the limitswitches ,timer setting.
3.
4.
1.2.6.2.8.
Overheating of Lance Tube :
1.
2.
3.
4.
1.2.6.2.9.
2.
Check the quality of packing ,tightness ,wear of packing etc.,
Check stem for any scratches, dents etc.
For further service , contact
Valve seat leakage :
1.
2.
3.
1.2.6.2.12.
Check the quality of packing, tightness ,wear & tear of glands
etc.,
Check the feed pipe for any surface defects such as scratches
,dents etc.,
Steam leakage through valve stem :
1.
2.
3.
1.2.6.2.11.
Check the blowing pressure & verify whether valve opening bolt is
available.
Check the operation of valve stem .
Check the flue gas temperature for any increase.
Check whether flow protection is in service
Steam leakage through travelling carriage :
1.
1.2.6.2.10.
Check for any failure of contactor & contactor reverse coils.
Check whether thermal overload relay for traverse motor has
operated/fuses are blown and find out the causes.
Check the gland packing for proper tightness
Disassemble and inspect the valve disc and valve seat for any
damage /corrosion.
Check whether valve opening bolt is pressing while the travelling
carriage is in home position .
Limit switch failure :
1.
2.
3.
4.
Check the limit switch contacts for quality
Check the failure of internal parts such as springs ,locking
notches etc.,
Check the assembly /direction for correctness .
Check for any accumulation of foreign material /dirt in limit switch.
1.2.7. Excessive superheater/ Reheater spray:
2.
3.
Check the healthiness and position of burner tilting system. Bring
the tilts down
Check fineness and proximate analysis of coal
4.
5.
6.
7.
8.
9.
Check the proper functioning of spray flow meter
Increase wall blowers operation frequency
Reduce excess Air to the rated value
Check windbox/primary air pressure
Operate lower elevation mills
Tune Automatic Superheater/Reheater temperature control
1.2.8.2.
Bowl Mills :
1.2.8.2.1.
Abnormal Noise/vibration in Separator Body.
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.2.8.2.2.
Abnormal Noise in Mill side :
1.
2.
3.
4.
5.
1.2.8.2.3.
3.
4.
5.
6.
7.
Check for worm shaft bearing failure
Check for improper surface contact of some teeth of worm wheel
and worm shaft
Interference of pump hub with bushing
Check for worn out/dry coupling
Check for failure of vertical shaft bearings
Check for temperature rise of any bearing
Check for lubrication of upper vertical shaft bearing
Overflow of oil from Mill Base/pressurisation of Mill base.
1.
2.
3.
4.
5.
1.2.8.2.5.
Check for touching of scrapper with stationary parts
Check for skirt assembly touching the mill bottom
Check for breakage of scrapper assembly
Check for presence of foreign material under scrapper
Check for accumulation of coal in pyrite hopper and mill side
Abnormal Noise in Mill Base :
1.
2.
1.2.8.2.4.
Check for ingress of foreign material in the Mill
Check for roller touching the bowl.
Check for Bowl assembly touching the stationary parts.
Check for proper compression of springs
Check for Journal spring assembly bearing failure
Check for increase of feeder speed to increase the coal flow to
the Mill
Check for loosening of separator body bolts
Check the correctness of bull ring segments
Check the bull-ring segments for excessive wear
Check for Air leakage through Dust guard/Mechanical face seal
into gear box
Check for damages of mechanical face seal/Dust Guard Seal
Check for opening of upper bearing cover
Check for oil cooler tube puncture
Check for excess oil level in mill base
Hot Air dust leakage from cored holes of mill base :
1.
1.2.8.2.6.
No return oil from vertical shaft upper radial bearing (Internal Lubrication
Mill)
1.
2.
3.
4.
1.2.8.2.7.
Check for damage of gasket or use of improper gasket
Check for loose/missing bolts
Use of proper sealing after proper cleaning of the making
surfaces
Mill Base Oil Temp High :
1.
2.
3.
4.
5.
6.
1.2.8.2.11.
Check for puncture of oil cooler tubes.
Check for breakage/leakage of return oil line
Check for vertical shaft oil seal in upper bearing housing
Oil leakage from flanges :
1.
2.
3.
1.2.8.2.10.
Check for improper/damaged gland packing
Air vent pipe of Mill base closed/plugged
Oil leakage from cored holes of Mill base :
1.
2.
3.
1.2.8.2.9.
Check for plugging of vertical shaft hole
Check for plugging/breakage of return oil line
Check the clearance between the pump and the hub
Check for plugging of holes in the lower bearing housing
Oil leakage from worm shaft packing gland
1.
2.
1.2.8.2.8.
Check mechanical face seal/dust guard seal
Check for choking of oil cooler pipes
Check whether cooling water is charged with adequate pressure
Check for proper oil level
Check the quality of the oil. Check mechanical impurities and
moisture in oil
Check the matching of worm and worm gear
Check for worn out damaged bearings
Mill Coal Spillage high :
1.
2.
3.
Check for healthiness of rolls and then clearance with respect to
Bowl
Check the wear out of Bull Ring segment, Bull Ring segment,
worm wheel, Bowl extension ring etc.
Check for the Jammed rolls
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
1.2.8.2.12.
Non uniform spring deflection :
1.
2.
3.
1.2.8.2.13.
Check setting of classifier
Check alignment of classifier vane
Check for puncture/plugging of classifier cone
Check for wear out of Roller and Bull Ring segments etc.
Check Ring Roll clearance
Maintain proper air flow and mill outlet temperature
Check for air bypassing of separator body liner
Check for journal spring compression
High Pulveriser Fuel Fineness
1.
2.
3.
1.2.8.2.16.
Check Dust Guard and Mechanical Face seal
Check the oil seal of upper bearing housing
Low pulveriser Fuel Fineness :
1.
2.
3.
4.
5.
6.
7.
8.
1.2.8.2.15.
Check unequal spring compression
Check for unequal roll wear
Check for improper ring-roll clearance
Mill base oil contamination:
1.
2.
1.2.8.2.14.
Maintain proper air flow
Check for water ingress along with coal
Check for pyrites along with coal
Check for damaged vane wheel assembly
Check the clearances between vane wheel w.r.t. separator body
Avoid over-loading of Mill
Maintain proper Mill outlet temperature
Reset Ring roll clearance, Journal head and Pr Spring seat
clearance
Check Journal spring compression
Check the setting of the classifier
Check for journal spring compression
Check setting of classifier
Recheck sampling technique
Mill Fires :
1.
2.
3.
Choking of Mill with coal
Filling of pyrite hopper and mill bottom with coal
Spill over of coal to mill inlet air duct
4.
5.
6.
7.
8.
9.
10.
1.2.8.2.17.
Vertical shaft failure :
1.
2.
3.
4.
5.
6.
7.
8.
1.2.8.2.18.
Check for low quality of coal
Check for high moisture in coal
Check and set classifier setting
Check spring compression
Maintain proper air flow and mill outlet temperature
Check ring roll clearances
Check for worn out parts
Check plugging of coal pipe and closure of one or more mill
discharge valves.
Mill Discharge valve not operating :
1.
2.
3.
4.
5.
1.2.8.2.20.
Check for the equal spring compression
Do not use roller with unequal wears
Check for breakage of one of the spring
Check for entry of heavy foreign material in the mill
Check for improper locking of spring assembly
Check for improper ring roll clearance
Check for jamming of rolls
Check for jamming of Trunion Bushing
Low Mill output :
1.
2.
3.
4.
5.
6.
7.
8.
1.2.8.2.19.
Maintain proper air flow
Check for improper classifier settings
Check for excessive ingress of water along with coal leading to
improper grinding
Check for wear-out of parts.
Check for closure of MDV and plugging of coal piping
Check for quality (high volatile matter) of coal
Maintain proper mill outlet temperature
Check the clearance between top and the body
Check the seals of the power cylinder
Check for proper compressed air pressure
Arrest leakages in compressed air tubing
Check the operation of solenoid valve and the control system
Classifier vane not operating
1.
2.
3.
4.
Check the clearances between classifier vanes and separator
Check the classifier vane shaft straightness
Check uniformity in the length of the link lever
Check for damage to bearings and oil seals
1.2.8.2.21.
Oil leakage from journal assembly
1.
2.
3.
1.2.8.2.22.
Journal Oil Contamination :
1.
2.
3.
4.
5.
1.2.8.2.23.
Check for improper surface contact between bull ring and bowl
Check for heavy foreign material ingress in mill
Check for excessive wear of bull ring
Check for any mill fires
Check for material quality
Worm shaft bearing failure :
1.
2.
3.
4.
5.
6.
7.
1.2.8.2.27.
Check for inadequate clearance between skirt and mill bottom
Check for warpage of skirt causing rubbing
Check for Mill fires and inadequate insulation
Bull Ring segment Crack :
1.
2.
3.
4.
5.
1.2.8.2.26.
Check for entry of heavy foreign material in Mill
Check spring compression
Check ball bearing failure
Mill bottom cracking :
1.
2.
3.
1.2.8.2.25.
Check for quality of oil
Check for damaged seals
Check for damage of bearings
Check oil level
Check for oil filling cap missing/loosening
Spring Adjusting Stud failure
1.
2.
3.
1.2.8.2.24.
Check for damage of oil seal (O ring)
Check for damage for upper journal assembly lip seal
Check for damaged journal shaft (seating area of oil seal)
Check the quality of oil and replace the oil id needed
Check the quality of the bearings
Check the bearing housing damage
Check for improper installation methods
Check for excessive backlash in worm gear
Check for improper matching of worm and worm gears
Check for damage of thrust bearing spring
Vertical Shaft Gear Lub lock nut failure
1.
2.
3.
1.2.8.2.28.
Insulation cover plate warpage :
1.
2.
3.
1.2.8.2.29.
Check for damage to cover plate due to fire
Check for improper expansion clearances between segments of
cover plate
Check the quality of the cover plate material
Roller Assembly Slipping into Mill :
1.
2.
3.
1.2.8.2.30
Check for failed worm shaft bearings
Check for proper matching of worm shaft and worm gear
Check for damaged bearings
Check for keeper plate screw failure
Check for journal shaft Pin/Lock nut failure
Check for improper lubrication
Frequent Oil Filter choking :
1.
2.
3.
Check mechanical face seal
Check that proper filter is used
Check the quality of the oil (mechanical impurities)
1.2.9.
Burner tilting system :
1.2.9.1.
Burner tilts fail to operate
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
1.2.9.2.
Breaking of shear pins of one or more sections :
1.
2.
3.
4.
5.
6.
7.
8.
1.2.9.3.
Check for adequate compressed air pressure and also clean air
filter.
Check that compressed air is free of moisture & mechanical
impurities
Arrest leaks in compressed air tubing and also signal air tubing
Check for synchronised installation of the sections of each corner
burner tilting mechanism
Check for failed shear pins
Check for distorted coal and air buckets (tips) in shut down
Check for fouling of coal, air nozzles in shut down
Check for damaged oil gun/flame scanner assemblies in shut
down
Check for centering and proper clearances of coal nozzles and
buckets in shut down
Check for damages of linkage mechanism during shut down
Check for proper alignment of power cylinder with burner tilting
mechanism
Do not exceed design firing rate per elevation
Lubricate in pins of linkages and coal/air buckets during overhaul
Check the connected control system
Check for jamming/distortion of linkage mechanism
Check for fouling of buckets with each other and also with
stationary parts.
Check for fouling of coal buckets (tips) with nozzles
Check for centering of coal nozzles w.r.t. coal buckets.
Check for distortion/overheating of coal buckets/nozzles
Check for erosion of coal nozzles/buckets
Check for free movement of coal/air buckets
Check for proper clearances of linkages, coal/air buckets (tips)
Erosion of coal nozzles/buckets/burner panels
1.
2.
3.
Check for proper velocities of coal/air mixture. Carryout clean air
flow test/hot traverse
Check the erosion properties of coal
Carry out hard facing of coal nozzles/buckets/burner panels etc.
in consultation with BHEL
1.2.10.
Coal Piping :
1.2.10.1.
Unequal flow through four pipes of any elevations :
1.
2.
3.
4.
5.
6.
7.
1.2.10.2.
Check for full opening of mill outlet gates
Check for full opening of isolating gates at burner inlet
Check for coal deposits in coal pipes
Ensure purging of all four pipes during every start up and shut
down of mills
Check for proper closing of purge air dampers (for tube mills)
during mill operation
Check for erosion of orifices in coal pipes. Replace them
Carry out clean air flow test and ensure that variation in flow
through four coal pipes is within limits
Explosions in coal pipes (for tube mills) :
1.
2.
3.
Ensure proper PA flow through coal pipes to avoid setting of coal
dust in coal pipes
Ensure purging of all four pipes with adequate PA flow during
every start up and shut down of mills
Maintain adequate mill outlet temperature
1.2.11.
Oil Firing system :
1.2.11.1.
Oil firing system :
1.2.11.1.1.
LDO/HFO pump is not developing adequate pressure :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
1.2.11.1.2.
HFO circulation from FOPH to boiler and back not getting established:
1.
2.
3.
4.
5.
6.
7.
1.2.11.1.3.
Check for proper line up of the system i.e. the required valves are
open.
Check whether strainers are clean
Check for adequate level in LDO/HFO tank
Check for proper setting of pumps relief valve
Check for optimum opening of pressure control valve and proper
functioning on auto
Check for proper functioning of team tracing / electrical heat
tracing for HFO system
Check for adequate temperature for HFO system
Check for any air pockets in the system. Vent out air from filter
vents
Check for DP across filter
Check for water contamination in HFO system
Check for mechanical impurities in HFO system
Check for solidification/choking of oil in the lines
Check for correct line up of the system through short/long
recirculation
Check for correct pump discharge pressure (refer 1.2.11.1.1.)
Check for proper functioning of steam tracing/electrical heat
tracing along with the lines
Check for DP across all filters in the circuit. Clean filters if
required
Check for air locking in system. Vent out entrapped air
Check for correct temperature of oil at pump suction and heaters
outlet
Check for any solidification in the lines (for LSHS).
Oil gun not proving:
1.
2.
3.
4.
5.
6.
Check for gun choking
Check for HEA ignitor spark
Check for correct position of HEA spark
Check for healthiness of flame scanners
Check for correct pressure of atomizing medium
Check for correct pressure of LDO/HFO
7.
8.
9.
10.
11.
12.
Check for correct temperature of HFO
Check for correct secondary air flow
Check Wind box pressure and furnace draft
Check for proper line up for oil guns w.r.t. manual isolating valves
and local gun maintenance switch
Check the permissives for oil gun are available.
Check for proper functioning of FSSS system
1.2.12.
ROTARY AIR PREHEATERS :
1.2.12.1.
Excessive Air leakage from Air side (Primary/Secondary) to Flue Gas
side
1.
2.
3.
4.
1.2.12.2.
Excessive Noise/Vibrations from Air Preheater
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.2.12.3.
Check seal gaps which may be too less
Check whether secondary/primary Air side dampers are open
Check whether Air preheater is in bottled up condition
Check for foreign objects over rotor
Check for bad bearings
Check whether there is water/Mechanical Impurities in lub oil of
bearings.
Check for any loosening of seals
Check the main drive and the pin rack alignment.
Check for low lub oil level in bearings
Rotor does not turn :
1.
2.
3.
4.
5.
6.
7.
1.2.12.4.
Inspect all seals (Radial/leaf/Axial/static)
Adjust the seal gaps as specified
Replace the damaged/distorted seals
Check O2 % in Fluegas at Air preheater outlet
Check the Drive unit
Check the oil level in Hydraulic coupling. Also check for blown
fuse of hydraulic coupling.
Check for foreign objects on rotor
Check for bearing damages
Check whether the drive pinion fell down from its position
Check Electrical system/Air motor problems
Check for excessive ash accumulation over the rotor
Drive Unit overheats :
1.
2.
3.
4.
5.
6.
7.
Check lubrication in drive unit
Check for bad seals/rubbing seals
Check for drive pinion/pin rack rubbing
Check for foreign objects/Ash accumulation over rotor
Check the condition of bearings
Check for expansion problems
Check for low lub oil level in bearings
1.2.12.5.
Support bearings/Guide bearing lub oil temperature too high :
1.
2.
3.
4.
5.
1.2.12.6.
Lub oil Foamy :
1.
2.
1.2.12.7.
2.
3.
4.
5.
6.
Excessive Ash accumulation (which is normally wet) over the
heating elements.
Oil/Ash deposits in heating elements, particularly cold end/middle
basket.
Operate the soot blower (if necessary continuously)
Water wash OFF line, if soot blower is not effective
If water washing is not effective, take out the heating elements
and clean them
Check for damaged/eroded heating elements
Fluctuations in Main drive Ammeter current :
1.
2.
3.
4.
1.2.12.9.
Check for Air entry into lub oil system on the suction side of the
pumps
Check for the quality of oil. Replace lub oil if necessary
Excessive pressure drop across Air Preheater
1.
1.2.12.8.
Check the quality of lub oil. Check for water/mechanical
impurities in lub oil.
Ensure cooling water availability to lub oil coolers
Check whether lub oil pumps not operating/pumps not developing
pressure leading to no lub oil circulation
Check for excess hot air leakage around the bearings. Arrest the
hot air leakage
Check for damaged bearings
Check & adjust seal gaps
Replace damaged/distorted seals
Check the bearings for damages
Check whether there is water mechanical impurities in lub oil
Abnormal increase in Air/Flue gas temperatures or in temperatures
detected by Fire Sensing Scanners
1.
2.
3.
Check for possibility of fires inside the air preheater
In case of fire, stop the boiler and isolate the air preheater. Stop
all fans.
Quench the fire using large quantities of water. Do not use CO2
Foam/steam.
4.
1.2.12.10.
Increase in gas outlet temperature and steady fall in Air preheater outlet
temperature.
1.
2.
3.
1.2.12.11.
2.
Check for lub oil level/quality of lub oil
Dismantle and service the air motor
Replace the damaged components
Ensure the working of the lubricator/filter in the compressed air
line
Melting of thermal plug and draining of oil from Fluid coupling :
1.
2.
1.2.12.16.
Check Air leaks/flue gas leaks over the pin rack. Arrest the
leakages
Replace the damaged pin rack
Jamming of Air Motor :
1.
2.
3.
4.
1.2.12.15.
Check for filter choking. Clean/replace the filter
Check for closed valves. Line up the system properly
Check for damaged lub oil pump
Check for availability of lub oil in the bearing
Check for quality of lub oil
Erosion of PIN RACK :
1.
1.2.12.14.
Check for dampers position. One or more dampers might have
closed.
Check for rotor rotation. Check for rotor stoppage alarms.
Isolate the Air preheater in case rotation stopped
Excessive pressure build up/No pressure build up of lub oil pumps:
1.
2.
3.
4.
5.
1.2.12.12.
Refer `Air preheaters fires’ Section of O&M manual
Check for free rotation of Main drive and the rotor.
Replace the thermal plug and maintain proper oil level.
Heavy ash accumulation over rotor, on flue gas side
1.
2.
3.
Check for tube leakages in second pass, which leads to wetting/
accumulation of ash
Check for plugging of hopper below economiser
Check for fouled air preheater elements
1.2.12.17.
Oil deposits in heating elements, especially in cold end baskets :
1.
2.
3.
4.
1.2.12.18.
Check the combustion of oil guns
Check the operation of soot blower
Check the water washing system and its nozzles. Water wash
the elements when flue gs temperature is below 100 Deg.C. after
stopping the boiler.
In case of heavy choking, take out the elements and clean
Soot blower not functioning :
1.
2.
3.
4.
5.
Check and trouble shoot electrical/mechanical problems
Check whether swivel tube got free from the gear box
Check the alignment of swivel tube
Replace the damages parts
Operate the soot blower atleast once in eight hours
1.2.13.
FD, PA & ID Fans :
1.2.13.1.
FD Fan (Axial Reaction Type with Blade Pitch Control) :
1.2.13.1.1.
High Vibrations :
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
1.2.13.1.2.
Unquite running :
1.
2.
3.
4.
1.2.13.1.3.
Check for any deposits on impeller, rotor etc.
Check bearing clearances/bearings healthiness
Check for touching rotating parts with the stationary parts. Check
the clearances.
Check the impeller clearances w.r.t. casing and correct
High bearing temperatures of bearings of Fan/Motor :
1.
2.
3.
4.
5.
1.2.13.1.4.
Check the looseness of bearing pedestal bolts, impeller hub bolts,
blades fixing bolts, coupling bolts etc.
Check proper seating of lub on shaft flange
Check whether any balance weights of the blades fell down
Check whether the blades are installed serially as per the punch
marks and of the same series.
Check whether there are deposits over the impeller, over the
blades, etc.
Check the alignement with motor
Check for any abnormal sound from the bearings of Fan and
Motor
Check for any temperature rise of the bearings.
Carryout vibration analysis to pinpoint possible reason.
In case it is unbalance, carry out balancing to correct the
vibrations
Check that lubrication is proper. Check oil level, flow, pressure
etc.
Check the functioning of lub oil system and cooler.
Check the quality of oil and impurities in oil (Moisture/mechanical
impurities)
Check for bearing damages
Check alingment
Fan attains fall-load immediately after starting/no control on Fan output:
1.
2.
Check whether impeller blades are in full open position
Check whether servomotor got free from the actuator. If so,
reconnect and set the operation of blades with the actuator.
3.
1.2.13.1.5.
Blade pitch control inoperative :
1.
2.
3.
4.
1.2.13.1.6.
Check the setting of servomotors of the fans and correct
Check the control systems and ensure the blade pitch controls
operation is in Unison
Large pressure fluctuations in control oil pressure :
1.
2.
3.
4.
5.
1.2.13.1.9.
Check the servomotor and replace the damaged seals
Two Fans operating in parallel do not absorb same power :
1.
2.
1.2.13.1.8.
Check the actuator and the connected control system
Check whether control oil pressure is adequate
Check whether servomotor is operative
Check whether blades are jammed
Control Oil leakage from Servomotor :
1.
1.2.13.1.7.
Check the setting of servomotor w.r.t. actuator. If found
disturbed, reset it.
Check that the speed of the actuator is matching with that of
servomotor
Check the position of manual recirculation valve
Check the setting of pressure relief valve
Check for leakages in the servomotor and control oil system
Check the N2 pressure in accumulator
Frequent drop in oil level in the tank :
1.
2.
3.
4.
5.
Check the leaks in lub oil system
Check the leakages in control oil system
Check for damaged seals of bearing housing
Check the damage of seals of servomotor
Check the cooler for any leakages
1.2.13.1.10. Water Contamination in lub oil :
1.
Check the cooler for any lube leakages, by HT Rectify the leaking
tubes
1.2.13.1.11. Drop in oil pressure :
1.
2.
Check the filter elements
Check for leakages in lub oil/control oil system
3.
4.
5.
Check the operation/setting of recirculation valve/pressure relief
valves
Check the lub oil pressure control valve
For further service/advice contact………
1.2.13.2.
PA Fans :
1.2.13.2.1.
PA Fans (Axial Reaction Type with Blade Pitch Control)
1.2.13.2.1.
High Vibrations :
1.
11.
12.
13.
14.
15.
16.
17.
18.
19.
1.2.13.2.2.
Unquiet running :
1.
2.
3.
4.
5.
1.2.13.2.3.
Check for any deposits on impeller, rotor etc.
Check bearing clearances/bearings healthiness
Check for touching rotating parts with the stationary parts.
Check the clearances.
Check the impeller clearances w.r.t. casing and correct
High bearing temperatures of bearings of Fan/Motor :
1.
2.
3.
4.
5.
1.2.13.2.4.
Check the looseness of bearing pedestal bolts, impeller hub bolts,
blades fixing bolts, coupling bolts etc.
Check proper seating of hub on shaft flange
Check whether any balance weights of the blades fell down
Check whether the blades are installed serially as per the punch
marks and of the same series.
Check whether there are deposits over the impeller, over the
blades, etc.
Check the alignement with motor
Check for any abnormal sound from the bearings of Fan and
Motor
Check for any temperature rise of the bearings.
Carryout vibration analysis to pinpoint possible reason.
In case it is unbalance, carry out balancing to correct the
vibrations
Check that lubrication is proper. Check oil level, flow, pressure
etc.
Check the functioning of lub oil system and cooler.
Check the quality of oil and impurities in oil (Moisture/mechanical
impurities)
Check for bearing damages
Check alignment
Fan attains fall-load immediately after starting/no control on Fan output:
1.
2.
3.
1.2.13.2.5.
Blade pitch control inoperative :
1.
2.
3.
4.
1.2.13.2.6.
Check the setting of servomotors of the fans and correct
Check the control systems and ensure the blade pitch controls
operation is in Unison
Large pressure fluctuations in control oil pressure :
1.
2.
3.
4.
5.
1.2.13.2.9.
Check the servomotor and replace the damaged seals
Two Fans operating in parallel do not absorb same power :
1.
2.
1.2.13.2.8.
Check the actuator and the connected control system
Check whether control oil pressure is adequate
Check whether servomotor is operative
Check whether blades are jammed
Control Oil leakage from Servomotor :
1.
1.2.13.2.7.
Check whether impeller blades are in full open position
Check whether servomotor got free from the actuator. If so,
reconnect and set the operation of blades with the actuator.
Check the setting of servomotor w.r.t. actuator. If found disturbed
reset it.
Check that the speed of the actuator is matching with that of
servomotor
Check the position of manual recirculation valve
Check the setting of Relief valve
Check for leakages in the servomotor and control oil system
Check the N2 pressure in accumulator
Frequent drop in oil level in the tank :
1.
2.
3.
4.
5.
Check the leaks in lub oil system
Check the leakages in control oil system
Check for damaged seals of bearing housing
Check the damage of seals of servomotor
Check the cooler for any leakages
1.2.13.2.10. Water Contamination in lub oil :
1.
Check the cooler for any lube leakages, by HT Rectify the leaking
tubes
1.2.13.2.11. Drop in oil pressure :
1.
2.
3.
4.
Check the filter elements
Check for leakages in lub oil/control oil system
Check the operation/setting of recirculation valve/pressure relief
valves
Check the lub oil pressure control valve
1.2.13.3.
ID Fans :
1.2.13.3.1.
High Vibrations :
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.2.13.3.2.
High bearings temperatures of the bearings of Fan & Motor :
1.
2.
3.
4.
5.
6.
1.2.13.3.3.
Check the leakages of the lub oil system
Check the damaged seals of the bearing housing
Check the cooler for any leakages
For further service/advice contact………
Water Contamination in lub oil :
1.
2.
1.2.13.3.6.
IGV inoperative
Check inlet/outlet gate
Check other gates/dampers of the gas path
Frequent drop in oil level in the tank :
1.
2.
3.
4.
1.2.13.3.5.
Check the correctness of lubrication. Check oil level, flow,
pressure etc.
Check the functioning of lub oil system and cooling water system
Check the quality and impurities in oil (moisutre/mech impurities)
Check for bearing damages and clearances
Check alignement
Check for any mechanical rubbing
Fans could not be loaded :
1.
2.
3.
1.2.13.3.4.
Check for any looseness of bearing pedestal bolts, impeller hub
bolts, coupling bolts etc.
Check for deposits over the impeller
Check for uneven erosion of the impeller
Check the alignment with the motor
Check for the clearances between rotating and stationary parts
and correct
Check the bearings for any damages. Check the bearing
clearances
Check for any temperature rise of bearings
Carry out vibration analysis to pin-point possible cause
In case of unbalance, carryout balancing to correct the vibrations
Check the cooler of the lub oil system for any leakages
Check for water leakages in the Fan bearings, lub oil tank
Drop in oil pressure :
1.
2.
Check filter elements clean/replace
Check the operation/setting of the recirculation valve/ pressure
relief valves
1.2.14.
Electrostatic Precipitator:
1.2.14.1.
Field Trips on Undervoltage:
1.
2.
3.
4.
5.
6.
7.
8.
1.2.14.2.
Rapping Motor Trips on Overload :
1.
2.
3.
4.
5.
6.
7.
1.2.14.3.
Check for IR value and winding resistance of motor
Check for functioning of Motor & Gearbox after decoupling
Check for alignment of Gearbox with rapping system
Check the rapping shaft alignment during shut down
Check for dislocation of internals
Check for over-filled hoppers
Check for blown fuses, overload relay healthiness in MCC
Heaters are not operating :
1.
2.
3.
4.
1.2.14.4.
Check electronic controller/High voltage rectifier transformer for
Rated Voltage build up on no load
Check the functioning of the Ash disposal system
Check the functioning of collecting & Emitting rapping mechanism
Check for cracks in support, bushing insulator
Check for cracked shaft insulator in shut down
Check for shorting in the field like snapped loose wire in shut
down
Check for overfilled hoppers and distorted emitting system in shut
down
Check for any bent collecting electrodes in shut down
Check for any blown fuse
Check for terminals in MCC/Field JBS for any burnout
Check for any short circuit in heating elements/cables
For further service/advice contact…..
Excessive sparking/flash over in fields :
1.
2.
3.
4.
5.
6.
Check for S&T settings in the Electronic Controller and adjust, if
needed
Check for excessive current settings
Check for any loose connections at transformer HT side, including
disconnecting switch.
Check for snapped emitting electrodes and collecting to emitting
electrodes gaps in shut down
Check the functioning of rapping system
Check the functioning of ash disposal system and overfilled
hoppers.
1.2.14.5.
High Stack Emission :
1.
2.
3.
4.
5.
6.
7.
8.
9.
Check for proper rapping frequency
Check for proper current settings
Check for high flue gas temperature
Check for proper gas flow distribution in the pass during shut
down
Check for eroded guide vanes/splitters during shut down
Check for proper fixing of defector plates of hoppers during
shutdown
Check for proper functioning of ash handling sysgtem
Check for proper fixing of screen plates during shut down
Check for proper closure of manhole doors, inspection doors etc.
to prevent air ingress.
1.2.15.
Water Chemistry :
1.2.15.1.
Phosphate dozing is ineffective in PH control of boiler water:
1.
2.
3.
1.2.15.2.
Phosphate dozing is not reaching drum water :
1.
2.
3.
4.
5.
6.
1.2.15.3.
Check the healthiness of pumps
Check for plugging of piping
Check for proper setting of relief valves.
Check for plugging of nozzles inside the drum
Check for passing of NRV of standby pump.
Check the quality of phosphate
Scales/rust formation over water walls/superheater tubes.
1.
2.
3.
1.2.15.4.
Check the Boiler pressure
Check for phosphate hideout beyond boiler pressure of 180
Kg/Cm2.
Resort to all volatile treatment, taking all precautions
Check for improper water chemistry regime/Improper dozing over
a length of time.
Check the operation of DM plant and quality of DM water
Contact BHEL for remedial actions like chemical cleaning etc
Feed Water/Condensate PH/Conductivity could not be maintained :
1.
2.
3.
Check the quality of Ammonia/Hydrazine
Check for healthiness of pumps and ensure pump is developing
adequate pressure
Check for possibility of leakage condenser tubes.
1.3.
Controls & Insatrumentation (Boiler & Aux.)
1.3.1
FSSS
1.3.1.1
COMMON SYSTEM
1.3.1.1.1
Purging not possible / gets interrupted
1.
2.
3.
4.
5.
Check if any scanners are detecting or are on the verge of
detecting flame.
Check that all fuel valves/gates are closed and correct feedback
is available at the respective panel as well as at the unit panel.
If SADC was in auto earlier, it might have reverted to too low
opening. Confirm its position.
Adjust the air flow suitably and ensure its permissives are
available steadily.
Confirm that the burner tilt is normal (horizontal)
1.3.1.2.
OIL FIRING
1.3.1.2.1
Trip valves not operating
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.3.1.2.2
Check that all permissives are available at the respective panel.
Check the isolating valves feedback.
Check for proper voltages.
Check the healthiness of the coil.
Confirm that no other trip commands (software as well as hardwired)
are present.
Check proper air supply at the field. Ensure that there are no
leakages.
Check the filter and air lock relays.
Check the position of the speed adjusting valve.
Check the solenoid valve for proper port change over.
Check the valve & actuator for leaks, punctured diaphragm,
mechanical obstructions etc.
Oil firing not possible (not taking start).
1.
2.
3.
4.
Check that all permissives are available at the respective panel.
Confirm availability of all panel power supplies.
In case of first guns, check interlocks like nozzle tilt, air flow etc.
Check corner-wise permissives like position of the LGM switch,
status of the limit switches of gun, scavenge valve, oil valve,
manual valves etc.
5.
6.
7.
8.
1.3.1.2.3
Check proper air supply at the corner(s). Check for leakages,
choked filters/ air lock relays, needle valve etc.
Ensure that the scanner of the respective corner is not sensing
flame already.
Confirm at which step the sequence gets interrupted.
Check the suspected valve as in 1.2.1.1 (ii) 5 to 9.
Oil firing not stable.
1.
2.
3.
4.
5.
6.
7.
8.
Confirm the pressure of fuel and atomizing media and the fuel
temperature in case of heavy oils.
Check for restricted opening of the valves.
Check for possible choking of the gun.
Check that scanner supply is ON and settings are in order.
Check the ignitor for proper travel and spark.
Visually check the nozzle and flame from opposite corrner.
Maintain the windbox pressure, differential pressure and proper
opening of corresponding auxiliary damper.
Check the healthiness of the electronic modules and field inputs.
1.3.1.3.
COAL FIRING
1.3.1.3.1
Coal firing not possible(Not taking start).
1.
2.
3.
1.3.1.3.2
Coal firing sequence gets interrupted
1.
2.
1.3.1.3.3
Confirm that the inter panel communication is healthy.
Check all permissives at the corresponding panel (PA permit,
ignition start permit, no protection trip, closed status of all PA
dampers, brake position, luboil protection etc)
Confirm that start command is issued from the panel.
Confirm how far the start sequence proceeds and where it gets
blocked.
Check the interlocks of individual steps.
Coal firing not stable / trips frequently.
1.
2.
Identify the cause of trip and the individual cause as per
appropriate check list.
If the indicated cause appears spurious / unreasonable,
check for healthiness of control panel cards , communication and
data integrity.
1.3.1.3.4
Trips on ignition energy / flame failure
1.
2.
3.
4.
5.
1.3.2
Check that PA pressure is maintained.
Confirm that sufficient ignition support is available.
Confirm that scanners are all in service and detect a reasonable
level of flame.
Confirm the frequency setting of the fire ball scanners are as per
recommendation.
Check the SADC for proper damper position.
1.3.2.
SECONDARY AIR DAMPER CONTROL (SADC)
1.3.2.1.
No output from the panel.
1.
2.
3.
1.3.2.2.
Output not varying.
1.
2.
3.
4.
1.3.2.4.
Check the signal to the output cards separately and establish it.
Check the output cards separately.
Check the field cabling for earth faults, short circuits and proper
polarity.
Check for any overriding protective interlocks ( e.g, ID-FD fans
off, MFT, furnace to WB DP high.)
Damper opening not matching with the demand
1.
2.
3.
4.
5.
6.
7.
8.
9.
1.3.2.5.
Check the control panel for proper functioning.
Check the power supply and the healthiness of cards in the panel.
Confirm data transfer between console, I/O cards and processor.
Ensure correct air supply to the I/P (current to pressure )
transmitters.
Check the cabling for polarity, healthiness of connections
Check the current input and signal output at the I/P outlet port.
Check the signal tubing for leakages. Conduct pressure decay
test if doubt persists.
Check the damper separately for mechanical freeness.
Check the power cylinder air supply for proper quality and
pressure.
After ensuring proper signal and power air supplies to the
actuator,
check its response (output air pressure).
Check the setting of the air lock relay on the actuator.
Service the actuator.
Failure of Auto control of Auxiliary damper
1.
2.
3.
4.
5.
6.
7.
1.3.2.6
Failure of Fuel air dampers.
1.
2.
3.
4.
1.3.2.7
Check the furnace to WB diff pressure transmitters for proper
functioning.
Check for high mismatch between measured
values.
Confirm that ALL the dampers are responding properly and the
damper position in all corners of the same elevation are matching.
Check the response of the DP when dampers are manually
adjusted.
Adjust the bias to get suitable DP demand.
Check the healthiness of reference signal used to generate DP
demand ( boiler load index)
Check for any over riding interlocks.
Check the secondary air system for proper status.
Check that no override commands are present.
Check that the reference input ( e.g PA flow) is OK.
Check the damper operation in manual.
Tune the parameters to suit the firing regime.
Failure of Over fire dampers
1.
2.
3.
4.
Check that no override commands are present.
Check that the reference input ( boiler load) is OK.
Check the damper operation in manual.
Tune the parameters to suit the firing regime.