boiler emergancy
Post on 05-Apr-2018
216 Views
Preview:
TRANSCRIPT
-
8/2/2019 Boiler Emergancy
1/35
-
8/2/2019 Boiler Emergancy
2/35
HANDLING OFBOILERDURINGEMERGENCIES
-
8/2/2019 Boiler Emergancy
3/35
BOILER EMERGENCIES
1)ONE ID FAN TRIPPED
2)ONE FD FAN TRIPPED
3)BOTH ID FANS TRIPPED
4) BOTH FD FANS TRIPPED
5) ONE PA FAN TRIPPED 6) BOTH PA FANS TRIPPED
-
8/2/2019 Boiler Emergancy
4/35
7) COAL MILL TRIPPED
8)DRUM LEVEL VERY LOW
9)DRUM LEVEL VERY HIGH
10) ONE BFP TRIPPED
11)BOTH BFP TRIPPED 12) FURNACE DRAFT VERY LOW
13) FURNACE DRAFT VERY HIGH
-
8/2/2019 Boiler Emergancy
5/35
-
8/2/2019 Boiler Emergancy
6/35
HANDLING OF BOILER DURING EMERGENCY
EMERGENCY OPERATIONS
Major emergency situations in Boiler and
Auxiliary areas and suggested actions:
1. High Furnace Pressure
Probable Reasons:
One I.D. fan tripped or maloperation of control
vanes of I.D,F.D,P.A. fans or closing of damper.
Unstable furnace flame condition, Sudden
starting of coal mill, Low windbox pressure
nder normal F.D. fans loading conditions),
proper air distribution at elevations.
Un-equal burner tilts at corners or Burner tilt in
extreme up or Down.
Fouling in Air heater, Air heater tripped.
Furnace water seal broken, ES.P. or flue gas path
manhole opened.
Water wall tube rupture/leakage.
-
8/2/2019 Boiler Emergancy
7/35
-
8/2/2019 Boiler Emergancy
8/35
Action to be taken:See that two mills are tripped or
otherwise trip them.Take running I.D. fans control onmanual & increase for loading. Checkthe cause of I.D. fan tripping and try torestart it, if everything is normal. Checkgas dampers indication & draft readingalong flue gas path. If some damper isclosed try to open that damper.
Take F.D. / P.A. fan control onmanual. Check control damperoperation. Adjust air flow.
-
8/2/2019 Boiler Emergancy
9/35
Action to be taken:Check air for correct flow. Check com bustionregime, openings of Auxiliary air and fuel airdam pers. wind box p ressure. See cold air andhot air dampers. Watch Furnace flame. TripBoiler if flam e is very much unstable. Purge outexplosive m ixture by maintaining h igh air flow .
Check Burner tilt at all corners is equal.Adjust Burner tilt between + 10 to -10 andcheck control air pressure.
See air-preheaters are rotating. Restarttripped air preheater and do A .H. soot blowing.
Check Furnace seal, water flow through sealtrough overflow. Re-establish seal.
Stop the boiler in case of tube leakage assoon as possible.
-
8/2/2019 Boiler Emergancy
10/35
2. Furnace Pressure LowProbable Reasons:
I.D. fan auto control
failure. I.D. fan vane controlmechanism failure causingvanes to open wide
Sudden decrease in airinput or tripping of one F.D.fan.
Sudden tripping of one ormore mills or choking of
mills/raw coal feeder pipe .
Partial flame failure
-
8/2/2019 Boiler Emergancy
11/35
Action to be taken
Take I.D. fans control on manual &reduce load on I.D. fans
Check I.D. fan control mechanism forproper functioning.
Check air flow, correct if necessary. Afterchecking restart F.D. fan if it had tripped.
Control the furnace pressure by adjustingI.D. fan vanes. Simultaneously try standbymill. Remove the choking of affected mill /Raw coal feed pipe.
Take the oil gun i.nto service to establishflame that locations / corner.
See the proper functioning of secondary airpath damper.
l
-
8/2/2019 Boiler Emergancy
12/35
3. Drum Level Low
Probable Reasons:
Mal-operation of Feed Auto Control or
Feed Regulator or Scoop auto.
Tripping of one of working feed pump
(standby pump does not start).
Sudden reduction of load.
Sudden increase in firing e.g. starting of
mills having sufficient coal left before
previous stopping.
Tube rupture/puncture.
Inadvertent opening of low point drain
valves or Emergency drum drain valve.
A i b k
-
8/2/2019 Boiler Emergancy
13/35
Action to be taken:
Take feed control valve on
manual and increase feeding
rate. Take scoop tube controlon hand increase scoop tube
position.
Check that water flow through
each pump does not exceed
capacity. Check feed watercontrol valve and tube control
linkages.
Starts reserve feed pump on
tripping of running feed pump,if auto starting fails.
Try to increase the load if not
possible, reduce firing rate
accordingly to control drumpressure.
A ti t b t k
-
8/2/2019 Boiler Emergancy
14/35
Action to be taken:
Reduce firing rate by suitablyadjusting the feed rate ofrunning mills. Check water flow andcompare with previous feedingrate and steam flow. High feedflow indicates tube failure.Inspect waterwall and
economizer or any tubeleakage,If tube leakage observed stopthe boiler as soon as possible,. Check drum drains and, low
point drains for closing.
Note: If drum level goes belowgauge glass and low drum leveltrip protection fails, trip boiler
at on low level.
-
8/2/2019 Boiler Emergancy
15/35
4. High Drum Level
Probable Reasons:
Mal-operation of feed watercontrol
Sudden increase in load
resulting in drum pressuredrop.
Sudden decrease in firing
rate e.g. tripping of the
running mills . B.F.P. scoop
tube position suddenly
increased
A ti t b t k
-
8/2/2019 Boiler Emergancy
16/35
Action to be taken:
Take feed control valve on
manual and reduce feedingrate.
Try to decrease the load as
far as possible.
Increase feeding range of
running mills.
Check differential pressureacross feed control valve and
maintain 5 Kg / cm2 by
adjusting scoop tube position.
5 Flame Failure At anElevvation
-
8/2/2019 Boiler Emergancy
17/35
5. Flame Failure At anElevvation
Probable Reasons:
Closing of trip valves on H.O./ W.U. Oil
/ Igniter (Causing loss of ignitionsupport energy) Where F.O. is beingused as support fuel or when only oil isbeing used.
Sudden decrease of mill feeder speedsto minimum.
Too low or too high windbox pressurecausing unstable combustion.
Water wall tube failure.
Malfunction of flame scanners due to
supply failure or scanner air failure, slagor soot onscanner lenses etc.
Burner tilt mechanism negativeextreme due to air failure to powercylinders.
Rapid load changes without adjusting
airflow leading to improper combustion.
Action to be taken
-
8/2/2019 Boiler Emergancy
18/35
Action to be taken:
Do not attempt to introduce igniters oroil guns at elevation where No flamecondition persist.
Trip out the coal mills of feedingelevation where No flame conditions ispersisting. Allow sometime for purgingthen introduce oil support adjacent toworking mills until furnaceflame is stabilized.
Check that secondary air wind boxdampers are modulating to maintainabout 80m.m.wcwind box to furnace differentialpressure.
Check furnace for tube failure.
If two elevations scanners show Noflame trip the boiler manually
Check burner tilt keep it between /+10 .
Check furnaces flame condition.
-
8/2/2019 Boiler Emergancy
19/35
6.0ne Fan Trips (Other in Service)
Probable Reasons:
It Is presumed that ID, FD, PA
fan de-interlocking switches areon Interlock position.
Fan Bearing temperature, highand/or
Fan motor Bearing temperaturehigh and/or
Lube oil pressure for motorbearings low and/or
Corresponding Air heatertripped (provided de-inter lockingswitch is on Interlock position)and/or.
Motor protection operated.
Action to be taken
-
8/2/2019 Boiler Emergancy
20/35
Action to be taken:
Takes draft control or manual, and / orincrease the loading on running fan and
maintain furnace draft.
Check corresponding fan is trippedthrough interlock.
Take secondary airflow controls onmanual and maintain correct airflow.
Cut in oil burner adjacent to workingmills. .
Check drum level is controlled on autoif necessary, take drum level control On
manual and maintain level.
Check pulverizers in excess of 3 aretripped starting from bottom.
Check that the load on the generatorhas reduced to 100 - 120 MW (partial
load relay energized).
-
8/2/2019 Boiler Emergancy
21/35
Check that interconnecting
dampers on air and flue gas side
open and tripped fans are
correctly isolated through
interlocks.
Check windbox pressure left and
right is maintained normal (about
75 mmwc).
Maintain steam temperature.
Check furnace flames condition.
Check that tripped pulverizers
are correct isolated (hot air gatesclose, cold air dampers come to
minimum).
Investigate the cause of trip.
Correct it & restart the tripped fan.
-
8/2/2019 Boiler Emergancy
22/35
7. One Feeder Trips
Probable Reasons:
Support energy is removedwithin 3 minutes of feederand/or.
No. coal flow alarm comes& low current relay picks upsimultaneously. (Feeder
shear pin given way) and/or.
Mill trips and/or.
Feeder motor supply fails.
-
8/2/2019 Boiler Emergancy
23/35
Action to be taken:
Check that hot air gate closes & cold air
damper opens full if pulverizer is running.
Clear the mill of the coal before stopped.
Stop the pulverizer if feeder cannot be
restarted immediately.
Check that running mills share the loading,
thermal load is on auto.
Reduce the load on generator and, maintainsteam parameters.
If 3 mills at less than 50% feeder speed or
2 mills are left in service, cut in oil gun
adjacent to working mills.
Check furnace draft, airflow and drum level
is normal.
Check flame is stable and scanners sense
Flame on.
Check that associated elevation fuel air
damper close and windbox pressure is
maintained 70 mmwc.
-
8/2/2019 Boiler Emergancy
24/35
8. One Mill Trills
Probable Reasons:
Mill discharge valves areclosed and/or
Loss of elevation D.c.supply for more than 2 secs
and lor
Support ignition energy isremoved with 3 minutes offeeder starting and / or .
Motor protection operatesand / or
One P.A. Fan trips (mill inexcess of 3 will trip starting
from bottom).
-
8/2/2019 Boiler Emergancy
25/35
Action to be taken:
Check the running mills sharethe load if thermal load control ofmills is on auto.
Reduce the generator load ifpressure starts dropping.
Start reserve mill and take load.
Check furnace draft is maintainenormal.
Check the correct airflow ismaintained.
Check that drum level ismaintained normal.
Check that tripped mill isisolated (hot air gate closed, coldair damper minimum open,feeder tripped).
-
8/2/2019 Boiler Emergancy
26/35
9. Hang-up in Mill
Probable Reasons:
Choking of coal atinlet to mill. H-ighmoisture in coal and /
or
Too much fineness incoal with moisture and/ or
Foreign material atRC feeder inlet
Action to be taken
-
8/2/2019 Boiler Emergancy
27/35
Action to be taken:
Check feeder trip on No Coal
flow & low current protection.
Check mill outlet temperature
is less than 85C.
Check mill hot air gate closes
on mill outlet temperature high
protection. Close hot air gate
and check mill.
Cold air damper opens full.
Check the flame condition at
the sick mill elevation.
Trip the sick mill after
clearing it coals.
-
8/2/2019 Boiler Emergancy
28/35
Increase the load on
running mills if the thermalload control is on manual.
Start reserve mill.
Maintain steam pressure
and temperature by reducing
load.
Check that furnace draft
and airflow are normal.
If 3 mills (or less) are inservice with speed below
50% take oil support atelevation adjacent to running
mills in service.
-
8/2/2019 Boiler Emergancy
29/35
10. Water Wall Tube Leakage
Probable Reasons:
Starved water walls due to very
low drum level and/or
Sustained flame impingementon water wall tubes and / or
Blocked tube, scaling of tube,
resulting in overheating of tube
Metal, pitting, corrosion of tubesand/or
Soot blower steam impingement
(wet steam impingement or directimpingement of steam)and/or
Circulation affected due toopening of low point drains.
Action to be taken:
-
8/2/2019 Boiler Emergancy
30/35
Action to be taken:
Compare feed water flow andsteam flow, assess the
magnitude of tube leakage.
Maintain drum level byincreasing feed water flow.
Inspect the furnace for tubeleakage.
If the tube leakage is minutethen take the unit out as a
planned shutdown to cold.
If tube leakage is heavy & itis likely to damage other tubesor likely to disturb the flame
stability trip out the unit.
-
8/2/2019 Boiler Emergancy
31/35
Keep close watch in
furnace flame.
As the load is beingreduced try to locate
burst tubes.
Check economizer
hoppers for water
leakage steam noise
etc. every shift.
Check that furnace
draft is maintained
normal.
11 Reheater /SuDerheater /
-
8/2/2019 Boiler Emergancy
32/35
11. Reheater/SuDerheater /
Economizer Tube Failure
Probable Reasons:
Sustained high metaltemperature due to waterwall
Slagging or forcing boiler at the
time of hot restart and / or
Erosion on tubes due to highexcess air, high ash content in
coal, dislocated tubes, soot
blowing and/or
Blocked tubes causingoverheating and/or
S lt d iti d t hi h
-
8/2/2019 Boiler Emergancy
33/35
Salt deposition due to high
water level in drum. poor
quality of water and/or
Inadequpte flow due to open
Superheater, Reheater drain
and / or
Fire side corrosion of tubesand / or
Economizer tube can fail due
to over heating if concentrationof Fe, Cu is more in feed water,
Steaming in economizer occurs
causing salt deposition and
harming the tubes.
-
8/2/2019 Boiler Emergancy
34/35
Action to be taken:
As soon as leakage isdetected start load
reduction and trip out
the boiler at theearliest possible time.
Try to locate leakthrough manholesbefore boiler isdepressurized.
-
8/2/2019 Boiler Emergancy
35/35
top related