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Satisfactory Boiler start up
Start up of individual oil system AB/CD/EF
Operation of fuel firing subject to certain conditionsA/B/C/D/F
Protection and interlock of oil /Coal System
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Typical Graphic Display of fuelfiring
244 subscriptions (requests)
for data from the DPU.
75 maxSCRIPTS
30 Buttons
29 List Controls
3 Bar Charts
14 Text State controls
45 objects have dynamicborders
200K of various static bitmaps
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The boiler can be placed in service, initially orafter a Master Fuel Trip, in the following
sequence through FSSS.
Furnace Purge
Before any fuel firing can takes place, initially or
following a boiler trip, a satisfactory PurgeCyclemust be completed.
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Initially, the Heavy Oil must be recirculated andheated to obtain the proper temperature and
viscosity for efficient combustion. After this is
accomplished, the Heavy Oil Trip Valve (HOTV)
can be closed and then the furnace purge
cycle can be started.
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After the furnace purge cycle is completed, the heavy oil
elevation (AB, CD, EF, & GH) can be taken into service. Anoil elevation is said to be InService, when at least three
out of four heavy oil nozzle valves are open and the flame
is sensed by the scanners.
After the heavy oil elevation is in service, either of the
adjacent coal elevation can be taken into service because
IgnitionPermit is now available for starting the pulverizer.
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A Coal elevation is said to be In Service after
the Pulverizer is ON, its Hot Air Gate (HAG) is
open and the associated Feeder is proven (i.e.,
feeder ON for more than 50 seconds). A fireballsignal is established when the associated fireball
flame scanner senses flame and ELEVATION
FLAME indicator is illuminated on the FSSSconsole in control room.
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Boiler purge operation
Start up of oil firing(AB,CD,FH & GH)
Adequate Ignition permit
Firing of coal elevation(A,B,C,D,E,F,G & H)
Flame sensing by scanners.
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FSSS LOGIC
FSSS logics can be broadly divided
into 3 sections.
Unit Logic.
Oil Elevation Logic.
Coal Elevation Logic
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Boiler purge logic
Master fuel trip logic
Oil trip valve operation logic
PA Fans logic
Scanner air Fans logic
Seal air Fan logic
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FURNACE PURGE
Purpose::Complete Removal of unburnt fuel from entire furnace
Procedure: Ensure that all fuel to furnace is cut off and all flame is out Provide adequate air flow through furnace (30 to 40%) Initiate a MANDATORY purge time cycle (9 min)
Consequence: Master Fuel Trip Relays are reset Firing of fuel into the furnace is allowed
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Boiler purge logic, which ensures a
fiveminutes purge cycle is completed
before any fuel firing can take place.
A PurgeReady signal at control room
will be available when all the following
conditions are satisfied:
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All HFO nozzle valves are closed
All Pulverizers are off
No MFT condition present
All feeders are off All scanners sensing no flame.
All auxiliary air dampers modulating
Both PA fans off
All HAGs closed Air flow more than 30% and less than 50%
HFO trip valve is closed
Wind box to furnace DP is adequate.
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TOFSSS
All HFO nozzle valves closed
All pulverisers OFF
All feeders OFF
No MFT condition present
All scanners senses no flame
All Auxiliary Air dampers modulating
Both PA fans OFF
All Mill HAGs closed
Air flow more than 30% and less than 50%
HFO trip valve is closed
Wind box to furnace DP is adequate
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MASTER FUEL TRIP (MFT) MFT or Boiler Trip means:
Complete isolation of all fuel to furnace under certainconditions
Automatic Procedure:
All oil valves are given closing command
All mills and feeders are given trip command
All Primary Air (PA) Fans are given trip command
All Hot Air Gates (to mills) are given closing command
Further Consequences: Turbine protection is initiated (to trip turbine) All SH and RH spray valves are given closing command
All elevation SADC are given full open command
Furnace pressure & Air flow controls are set to manual
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This ensures a safe shut down of the boiler in case
of any abnormal conditions in boiler/ furnace. Ifsome abnormal condition occurs, Master Fuel TripRelay acts and ensures the closure of Heavy OilTrip valve (HOTV) and all Oil Nozzle Valves (ONV),
thus cutting off total oil supply. It also ensures thestopping of all pulverizer systems and Primary Air(PA) fans, cutting off total coal supply to boiler. Thevarious abnormal operating conditions under which
Master Fuel Trip occurs are as follows:-
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Both FD fans OFF
Both ID fans OFF. Inadequate water wall circulation for more than 5 seconds.
Loss of Reheat Protection for greater than 10 seconds. All BFPs tripped. Drum level very high for more than 10 seconds (2/3 logic) Drum level very low for more than 10 seconds (2/3 logic)
Furnace pressure very high (2/3 logic) Furnace pressure very low (2/3 logic) Loss of all fuel. All feeders OFF and loss of AC Supply to the elevation in service.
Unit flame failure.
Loss of Unit Critical Power for more than 2 seconds Both Secondary APHs OFF.
Loss of 220 V DC Supply for more than 2 seconds. Air flow less than 30% and boiler load not greater than 30%. Manual Emergency trip.
B h FD f OFF
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Both FD fans OFFBoth ID fans OFF
MFTRELAY
Air flow less than 30% and boiler load not greater than 30%
Loss of 220 V DC Supply for more than 2 seconds
Manual Emergency PB trip
Both Secondary APHs OFF
Loss of Unit Critical Power for more than 2 seconds
Unit flame failure
All feeders OFF and loss of AC Supply to the elevation in service
Loss of all fuel
Furnace pressure very low (2/3 logic)
Furnace pressure very high (2/3 logic)
Drum level very low for more than 10 seconds (2/3 logic)
Drum level very high for more than 10 seconds (2/3 logic)
All BFPs tripped
Loss of Reheat Protection for greater than 10 seconds
Inadequate water wall circulation for more than 5 seconds
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Trips all mills
Trips all feeders
Trips PA fans
Closes HFO trip valve
Closes all elevation nozzle valves
Close all HAGs
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This logic ensures that oil trip valve can be opened
after the purge cycle is completed and no MFTcondition is present, if the following conditions are
also satisfied.
All nozzle valves are closed.
HFO supply pressure is satisfactory.
HFO header temperature is satisfactory. Similarly, this logic ensures the closure of oil trip
valve in case of MFT.
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It monitors the scanner air duct to furnace DP
and ensures starting of scanner air fan - A or incase it fails to start, scanner air fan - B. Thislogic gives an open command to scanner fanoutlet damper after starting the fan.
Also, in case of both FD fans not running, itensures the scanner air emergency damper is
open.
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Monitors seal air header to cold air duct DP
and ensures the starting of seal air fan - A or
B ( in case A does not start), provided at least
one PA fan is running.
Gives an open command to seal air fandischarge damper once fan starts.
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Oil Elevation Logic
AB/CD/EF/HJ*
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Start of oil elevations AB,CD,EF and GH
Sequential operation with start command
Corner1,corner3,corner2 and corner4
Gun advance,igniter advance
Spark,atomizing valve open,oil valve open
Sensing of discriminatory flame
Retract of igniter
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Stop of oil elevation
Closure of oil valve,opening of scavenge valve
Igniter advance and sparking
Closure of atomizing valve and scavenge valve
Retract of igniter and gun
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OIL ELEVATION LOGIC
There are four heavy oil elevations AB, CD, EF & GH. Forall these elevations, logics are same. Oil elevation can be
placed in service auto/manual. For a particular elevation,
only one command is given for all the four corners together.
(e.g. One common start command for elevation AB-1, 2, 3and 4 guns). But start command goes to corners 1 to 4
sequentially. First command goes to corner 1; after 15
seconds start commend goes to corner 3; again after a
lapse of 15 seconds start commend goes to corner 2; and
again after a gap of 15 seconds start command goes to
corner 4.
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The sequence of operation taking place for a particular oil gun once thecommand is given is as follows:-
First the oil gun is advanced. Once gun advanced feedback is available the HEA igniter is advanced. Then atomizing steam valve is opened for the particular corner. Then HFO nozzle valve gets open command.
Spark command is given to igniter transformer, thus producing a spark at
the spark tip. Then for this particular corner HFO flow satisfactory feedback comes
from the flow switch in the oil line. The corner oil gun proves when the DISCR FLAME SCANNER senses
FLAME.
When 25 seconds elapses after oil valve open, igniter spark signal is
removed and spark rod is retracted. If the corner oil gun did not prove FLAME by this time, Oil nozzle valve
and atomizing steam valve closes. Gun and igniter are retracted.
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OIL FIRING PERMISSIVE-
1-PURGE COMPLETE/MFT RESET AND NO FIRST
UP FAULT.2- HFO PR. OK >25 KSC.3- HFO TEMP OK >95C4- IGNITOR AIR PR. >200 MMWG.5- IGNITOR OIL PR. >10 KSC.
6- NO LIGHT UP IN PROGRESS.7- NO BURNER START INHIBIT.8-PERMISSIVE TO FIRE OIL.
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OIL BURNER START LOGIC
*OIL BURNER START PUSH BUTTON (NO
OTHER OIL BURNER START IN PROGRESS).
OIL BURNER START SEQUENCE-
1-OIL BURNER SEC. AIR DAMPER OPENED.2-OPEN IGNITER OIL MASTER TRIP VALVE.3-NO FLAME SENSED IN LAST 5 SEC.4-ENERGISE IGNITOR TRANSFORMER.
5- OPEN IGNITOR OIL SOLENOID V/V.6- DETECT IGNITION OIL FLAME.7- 4 WAY V/V TO FIRING POSITION.8- OIL FLAME DETECTED.
9-CLOSE IOTV/SOL. V/V.
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Coal Elevation Logic
A/B/C/D/F
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Pulverizer start logic
Availability of PA permit
Availability of ignition permit
Seal air /bowl differential pressure
No MFT
Lube oil pressure adequate
Pulverizer stop logic
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Feeder start logic
Pulverizer on
Outlet temperature adequate
Speed demand minimum
No MFT
Feeder stop logic
Had/cad logic
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COAL ELEVATION LOGIC
PULVERISER LOGIC
This logic takes the count of total no. of pulverisers in
service at any point of time, the no. of FD Fans andPA fans in service. With PA Fan ON and PA HeaderPressure adequate (>560 mmwcl), it gives PApermit to start the Pulverizer. In case of PA Header
Pressure going low-low or PA/ FD fans trips, itensures the shut down of Pulverizers from topelevation to bottom elevation in a timed sequence.
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Each mill can be taken in to service manually or
automatically. Auto manual selection push button
is available on FSSS console for each mill.
Initially, Pulverizer Ignition Permit signal mustbe established for the mill to start. Other condition
required to be established for starting the mill are
as follows:-
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INTERMEDIATE OIL BURNERELEVATION FIRING
OR
30% BOILER LOAD
ADJACENT MILL FIRING
PA FAN IN SERVICE
AND
AND
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Mill lub oil pressure adequate.
Start permit from FSSS.
Mill Discharge valve open.
Mill outlet temp. > 93OC.(200OF)
Cold Air Gate (CAG) open.
Tramp iron vale (Top Reject Gate) open.
Feeder inlet gate open.
Seal air DP adequate (200 mmwcl).
Feeder local switch in remote.
Once the mill is ON, associated HAG can be opened
and feeder can be placed in service.
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OIL BURNER FIRING ON MILL BEING BROUGHT
INTO SERVICE-
FOR ANY MILLS(A,B,C,D,E,F,G,H)1-AT LEAST THREE OIL BURNER S FIRING IN SELECTED
ELEVATION.
2- (A) BOILER LOAD > 30% BCMR
AND(B) UPPER OR LOWER ADJACENT COAL BURNER IN
OPERATION
EXAMPLE: FOR MILL A START PERMISSIVE:1- ELEVATION AB 3/4 OIL BURNER FIRING.
OR2- MILL B FIRING
ANDBOILER LOAD >30% BCMR.
O
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FOR B,D,F MILLA) AT LEAST 3 OIL BURNERS FIRING IN THE BURNER
GROUP ABOVE
AND(B) ADJACENT COAL BURNER ABOVE IN OPERATIONAND
(C) THIS ELEVATION IS HIGHEST IN THE BURNER GROUP
EXAMPLE- FOR MILL B START PERMISSIVE-
(1) ELEVATION AB 3 / 4 OIL BURNER ARE I/ S .
OR(2) MILL A FIRING OR MILL C FIRING
AND
BOILER LOAD > 30% OF BCMR.OR
(3) MILL C FIRING
ANDELEVATION CD 3 / 4 OIL BURNER ARE I/S.
* NOTE THAT B ELEVATION IS HIGHEST IN THE BURNER GROUP AB.
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FOR MILL C,E,GA) AT LEAST 3 OIL BURNER FIRING IN THE BURNER GROUP BELOW.
AND
(B) ADJACENT COAL BURNER BELOW IN OPERATION.AND
(C) THIS ELEVATION IS LOWEST IN THE BURNER GROUP.
EXAMPLE- FOR MILL C START PERMISSIVE (1) ELEVATION CD 3 / 4 OIL BURNER I/S.
OR(2) MILL B FIRING OR MILL D FIRING
ANDLOAD > 30% OF BCMR.
OR(3) MILL B FIRING
ANDELEVATION AB 3 / 4 OIL BURNER ARE I/S.
* NOTE THAT C ELEVATION IS LOWEST IN THE BURNER GROUP CD
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30% BOILER LOAD
ADJACENT MILL FIRING
PA FAN IN SERVICE
INTERMEDIATE OIL BURNERELEVATION FIRING
ANDOR
AND
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IT WILL NEVER OCCUR FOR THE FOLLOWING
CONDITION-(1) IF THREE OR MORE MILLS FIRING THEN PARTIAL FLAME
FAILURE WILL NEVER EXISTS.
(2) IF LESS THAN THREE MILLS ARE FIRING THEN PARTIALFLAME FAILURE DOES NOT EXISTS IF MILL WHICH ISFIRING HAVE THE MILL PERMISSIVE FOR FIRING.
IT WILL OCCUR WHEN THIS LOGIC SATISFY-
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VOTING OF ELEVATION
VOTING IN AB ELEVATION WILL BE AVAILABLE
(1) MILL A FEEDER OR MILL B FEEDER I/S.
ANDELEVATION AB 2 / 4 FLAMES IN.
INTRLOCKED WITH ( ALL BURNER IN AB ELEVATION
SATISFACTORY S/D OR 3 / 4 OIL BURNER IN THAT ELEVATION
ARE I/S.)
(2) VOTING IN BC ELEVATION WILL BE AVAILABLE-
MILL B FEEDER OR MILL C FEEDER I/S.AND
ELEVATION B 2 / 4 FLAMES IN.
VOTING WIL NOT BE AVAILABLE (1) BOTH FEEDERS ON BURNER ELEVATION ARE NOT I/S.
OR
(2) 2/4 FLAME ARE NOT SENSED INTERLOCKED WITH 3 / 4 OILBURNER ARE NOT FIRING.
OR
(3) OIL GUN IN THAT ELEVATION NOT SATISFACTORLY
SHUTDOWN INTROLOCKED WITH 3 / 4 OIL BURNER IN THAT
ELEVATION NOT FIRING.
Feeder start Logic
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Feeder start Logic
Feeder start command is given from FSSSElevation Logic only. This command is
continuously required to keep the feeder in
service. Feeder speed demand minimum,Pulverizer ON, pulverizer outlet temp > 130OF,
HAG open and no MFT are the important
conditions required to give the feeder start
command from FSSS.
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In case of pulveriser power high, bowl DP High or
feeder OFF command, feeder speed demand is
driven to minimum.
Release feeder to Auto Signal is also coming from
FSSS. All of the above conditions are present and
feeder is not ON for more than 50 seconds, release
signal for auto is available.
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