02 FSSS Logic System

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24 May 2012 PMI Revision 00 1


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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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Documents

02 FSSS Logic System