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FURNACE SAFEGUARD SUPERVISORY SYSTEM
 F.S.S.S. facilitates remote manual/automatic control of fuel
firing equipments through mechanized system and
suitable interlocks/logics.
 It is designed to ensure the execution of a safe, orderly
operating sequence in start up and shutdown of fuel firing
equipments and to prevent errors of omission in following
such a safe operating procedure.
 The system provides protection against malfunction of
fuel firing equipment and associated air system.
 The safety feature of system are designed for
protection in most common emergency situations.
F .S.S.S. Equipment can be grouped under three heads
1.
The Operating and Indicating Console
 This consists of all switches for initiating controls and also
indications of status of all fuel firing equipment & their auxiliaries.
2.
Relay and Logic Cabinets:
 The cabinets consists of relays, timers, programmers, circuit
breakers for AC and DC control suppliers flame scanner unit,
number of coal flow units etc. They control the process logic
Field Equipments
 Field equipments are those which help in actual remote operation of fuel firing
equipments and those which provide the status to the operating console and
relay logic cabinet.
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Ignitor/H.O Trip Valves,
H.O atomizing steam,
Scavenging atomizing nozzle valve (Hydramotor type),
Gun advance/retract mechanisms,
Oil gun assembly,
Ignitors and its cabinets,
Flame scanner and ignitor air fans,
Pressure switches, temperature switches, flow switches and limit switches,
Mill Discharge valves, hot air gates, sealing air valves, cold air, tramp iron gate
etc.
Functions of FSSS
 To start complete furnace purge when all technological conditions are
fulfilled.
 To start and monitor ignitors
 H.O. guns, (oil guns) starting, stopping and supervision.
 Pulveriser and feeder starting, stopping and supervision
 Flame scanner intelligence and checking.
 Furnace flame monitoring and overall furnace flame failure protection.
Functions of FSSS
 To start-stop igniter and scanner air fans.
 To effect secondary air damper control with indication of
auxiliary and fuel air damper modulation/close.
 To trip out all boiler fires when boiler safety is threatened
 To provide boiler trip signal to other equipments such as P
.A. Fan, Turbine, Generator etc.
• BURNER
MANAGEMENT
SYSTEM
• BOILER
PROTECTIONS
• MILLING
SYSTEM
• FUEL OIL
SYSTEM
• UNIT PURGE
• SEC. AIR DAMPER • AUX. PRDS
CONTROL
CONTROL
• SOOT BLOWER
CONTROL
• HP-BYPASS
CONTROL
FUEL
V/V
AIR
DAMPER
LOCAL
CONTROL
BOX
FLAME
DETECTOR
IGNITER
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IGNITION
CONTROL
PANEL
B
M
S
DAS
MILL
CONTROL
BOILER
PLANT
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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
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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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PURGE PERMISSIVES
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
TO
FSSS
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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Purge Logic
AIR DAMPERAIR DAMPER ARE DIVIDED AS FOLLOWS1-FIVE ELEVATION OF FOUR SECONDARY AIR.
2- 4 ELEVATION OF 4 AIR TO OIL/S.A.D
3-8 ELEVATION OF 4 AIR TO P.F. BURNER.
4-TWO ELEVATION OF FOUR OVERFIRE AIR.
BURNER
GROUP
NUMBER
4
3
2
1
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NOZZLE
ELEVATION
NUMBER
NOZZLE
TYPE
MILL GROUP
GROUP
13---------------------------SECONDARY AIR
12---------------------------COAL--------------------------- -F
11---------------------------OIL AND S/A
10 --------------------------COAL-----------------------------E
9 --------------------------SECONDARY AIR
8---------------------------COAL------------------------------D
7-------------------------- OIL AND S/A
6---------------------------COAL------------------------------C
5---------------------------SECONDARY AIR
4---------------------------COAL------------------------------B
3---------------------------OIL AND S/A
2---------------------------COAL------------------------------A
1-------------------------- SECONDARY AIR
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Oil Trip Valve operation logic

This logic ensures that oil trip valve can be opened after
the purge cycle is completed and no MFT condition 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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OIL ELEVATION LOGIC

There are four heavy oil elevations AB, CD, EF & GH. For all
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, 3 and 4 guns).

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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Oil elevation logic
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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Oil elevation logic
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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A particular corner takes the start command only
if the following conditions are satisfied: The particular corner oil gun engaged feedback is
available.
 The steam scavenge valve is closed for the particular
corner.
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The sequence of operation taking place for a particular oil gun once the
command 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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Scanner air fans logic

It monitors the scanner air duct to furnace DP
and ensures starting of scanner air fan - A or in
case it fails to start, scanner air fan - B. This logic
gives an open command to scanner fan outlet
damper after starting the fan.

Also, in case of both FD fans not running, it
ensures the scanner air emergency damper is
open.
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Seal air fans logic

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 fan
discharge damper once fan starts.
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Coal elevation logic
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
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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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 and PA fans
in service.
 With PA Fan ‘ON’ and PA Header Pressure adequate (>560
mmwcl), it gives “PA permit” to start the Pulverizer.
 In case of PA Header Pressure going low-low or PA/ FD
fans trips, it ensures the shut down of Pulverizers from top
elevation 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 must be established
for the mill to start. Other condition required to be
established for starting the mill are as follows:-
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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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30% BOILER LOAD
AND
ADJACENT MILL FIRING
OR
INTERMEDIATE OIL BURNER
ELEVATION FIRING
AND
PA FAN 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.
OR
2- MILL B FIRING
AND
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BOILER
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LOAD >30%
BCMR.
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FOR B,D,F MILL
(A) AT LEAST 3 OIL BURNERS FIRING IN THE BURNER
GROUP ABOVE
AND
(B) ADJACENT COAL BURNER ABOVE IN OPERATION
AND
(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
AND
ELEVATION 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,G
(A) 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
AND
LOAD > 30% OF BCMR.
(3)
MILL B FIRING
OR
AND
ELEVATION AB 3 / 4 OIL BURNER ARE I/S.
* NOTE THAT C ELEVATION IS LOWEST IN THE BURNER
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GROUP CD
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Flame Scanners
VOTING OF ELEVATION –
VOTING IN AB ELEVATION WILL BE AVAILABLE
(1) MILL A FEEDER OR MILL B FEEDER I/S.
AND
ELEVATION AB 2 / 4 FLAMES IN.
INTRLOCKED WITH ( ALL BURNER IN AB ELEVATION
BURNER IN THAT ELEVATION
ARE I/S.)
(2) VOTING IN BC ELEVATION WILL BE AVAILABLEMILL B FEEDER OR MILL C FEEDER I/S.
AND
ELEVATION B 2 / 4 FLAMES IN.
SATISFACTORY S/D OR 3 / 4 OIL
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 OIL BURNER ARE NOT FIRING.
OR
(3) OIL GUN IN THAT ELEVATION NOT SATISFACTORLY SHUTDOWN INTROLOCKED WITH 3 /
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4 OIL BURNER IN THAT ELEVATION NOT FIRING.
Scanners
MASTER FUEL TRIP (MFT)
• MFT or Boiler Trip means:
 Complete isolation of all fuel to furnace under certain conditions
• 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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Unit Logic
MFT consequences
 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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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
MFT
RELAY
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
Manual Emergency PB trip
Air flow less than 30% and boiler load not greater than 30%
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Reheater Protection
Reheater Protection Arming
THANK YOU …
QUESTIONS ?
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