The document summarizes the key components and functions of a fuel firing system and burner management system for a boiler. It describes the operational functions included like furnace purge supervision, flame monitoring, and burner protection. It explains the boiler purging process and purge permissives that must be satisfied. It also outlines the start-up sequences for oil elevations in pair mode and elevation mode. Additional details provided include secondary air damper control, mill panel functions, field equipment, and mill start permissives.

1. Fuel firing system
& Burner Management
System
Manzoor Alam
(Operations)

2. INTRODUCTION
Generally, furnace oil or any kind of fuel is susceptible to explosions hazards. It has been
established that the majority of explosions occur during the start up , shut down and low load
operations
 For high capacity boilers where the fuel input rate is also high, major furnace explosions can
result from the ignition of un burnt fuel accumulated in the first 1 to 2 seconds.
Furnace Safeguard Supervisory System (FSSS) is designed to ensure the execution of a safe,
orderly operating sequence in the start up and shutdown of fuel firing equipment and to prevent
errors of omission and commission in following such a safe operating procedure

3. Operational functions included in FSSS
• Furnace purge supervision
• SADC modulation and on/off control and supervision in corner fired
boilers.
• Igniter on off control and supervision.
• LDO/HFO on off control and supervision.
• Flame Monitoring & Overall flame failure protection.
• Post purge trip of BOTH ID & FD.
• Damper control of BOTH ID ,FD & PA FANS.
• Boiler protection.

5. BOILER PURGING
• Boiler purging is a cleaning processes of boiler, with the help of purging
we remove all unburnt particles or fuel from flue gas path.
• Boiler purging is done for 9 minutes (540 sec) .
• Before boiler startup or after every boiler tripping ,purging process is
to be performed.
• The “purge ready” condition is established when all of the
• following permissives are satisfied:

7. Purge permissive
1. No boiler trip command exists.
2. All FSSS “system power” available, as follows :
a) Battery power is available. (220V DC)
b) Unit interrogation power is available. (24V DC)
c) Unit drive power is available. (220 vdc from field)
d) Each individual oil elevation power is available (elev AB, CD, EF & GH).
e) Each individual coal elevation power is available (elev A, B, C, D, E, F,G,H).
3. Unit air flow is greater than 30%.
4. Nozzle tilts horizontal and air flow less than 40%.
5. Both primary air fans are off.

8. 6. The following conditions exist at the oil firing equipment:
a) The Light Oil Trip Valve is closed.
b) The Light Oil (nozzle) Valves are closed on AB elevation.
c) The Heavy Oil Trip Valves and Heavy Oil Recirculation Valve are closed.
d )The Heavy Oil (nozzle) Valves are closed on all elevations ( AB,CD, EF & GH).
7. The following conditions exist at the coal firing equipment:
a) All pulverizers are off.
b) All feeders are off.
c) All pulverizer hot air gates are closed.
8. All flame scanners on all scanner elevations indicate no flame.
9. The auxiliary air dampers at all elevations are modulating (not closed).
10. All separated overfire air (SOFA) dampers are closed.
11. Scanner Air fan on and scanner air to furnace dp > 152 mmwc

9. • When all these conditions are satisfied, the purge sequence may be initiated
by the Operator.
• If any of the “purge ready” permissives are lost during the purge sequence,
the “purge ready” condition is removed and the purge timer (Purge Time is
9 minutes approx.) is reset.
• When the purge sequence is completed, the “Master Fuel Trip” memory is
reset. A “No Master Fuel Trip” condition is now established and the “CAUSE
OF TRIP” memories are reset.
• The Operator may now place the firing equipment in service.

10. ARRANGEMENT OF THE SYSTEM
The system consist of following major parts.
Logic cabinet.
Console insert.
Secondary air damper control panel
Mill panel
Field equipments

11. Logic cabinet and Console insert
• Logic cabinet and Relays –It is the heart of the system which includes all the
logic hardware. The Cabinet includes the control relays,latch relays ,time delay
relays and program timers.
• Console insert-It contains all command devices( push buttons)like switches for
initiating controls and all the feedback devices( indicating lamps) require to
monitor the status of the fuel firing equipment and their auxilliaries. The console
insert connected to the logic cabinet through cables.

12. SECONDARY AIR DAMPER PANEL
It regulates air adjacent to the fuel compartment are termed as Auxiliary or
Secondary dampers.
Auxiliary air dampers are adjust to maintain the fixed differential pressure
between wind box & furnace.
SADC in all elevation & corners are grouped control in proportion to wind box
furnace differential pressure.
All these command signals are generated in the logic cabinet and are transmitted
to the SADC panel

13. MILL PANEL
The flow or lack of flow of coal to the mills is to be monitored so as to give
an alarm when there is no coal flowing to the mill and also when there are
other interlocks
When the coal is pulverized in the mill, depending on the quantity of coal
being grounded the mill may either be overloaded or it may be running at
no load conditions
High current relay and Low current relay

14. FIELD EQUIPMENTS
Nozzle valves
Igniter advance/retract mechanism
Mill discharge gate
Hot air gate
Secondary air damper control
Ignitor cabinet
Flame scanner assembly
Local gun maintenance switch box

15. FLAME MONITORING
TOTAL NO. OF SCANNER IN BOILER IS 32.
COAL FLAME SCANNER NO. 16 .
LDO/HFO FLAME SCANNER NO. 16.
TWO FAN (ONE IS RUNNING ANOTHER IS
STANDBY)PRESENT FOR COOLING THE FLAME
SCANNER .(AC +DC)
COOLING AIR HEADER PRESSURE IS >152 mmWC

17. LDO ELEVATION START PERMISSION
CONDITIONS- to open all oil nozzle valve
1. No master fuel trip signal exists.
2. LOTV should be open. (supply pr. > 18.5 ksc)
3. LDO HDR pressure normal (Pressure > 7 ksc )
4. Atomizing air pressure normal. (pressure > 3.5 ksc)
5. Nozzle tilt horizontal and total air flow <40%(his will be bypassed
after any feeder is proven).

18. • The Oil Header Trip Valve is automatically closed if any of the following
conditions exist.
1. The Oil Trip Valve is proven “not closed”, if any oil (nozzle) valve is “not
closed” and either the following conditions exist, for more than two seconds.
a. The oil header pressure is “low”.
b. Atomizing header pressure is “low”.
2. A “master fuel trip” signal (either Hardwired or Soft signal) is established.
3. Oil Trip Valve “Failed to Open” signal is established

19. Oil Elevations Start-Up

20. • Pair mode operation is selected automatically when any one
of the following conditions exists.
1) All coal elevations are not in service
2) Both coal Elevations A & B are not in service AND Elevation AB Back
up trip exists.
Initially, let us assume that pair 1 and 3 is to be placed in service. Pressing
“PAIR 1-3
START Push Button” for the elevation being started, will cause the
following events :
When the Push Button is released, the 70 second counting period is
started and
corner-1 receives a “start” command instantaneously and corner-3
receives a
“start” command after 15 seconds.
Pair Mode Operation
(Elevation AB, typical for elevations CD, EF, GH)

21. After the “start” command is established for corner-1, the corner oil gun will be
placed in service if all the following conditions at corner-1 are satisfied.
1)The associated corner scavenge nozzle valve is closed.
2)The associated corner manual atomising steam isolation valve is open.
3)The local maintenance switch in the associated corner is placed in the
“REMOTE” position.
When “start” command is established at corner-1, the HEA igniter gets advance
command provided all the following conditions are satisfied.
1) LO Nozzle valves and HO Nozzle valves are closed.
2) Discriminating flame scanner shows no flame.
When the spark rod of HEA ignitor is fully advanced, the HEA Rod “ADVANCED”
light comes on.

22. Atomising valve gets open command if corner trip is not present. Once the
atomising valve is fully opened, oil nozzle valve gets open command and the
exciter of HEA ignitor is energized when oil nozzle valve has moved from closed
position.
When the corner oil nozzle valve (LO/HO) is in “not closed” condition, then a 15
seconds trial time for the HEA ignitor is initiated. When the corner oil nozzle
valve (LO/HO) is proven open, the oil nozzle valve “OPEN” light comes on. At the
end of the 15 seconds ignitor trial time, HEA exciter is de-energised and HEA
ignitor is retracted. HEA exciter will be de-energised and HEA ignitor will be
retracted, 2 seconds after the Oil Nozzle Valve is open and the Discriminating
Scanner Shows Flame

23. If the associated corner discriminating scanner indicates flame the
“DISCRIMINATING SCANNER FLAME” light comes on. Corner-1 oil gun (LO/HO) is
now in service.
When the 15 seconds counting period expires, corner-3 oil gun start command is
established and will be placed in service in the same manner as previously
described for corner-1.
When the seventy second counting period expires (for corner 1 & 3), the fifteen
second timer for corner 3 is reset and oil gun in Corner-1 & 3 will be shut down if
the associated oil nozzle valve is not fully open.
Same for pair 2 & 4 corners.
When at least three of the four oil (LO/HO) Nozzle valves are fully open, the oil
elevation (LO/HO) is in service. The “IGNITION PERMIT” is established for the mill
associated with the oil elevation. The “Ignition permit” is now satisfied and the
associated mill can be placed in service after other permissives are satisfied.

24. Elevation Mode Operation (Elevation AB, typical for elevations CD, EF, GH)
Elevation mode operation is automatically selected when either of the adjacent coal
elevations associated with (LO/HO) oil elevation is in service.
When the above condition exists, the “Elevation Mode Operation” is automatically
selected and the associated (LO/HO) oil elevation is placed in service in the following
manner (provided the “oil elevation start permit” remains satisfied).
When pair 1-3 start or pair 2-4 start PUSH BUTTON is pressed, an “Elevation Start”
command is established for corner 1 & 3. After the “Elevation Start” command is
established, a forty second counting period is started to establish an “Elevation Start”
command for corners 2 & 4. Corners 1 & 3 are now placed in service as previously
described in the “Pair Mode Operation” section. When the forty second counting period
expires, corners 2 & 4 are placed in service as previously described in “Pair Mode
Operation” section.
When atleast three of the four (LO/HO) nozzle valves are fully open , the (LO/HO)
elevation is “proven in service”.

25. LDO GUN SYSTEM
BOILER
LDO GUN
IGNITOR
ATOM. AIR LINE
LDO OIL LINE
ATOMIZING V/V
PURGE V/V
OIL V/V
start stop
After 5
sec. of
purging

26. SECONDARY AIR DAMPER CONTROL
AUXILIARY AIR DAMPER CONTROL
All elevations of the aux. air dampers will be automatically switched to “Manual”
control and then commanded to open 100%, if any one of the following
conditions exist.
• All FD fans are off
• All ID fans are off
• Master fuel trip exists
When the auxiliary air control is placed in the “Auto” mode of operation , the
auxiliary air dampers modulate to control wind box to furnace differential
pressure at a predetermined set point.
During the furnace purge cycle, all auxiliary air dampers modulate to maintain
wind box to furnace differential pressure at a predetermined set point.

27. When the unit load exceeds 30% of MCR, the following events occurs :
The wind box to furnace differential set point is gradually increased as the unit load is
increased. Conversely, the differential pressure set point is gradually decreased as unit
load is decreased. The rate of increase (or decrease) is controlled by the auxiliary
damper controller.
When the Unit Load is increased above 30% MCR, the Auxiliary air dampers on
elevation AB, BC, CD, DE, EF FG,GH & HH are closed in a timed sequence (10 seconds
interval) provided the associated coal elevations are not in service and the associated
oil elevations are not in service. The auxiliary air dampers are closed, starting from the
top elevation, progressing towards the lowest elevation.

28. When the unit load is reduced below 30% of MCR, the following events occur
• The wind-box to furnace differential pressure set point reverts to its original
value.
• The auxiliary air dampers associated with the coal and LO/HO elevations not
in service are opened in a timed sequence (10 sec. interval) starting at the
lowest elevation, progressing towards the top.
When a LO/HO Elevation is started (i.e. when the associated “elevation back-
up” trip is removed) the associated auxiliary air dampers in that elevation are
set to preset position for LO/HO firing.
When the “Post Trip Purge Time Expired” command is established and all FD /
ID fans are not off and a Master fuel trip” command doesn’t exist, then a 30
seconds counting period is started. After it expires, the “Open All Auxiliary Air
Dampers” command is removed from memory.

29. FUEL (COAL) AIR DAMPERS CONTROL
All fuel air dampers of all elevations are signaled to “open” when any of the following
events occur :
1. Both Forced Draft fans are off OR Both Induced Draft fans are off.
2. Master Fuel Trip occurs.
When the “master fuel trip” signal exists, the furnace purge cycle can be started. When
the selected purge permissives are satisfied, the five-minute “post trip” purge time is
started.
When this time expires and at least one Forced Draft fan is on and at least one Induced
Draft fan is on, the fuel air dampers’ “open” command is removed.
When the feeder is “proven” (feeder on for more than 50 seconds), the feeder speed is
released to “auto” control. The fuel air dampers modulate as a function of the
associated feeder speed.
When a feeder is not proven for more than fifty (50) seconds the associated elevation
of fuel air dampers are closed.

31. MILL START PERMISSIVES
DESCRIPTION SET POINT
1)PULV START PERMIT:
[ANY OIL ELEVATION IN SERVICE OR ANY FEEDER PROVEN OR
(NOZZLE TILT HORIZONTAL AND AIR FLOW < 40 %)] AND NO MFT.
2)START PERMIT FROM PLOS:
Lube oil temperature is adequate ( > 30 °C) AND
Lube oil Pump ‘’ON’’ for more than 15 minutes AND
Lube oil pressure at cooler outlet is NOT LOW (> 0.8 bar).AND
Lube oil filter not dirty (DP < 2.0 bar) AND
Lube oil flow to the gearbox is NOT LOW (FLOW > 200 LPM)AND
All bearing temp of Gearbox is within ALARM limits(<75 °C).

32. 3)PULVA DISCHARGE VALVES OPEN
4)PULV A O/L TEMP N.HIGH < 77° C
5) CAG A OPENED
6) NO AUTO UNSUCCESSFUL START
7) PA PERMIT AVAILABLE: [HOT PA TO FURNACE DP > 540
MMWC] AND[(ONE PAF RUNNINGAND< 4 PULVERIZERS
ON)OR(BOTH PA RUNNING)]
8) BUNKER O/L GATE OPEN
9) FEEDER I/L GATE OPEN
10) FEEDER A IN REMOTE
11) BURNER MANUAL ISO. GATES OPEN
12) NO PULVERISER TRIP
13) PULV. OFF

33. 15) IGNITION PERMIT AVAILABLE-
PULV. A: MINIMUM 3 0F 4 ELEV. AB OIL GUNS PROVEN
OR.BOILER LOAD >30% MCR
AND. FEEDER-B PROVEN GREATER THAN 50% LOADING.
(42TPH)
16) SA BOWL DP HIGH (Any) > 203 MMWC
17) MILL INERTING VALVE CLOSED

34. 1) MFT
1) TRIP FROM PLOS
a. Both lube oil pumps not ON 10 sec Delay
b. Lube oil pump ON FOR 60 SEC and lube oil
pressure after cooler < 0.5 bar (delay 15 s)
c. Lube oil temperature after cooler is >65 ° C
d. Lube oil flow to the gearbox < 175 LPM).
e. Lube oil level V.low
3)ANY PULV. DISCHARGE VALVE N.OPEN
4)IGNITION ENERGY NOT AVAIALBLE AND
SUPPORT IGNITION REQRD.
5) MOTOR BEARING TEMP V.HIGH >95 ° C
OR MILL NDE /DE I/P SFT BRG TEMP >85° C
OR MILL THRUST BEARING TEMP >85° C
OR MTR WNDG TEMP >120 ° C (2OUT OF 6)
Delay 2 sec
Delay 2 sec
Delay 2 sec
Delay 2 sec
MILL TRIP CONDITION

35. 6) SEAL AIR HDR/PULV BOWL DP LOW .AND.
PULV. A ON (Any)
<102 mmWC
WITH 10 SEC
DELAY
7) LOSS OF PRIMARY AIR :
BOTH PA FAN OFF AND ANY MILL RUNNING
OR HOT PA TO FURN DP LOW
< 540
MMWC(10 S
DELAY)/<476
MMWC(5 SEC
DELAY)
8) PULV. FAIL TO START >10 SEC.

36. Mill Ignition permissive for A ( H)
a. Elevation “AB” oil is proven in service (light oil or heavy oil) [three
out of four oil valves are open and firing rate is adequate (i.e. Oil
Header Pressure adequate and Discriminating Scanners Show flame)].
OR
b. Feeder “B” is proven (feeder is on for at least fifty seconds) and its
feeder speed is greater than 50% and boiler load is greater than 30%
MCR.
(For Mill H , oil elevation GH used, and feeder G must be proven,
loading of G >50%)

37. Mill ignition permissive for B (C,D,E,F,G)
a. Elevation “AB” oil is proven in service (light oil or heavy oil) [three out of
four oil valves are open and firing rate is adequate (i.e. Oil Header
Pressure adequate and Discriminating Scanners Show flame)].
OR
b. Feeder “A” is proven (feeder is on for at least fifty seconds) and its feeder
speed is greater than 50% or Feeder “C” is proven (feeder is on for at
least fifty seconds) and its feeder speed is greater than 50% and boiler
load is greater than 30% MCR.
OR
c. Feeder “C” is proven (feeder is on for at least fifty seconds) and its feeder
speed is greater than 50% and Elevation “CD” oil is proven in service
[three out of four oil valves are open and firing rate is adequate (i.e. Oil
Header Pressure adequate and Discriminating Scanners Show flame)]

38. MASTER FUEL TRIP
An abnormal unit shutdown occurs when a “master fuel trip” signal is
established. A “master fuel trip” signal is established when there is a
boiler trip condition present after the furnace purge cycle has been
completed.
Boiler master fuel trip is basically a part of Boiler Management System. It
is actually the control circuit to send trip commands to boiler systems and
critical drives upon the occurrence of unsafe operating conditions

39. MFT Trip conditions
There are the conditions which may cause an MFT to occur.
When any unsafe condition arises, the field instruments sends
the signal to ACN CS Panel.
The signal is processed in this controllers & generates the Digital
Output signal.
This DO operates the MFT relay which in turn sends trip
commands to critical devices
TRIP TO CRTICAL DRIVES
SIGNAL
FROM FIELD
ACN CS
CONTROLLER
SIGNAL TO
ACN CS
DO OPERATE
MFT RELAY

40. MFT CONTROLLER- ACN CS
WE HAVE TRIPLE REDUNDENCY MFT CIRCUIT, 3 nos of ACN CS CONTROLLER

42. Condition For Boiler MFT
1. Loss of any (unit) critical power.
2. Loss of DCS control capability for more than ten seconds. (ID,FD,FW ACN Controller fail)
3. Both ID (Induced Draft) fans are off.
4. Both FD (Forced Draft) fans are off.
5. Unit airflow is less than 30 % BMCR.
6. All feed water pumps are off for more than twenty seconds and loss of fuel trip arming.
7. Furnace pressure is at the “high trip” setpoint.
8. Furnace pressure is at the “low trip” setpoint.
9. Loss of Reheat Protection.
10. Both “EMERGENCY TRIP” (hard) push buttons are pressed simultaneously or the
“MFT” (soft) push button is activated.
11. Economizer inlet feed water flow low for more than 15 seconds and loss of fuel trip arming.
12. Evaporator tube metal temperature high for more than three seconds.
13. Separator level high.
14. Separator Pressure high.
15. MFT Relay Tripped.
16. Loss of fuel trip.
17)All FSSS processor failed (ACN Controller fail)
18)Both network failed(2/3 dual ethernet network between MFT ACN controller & DCS FAIL TO COMMUNICATE)

43. Loss of any critical power
• Unit drive power = 220vdc
• Instrument and system power = 24 vdc

45. Fan Stopped Concept
HT SWGR
11 KV
ID/FD fan A
HT SWGR
11KV
ID/FD fan B
DI
DI
DI
DI
DI
DI
INTERFACING
&
PROCESSING
2/3 LOGIC IN
DCS
ACN CS
Panel
D01
D02
D03
CFJ01
CFJ02
CFJ04
MFT Relay
Panel
Signal
to trip the
critical
devices
BOTH FD FAN TRIP Hard wire logic OPEN SCANNER EMERGENCY DAMPER

46. Air flow low
• Trip value AIR FLOW < 30 % ( 695 tph )
• Air flow measurement:
Total secondary air flow = right side secondary air + left side secondary air
Total Primary air flow = All Mill PA ( A to mill H)
Total air flow = Total secondary air + Total Primary air ( MFT on < 695 )
Total air flow % = (Total secondary air + Total Primary air) *100
BMCR flow (2513)
Air flow low 2 out of 3 and internal derived protection of boiler

47. Separator level very high
• Separator level high trip at 11.56 Mtr
• Separator level measurement :
Separator 1 level = Two level transmitters
Separator 2 level = Two level transmitters
Separator level trip value = Avg of (pressure compensated lvl1 & lvl2)

48. Spiral Wall temp. Very High
• Out of 72 temp elements if any 4 reaches value >=477° C, time delay
of 3 sec.

49. Separator pressure very high
• Separator pressure high trip on 290 Ksc
• Separator pressure trip is 2 out of three protection , protection is generated by median through
4 pressure transmitter
• Median is generated by internal derived logic to minimize error and fault
• Measurement : Two no's of PR TX is given in each sep 1 and 2

50. ECO inlet flow very low
• Eco inlet flow trip < 705 TPH with delay of 15 sec
• Eco inlet flow is 2 out of 3 protection provided for boiler to insure minimum required flow for
safety of boiler . Trip is generated by compensated eco inlet flow .
• Measurement : Three nos of flow Tx at eco inlet
Two nos of temp Tx at eco inlet ( for temp compensation)

51. All feed water pump off
MFT

52. Furnace pressure

54. Unit flame failure

55. Unit flame failure
Elevation AB no flame vote
Elevation BC no flame vote
Elevation CD no flame vote
Elevation DE no flame vote
Elevation EF no flame vote
Elevation FG no flame vote 2 sec delay
Elevation GH no flame vote
Elevation HH no flame vote
Any feeder proven
Unit
Flame
Failure

56. Elevation flame voting
• AB ELEVTAION NO FLAME VOTING LOGIC :
AB NO FLAME
VOTE

57. Elevation flame voting
• BC ELEVTAION NO FLAME VOTING LOGIC :
BC NO
FLAME
VOTE

58. LOSS OF ALL FUEL
• Loss of fuel trip

59. POST PURGE ID & FD TRIP
MEDIAN OUTPUT FURNACE PR
WHEN PURGING IS COMPLETED & BEFORE LIGHTUP THE BOILER FURNANCE
PRESSURE HIGH(+152 mmWC) OR LOW LOW (-228 mmWC) IS COMING ALL ID
& ALL FD IS TRIPPED TO PROTECT THE BOILER.
HIGH & LOW SIGNAL IS COMING TRANSMITTER FROM MFT LOGICS.

60. Less than fireball and loss of AC
220 VDC : HOTV,LOTV,HORV
240 VAC : ALL LONV, HONV, HEA IGNITER, MDV,HAG,CAG,FEEDER O/L GATE
24 VDC : DCS POWER, FIELD INSTRUMENTS, TRANSMITTERS, SWITCHES

61. AFTER MFT WHAT???...
When a “master Fuel trip” signal is established, the following events will occur
1. The Light and Heavy Oil Trip Valves are closed.
2. All corner oil valves are closed.
3. All pulverizers and feeders are shut down.
4. All pulverizer hot air gates are closed.
5. All pulverizer hot and cold air dampers are closed.
6. The primary air fans are tripped.
7. The fuel and auxiliary air dampers are opened and the auxiliary air dampers
control is transferred to “manual”.
8)Trip Turbine
9)Trip soot blower system and ESP
10)Force Close superheater & reheater Spray mov,cv.

62. The main phenomena after the MFT
activated:
• The alarm signal of the “the MFT activated” is sent out.
• All boiler fuel are cut off.
• No fire is detected by the fire scanner, and no fire can be
watched in flame monitoring TV;
• The Main Steam and Reheater Steam temperature drops
sharply. If the MFT activation, results from the tripping of
the Turbine or the Generator, the steam pressure will rise
quickly and may cause the safety valve act.
• The furnace pressure falls greatly.

63. MAJOR CAUSES FOR EXPLOSION IN A
BOILER
 IMPROPER PURGING OF THE FURNACE, GAS & AIR PATH
 INADEQUATE & IMPROPER IGNITION
 MAINTAINING FUEL SUPPLY FOR LONG PERIOD WITHOUT
ESTABLISHING COMBUSTION
 RELIGHTING FUEL SOON AFTER FLAME OUT WITHOUT ROPER
PURGING
 MAIN FUEL INTRODUCTION WITHOUT ADEQUATE IGNITION
ENERGY.