This document provides an overview of the Furnace Safeguard Supervisory System (FSSS) implemented at the Butibori power project in India. It describes the hardware configuration using three systems: a Safety Manager system, DCS system, and MFT cabinet. It then summarizes the major functions and logics of the FSSS, including common control logics, fuel oil control logics, coal-fired control logics, and conditions for satisfactory boiler start up and shutdown. It also briefly discusses the run back function to reduce boiler load in the event of failures.

1. Furnace Safeguard & Supervisory
System
8 July 2020 VIPL
Avadhesh Tiwari

2. Furnace Safeguard Supervisory System
2
 Satisfactory Boiler start up & Shutdown
 Start up of individual oil system AB,BC,CD & EF
 Operation of fuel firing subject to certain conditions
A/B/C/D/E/F
 Protection and interlock of Oil /Coal System
8 July 2020 2

3. Hardware Configuration
FSSS is implemented using three different systems:
1. Safety Manager system
2. DCS System
3. MFT cabinet
In Butibori power project, totally three controllers (1S1, 1B6, 1B7 as the controller
name), 10 DCS cabinets are used for FSSS, list as below:
1. FSSS SYSTEM OVERVIEW

4. PHYSICAL REPRESENTATION OF PANEL

5. PANEL VIEW

6. The major functions implemented in 1S1
controller include
1. MFT/OFT processing
2. Furnace purge
3. Fuel oil leak test
4. Fuel oil burner control
These functions are all critical for safe boiler operation,
so the Safety Manager is used for 1S1 controller.
SAFETY MANAGER(1S1)

7. 1B61, 1B62 cabinet linked with 1B6 controller & C300
IOTA cards.
1B71, 1B72 cabinet linked with 1B7 controller & C300
IOTA cards.
1BJ61 Relay cabinet for 1B6
1BJ71 Relay cabinet for 1B7
1B6 controller implements the PULVERISER A/C/E system
start/stop control.
1B7 controller implements the PULVERISER B/D/F system
start/stop control.
DCS SYSTEM(1B6/1B7)

8. A. Common control logic
B. Fuel oil control logics
C. Coal-fired control logics
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FSSS logics can be broadly divided into 3
sections.

9. A. Common Control Logics
(a) Boiler purge logic
(b) Master fuel trip logic/Oil fuel trip
(c) Fuel oil leak test
(d) Scanner air Fans logic
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10. (a) Boiler purge Logic
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 %)
 Initiate a MANDATORY purge time cycle (5 min)
Consequence:
 Master Fuel Trip Relays are reset
 Firing of fuel into the furnace is allowed
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11. Furnace purge conditions
 MFT ACTION
 ANY ID FAN RUNNING
 ANY FDF RUNNING
 ANY APH RUNNING
 BOTH PA FAN STOPPED
 ALL PULV STOPPED
 ALL COAL FEEDER STOPPED
 ALL PULV OUTLET DAMPER CLOSED
 ALL OIL/PURG/ATOM/VALVE CLOSED
 NO FLAME DETECTED
 NO MFT CONDITION
 AIR FLOW >30%,DRUM LEVEL SUITABLE & FURNACE PRESSURE
SHOULD BE ADEQUATE
 HFO AND LDO LEAK TEST OK OR BYPASS
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13. (b) Master fuel trip logic
This ensures a safe shut down of the boiler in case of
any abnormal conditions in boiler.
MFT consequences
 Activate MFT trip relay
 Trips all mills
 Trips all feeders
 Trips PA fans
 Closes HFO trip valve
 Closes all elevation nozzle valves
 Close all pulveriser outlet dampers
 Closes all SH & RH spray MOVs
 Send the hardwired signal to DCS,ETS,Bypass and soot blowing system
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14. 14
 TURBINE TRIP AND LOAD >60%
 ALL FD FAN STOPPED
 ALL ID FAN STOPPED
 All PA FAN STOP WHILE ANY MILL IN SERVICE BUT NOT ANY GUN
 ALL SCANNER COOLING AIR FAN STOP & HEADER PRESS LOW
 SCANNER AIR FAN OUTLET HEADER PRESSURE LOW LOW (2/3 LOGIC)
 FURNACE PRESSURE HH TRIP(2/3 LOGIC)
 FURNACE PRESSURE LOW TRIP(2/3 LOGIC)
 DRUM LEVEL HH TRIP(2/3 LOGIC)
 DRUM LEVEL LOW LOW TRIP(2/3 LOGIC)
 ALL APH STOPPED
 TOTAL AIR FLOW <30%
 OPERATOR MANUAL TRIP
 REHEATER LOST PROTECTION
 LOSS OF ALL FUEL
 IGNITION DELAY
 LOSS OF ALL FLAME
The various abnormal operating conditions under which
Master Fuel Trip occurs are as follows:-

15. Conditions for MFT:
 Furnace pressure very high.
Tripping at : +20 mbar
 Furnace pressure very low.
Tripping at : -20 mbar
 Drum level very high.
Tripping at : +400 mm
 Drum level very Low.
Tripping at : -280 mm

16. Both FD fan tripped.

17. Both ID fan tripped.

18. Both APH tripped.

19. Secondary air flow very low

20. Turbine tripped & Load > 60%. (i.e. 180MW)

21. Both scanner cooling air fan tripped

22. Scanner cooling air fan pressure very low.
Tripping at : < 32.5 mbar

23. Loss of all flame trip:
Any one coal feeder running
And
All coal layers no flame
And
BC all corners no flame
And
AB all corners no flame
And
CD all corners no flame
And
EF all corners no flame.

24. Loss of all Fuel trip:
All LDO layer oil valve closed.
And
All coal feeder stopped.
Ignition delay trip:
After MFT reset no any gun taken in service
within 60 mins.
OR
After MFT reset, any BC gun not proven in
consecutives 3 attempt.

25. Both PA fan tripped
And
All mills not stopped
And
Any OIL corner is not running

26. Reheater protection trip:
 Total Fuel flow > 40Ton with any of the following
conditions.
1. Turbine’s all TV or GV closed & HP
bypass closed.
OR
2. Turbine’s all IV or RSV closed & LP
bypass closed.

27. Operator manual trip-
If operator wants stop boiler for maintenance
or for some other reason, he can do that by
pressing two MFT push buttons together.

28. Oil fuel trip (OFT)
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 Oil fuel trip logic(OFT) inspects the fuel oil
parameters. On any dangerous situations
which will keep boiler from safe operation
occures, OFT will fast cutoff the running oil
burners and close the oil supply shutoff valve.
 FSSS continuously supervise the OFT
conditions and will trigger the OFT if any
conditions occures

29. LDO OFT CONDITIONS
 Manual trip. Operator close command to the
LDO supply shut off valve.
 MFT
 Ldo shut-off valve not opened pulse
 Ldo supply line pressure LL with 5sec and
any burner oil valve is opened
 Ldo atomosing pressure LL with 5sec and any
burner oil valve is opened
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30. LDO OFT WILL BE RESET UNDER
FOLLOWING CONDITIONS
 No any LDO OFT condition exits
 LDO supply shut-off valve is closed
 All LDO burner oil valve closed
 LDO oil leak test complete
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31. HFO OFT CONDITIONS
 Manual trip. Operator close command to the
HFO supply shut off valve.
 MFT
 HFO shut-off valve not opened pulse
 HFO supply line pressure LL with 5sec and
any burner oil valve is opened
 HFO atomosing pressure LL with 5sec and
any burner oil valve is opened
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32. HFO OFT WILL BE RESET UNDER
FOLLOWING CONDITIONS
 No any HFO OFT condition exits
 HFO supply shut-off valve is closed
 All HFO burner oil valve closed
 HFO oil leak test complete
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33. LDO ignition conditions
 MFT RESET
 LDO OFT reset
 LDO supply shut-off valve opened
 Flame detector fan cooling air pressure normal
 Atomizing air pressure normal
 Boiler drum level normal or RB action
 Furnace pressure normal or RB action
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34. HFO ignition conditions
 MFT RESET
 HFO OFT reset
 HFO supply shut-off valve opened
 Flame detector fan cooling air pressure normal
 Atomizing steam pressure normal
 Boiler drum level normal
 Furnace pressure normal
 HFO supply oil temperature normal
 LDO BC layer running or any coal layer running
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35. (d) Scanner air fan logic
1.SAF start permissive-
(i) SAF-A in remote & no any local fault.
2. Auto start condition-
(i) The cooling air fan B protection trip
(ii)Any of flame detector air header pressure low
3. Stop permissive-
(i) The cooling air fan B running and fan A in
remote
(ii)MFT occurs and fan A in remote
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36. Coal fired control logics-
 All six layers mill system sequence control
 Single device interlock control like coal
feeder,pulverizer & relevant dampers
 Coal fired control logic accomplishes the mill
system start/stop control,supervision of every
running coal layer parameters and fast cut off
of coal if necessary to ensure the furnace in
safety condition.
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37. Coal ignition conditions
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 MFT is reset
 The DP of furnace and secondary air wind-
box is normal
 The DP of furnace and hot primary air header
not low
 Hot secondary air temperature >160 deg
 Any primary air fan running
 Swaying burner tilt position horizontal or any
coal layer in service

38. Coal layers ignition energy requirements
Any of the following conditions satisfied means Coal
layer A ignition energy sufficient
 AB oil layer in service
 Coal layer B federate >50% under boiler load >30%
 Any two coal layers in service under boiler load >60%
Any of the following conditions satisfied means Coal
layer B ignition energy sufficient
 AB oil layer in service
 BC oil layer in service
 Coal layer A federate >50% under boiler load >30%
 Any two coal layer in service under boiler load>60%
38

39. Coal layers ignition energy requirements
Any of the following conditions satisfied means
Coal layer C ignition energy sufficient
 BC oil layer in service
 CD oil layer in service
 Coal layer B federate >50% under boiler load
>30%
 Coal layer D federate >50% under boiler load
>30%
 Any two coal layers in service under boiler
load >60% 39

40. Coal layers ignition energy requirements
Any of the following conditions satisfied means
Coal layer D ignition energy sufficient
 CD oil layer in service
 Coal layer C federate >50% under boiler load >30%
 Coal layer E federate >50% under boiler load >30%
 Any two coal layer in service under boiler load>60%
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41. Coal layers ignition energy requirements
Any of the following conditions satisfied means
Coal layer E ignition energy sufficient
 EF oil layer in service
 Coal layer D federate >50% under boiler load >30%
 Coal layer F federate >50% under boiler load >30%
 Any two coal layer in service under boiler load>60%
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42. Coal layers ignition energy requirements
Any of the following conditions satisfied means
Coal layer F ignition energy sufficient
 EF oil layer in service
 Coal layer E federate >50% under boiler load >30%
 Any two coal layer in service under boiler load>60%
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43. Coal feeder A
The following conditions are the permissive
conditions for feeder start up:-
 Pulverizer A is running
 Coal layer ignition condition exits
 Coal layer A ignition energy satisfied
 Coal feeder A sealing air damper is opened
 Coal feeder A outlet vavle opened
 Coal feeder A feedrate is minimum
 Pulverizer A outlet temp ok(b/w 65 to 82deg)
 Coal feeder A in remote control
 No any coal layer trip conditions exits
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44. Coal feeder A auto stop under following
conditions-
 Pulverizer A stopped under coal feeder A
running
 Any pulverizer A trip condition
 Coal feeder A outlet vavle closed with 5sec
delay
 Coal feeder A outlet blokage with 20sec delay
 Coal feeder A belt zero coal with 5sec delay
 Coal feeder A inner over temperature with
3sec delay
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45. Thank You

46.  Run Back (RB) is a function initiated by CCS system when the
boiler could not operate with the set load due to the failure of
major auxiliary device of the boiler such as water feed pump,
forced/induced air fan, primary air fan, etc. in case the unit
load is above 50%.
 The purpose of RB function is to reduce the input fuel fast and
keep the boiler in safe operating condition.
 FSSS system will perform the RB action only when more than
three coal layers are in service; the logic will remove the
upper coal layers in service from top to bottom preferentially
in proper time interval to match the boiler load and the boiler
auxiliary device’s contribution.
Run Back

47. Actions after RB:
When more than three coal layers are in service, if FSSS received the RB
command, the following will be performed:
 Fast start the LDO BC oil layer with pair mode.
 Override close the return LDO shut off valve.
 Remove coal layer F, E and D from top to bottom layer. Coal layer F will
be shutdown first. Coal layer E will be shutdown if still more than three
coal layers are in service at the moment 2 seconds adjustable after coal
layer F shutdown.
 The process will continue in that way until coal layer D is shutdown.
RB Reset Condition:
The following conditions will reset the RB signal (or):
 Operate cancels the RB function.
 The RB succeeded with the unit load less than the predefined RB target.