ID/FD FAN LOGIC SYSTEM

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PURGE PERMISSIVESAll 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 closed19 January 2012

TO FSSS

Wind box to furnace DP is adequatePMI Revision 00

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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.19 January 2012 PMI Revision 00 3

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 Manual Emergency PB trip Air flow less than 30% and boiler load not greater than 30%19 January 2012 PMI Revision 00 4

MFT RELAY

1. ALL ID FANS OFF Arming: Logic: Always armed Both ID Fans OFF Contact sensed by MFT panels

Purpose:

Anticipatory protection to prevent furnace pressurization

Protection Delay: 0 sec INSTANT.

Loss of furnace pressure control and balanced draft

Protection Check:

Simulate the signals from ID Fans Electrical Control Circuit

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2. ALL FD FANS OFF Arming: Logic: Always armed Both FD Fans OFF Contact sensed by MFT panels Anticipatory protection to prevent reducing firing condition Loss of total air flow control and balanced draft

Purpose:

Protection Delay: 0 sec INSTANT.

Protection Check: Simulate the signals from FD Fans Electrical Switchgear

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3. LOSS OF ALL FUEL Arming: Logic: Any HFO/LFO nozzle valve NOT closed All LFO cut off AND All HFO cut off AND All Feeders OFF Initiation of a mandatory purge cycle to restore furnace

Purpose:Backup protection to trip remaining equipment (eg. PA Fans) 0 sec INSTANT.

Protection Check: Keep oil manual isolating valves in any one elevation any one corner (done by OPN), simulate status of manual valve (done by C&I), then give sequence start command to that corner Revision 00 19 January 2012 PMI

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4. FLAME FAILURE Arming: Logic: Any Feeder Proven for 2 sec

Protection Delay: 0 sec INSTANT.

All Elevations A to K voted NO Flame Eg. Elevation A voted no flame means (AA 3/4 fireball scanners sense no flame AND AB 3/4 fireball scanners sense no flame AND AB 2/4 oil guns not proven in service) OR Feeder A Not Proven for 2 sec Stop firing under unstable flame fireball conditions

Protection Check:

Simulate feeder proven status without any oil in servicePMI Revision 00 8

19 January 2012

5. FURNACE PRESSURE VERY HIGH Arming: Logic: Always armed 2 out of 3 pressure switches sense furnace pressure very high > +150 mmwc To stop fuel firing under explosive tendency of furnace 0 sec INSTANT.

Purpose:

Prevent furnace structural distortion Protection Delay: Protection Check:

Simulate from protection instrument, or by actual pressurization if agreed by Operation Head.19 January 2012 PMI Revision 00 9

6. FURNACE PRESSURE VERY LOW Arming: Logic: Always armed 2 out of 3 pressure switches sense furnace pressure very low < -175 mmwc To stop fuel firing under implosive tendency of furnace Prevent furnace structural distortion 0 sec INSTANT.

Purpose:

Protection Delay: Protection Check: Simulate from protection instrument, or by actual depressurization if agreed by Operation Head.

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7. DRUM LEVEL VERY HIGH Arming: Logic: Purpose:Always armed 2 out of 3 logic derived from hydrastep-left-1, hydrastepright-1 and drum level transmitter > 250 mm To prevent water carry over to superheater headers and subsequently to turbine 10 sec.

Protection Delay: Protection Check: Actual (increase feed water flow slowly until level reaches trip limit).

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8. DRUM LEVEL VERY LOW Arming: Logic: Always armed 2 out of 3 logic derived from hydrastep-left-2, hydrastepright-2 and drum level transmitter < -375 mm

Purpose:

To prevent waterwall tubes starvation To prevent BCW pumps starvation 5 sec.

Protection Delay:

Protection Check:

Actual (decrease feed water flow slowly until level reaches trip limit).

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9. ALL BFP OFF Arming: Logic: Always armed Both TDBFPs sensed Not Working AND MDBFP sensed OFF

Purpose: Anticipatory protection for Drum Level Very Low To prevent economizer tubes starvation

Protection Delay: Protection Check: 10 sec. Simulate OFF contact of all BFP from BFP control panel

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10. ALL SAH OFF Arming: Logic: Always armed Both Secondary Air Heaters: electric motor OFF AND air motor OFF Preventing poor furnace combustion due to low secondary air temperature Preventing flue gas damper isolation in all air heaters

Purpose:

Protection Delay: 5 sec.

Protection Check: Actual.19 January 2012 PMI Revision 00 14

11. WATERWALL CIRCULATION INCORRECT Arming: Boiler ON

Logic: All BCW OFF (OR) 2/3 running BCW DP < 0.68 ksc

Purpose: Preventing damage to waterwall tubes due to insufficient cooling flow/circulation

Preventing DNB (departure from nucleate boiling)

Protection Delay: 5 sec.

Protection Check: Equalizing DP transmitters to simulate DP low.

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12. TOTAL AIR FLOW < 30% Arming: Always armed

Logic: Total Air Flow (Primary Air + Secondary Air) < 30% of full load air flow (30% of 1800 Tph = 540 Tph)

Purpose: Ensuring absolute minimum required quantity of air flow even during startup Preventing localized accumulation of unburnt oil during startup

Protection Delay: 0 sec - INSTANT.

Protection Check: Actual.

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13. REHEATER PROTECTION Arming: Logic: HP bypass AND LP bypass charged for the first time > 2% Generator Circuit Breaker Open AND (HP bypass OR LP bypass Fail to Open) OR Reheater Inlet (HP) OR Outlet Path (IP/LP) Blocked Ensuring absolute minimum required quantity of air flow even during startup Preventing localized accumulation of unburnt oil during startup

Purpose:

10 sec. Protection Check: Actual.19 January 2012

Protection Delay:

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14. LOSS OF 24V DC Arming: Logic: Always armed If 24V supply to any 2 MFT panels is lost, it will initiate a hardwired MFT protection through 220V contactor circuit.

Purpose: If 24V fails, the processors cannot execute any logic, leading to unsafe condition

Protection Delay: 0 sec INSTANT.

Protection Check: By 24V breaker simulation in MFT panel.

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15. LOSS OF 220V DC Arming: Logic: Always armed If 220V supply to any 2 MFT panels is lost, it will initiate a soft MFT protection through processor logic.

Purpose: If 220V fails, backup protection for 24V failure will be unavailable.

Protection Delay: 2 sec.

Protection Check: By 220V breaker in MFT panel.

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17. 2/3 PROCESSORS FAIL/FROZEN Arming: Always armed

Logic:

If any 2 MFT processors out of 3 go into failed state, or if any 2 MFT processors go into frozen output state, it will initiate MFT protection. This ensures that at least 2 processors are in healthy condition at any point of time when boiler is in service. Failure of processors leads to unsafe condition 0 sec - INSTANT.

Purpose:

Protection Delay: Protection Check: By actually creating frozen output state in processors.

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17. 2/3 PROCESSORS COMMN FAIL Arming: Always armed

Logic:

If any 2 MFT processors out of 3 stop communicating with the Ethernet network (redundant net-A and net-B), they will initiate MFT protection This ensures that at least 2 processors are communicating properly at any point of time when boiler is in service. Failure of communication leads to malfunction of protection circuit 0 sec - INSTANT.

Purpose:

Protection Delay:

Protection Check: By actually isolating network connections of the processors.19 January 2012 PMI Revision 00 25

18. EMERGENCY TRIP Arming: Logic: Always armed If both Desk Emergency Push Buttons pressed together (OR) If both Backup Panel Push Buttons pressed together (OR) If MFT is confirmed through popup from any workstation PC

Purpose: This facility allows the operation desk engineer to directly trip the boiler in case of any operational emergency eg. Boiler Tube Leakage, Furnace excessive Clinkering, HFO oil leakage during startup, turbine related emergencies etc.

Protection Delay: Protection Check: By actually operating push buttons/through PC.19 January 2012 PMI Revision 00 26

0 sec - INSTANT.

POST-TRIP PURGE FANS TRIP Arming: Logic:

Boiler not firing fuel for 5 min (MFT may or may not be reset) If furnace pressure very high > 150 mmwc OR very low < -175 mmwc (AND) Air Flow > 30% THEN TRIP all ID Fans and FD Fans This protection safeguards furnace against furnace pressure very high OR very low when boiler is NOT firing.

Purpose: Protection Delay:

0 sec INSTANT (5 min delay in arming circuit) By simulation at source.

Protection Check:19 January 2012 PMI Revision 00 27

RUNBACK GRADED MILL TRIP Arming: Logic: More than 4 mills in service If any major auxiliary (eg. ID, FD, PA, BFP) trips and standby is not available, unit load is automatically reduced according to the new capability Mills are tripped one by one starting from top running mill, at 2 sec delay, until 4 running mills from bottom remain. This interlock achieves the fastest possible load reduction, and requires NO intervention of desk engineer Varies from 1 sec to 1 min according to type of auxiliary Simulated at initiating point.PMI Revision 00 28

Purpose:

Protection Delay:

Protection Check:19 January 2012

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THANK YOU QUESTIONS ?

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P&I OF BOILER AUXILLARIESA. FD FANSTART PERMISSIVES

Blade pitch position minimum. Discharge damper fully closed. Lube oil pressure adequate. Control oil pressure adequate. Oil tank level normal. Bearing temperature not high. One ID Fan running AND other FD fan not running. OR Both ID Fan running

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TRIPS

Fan bearing temperature very high Post purge furnace pressure very high/ very low Outlet damper fail to open in set time (3 min) No ID fan running or one ID fan and one FD fan already in service.

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PA FANSTART PERMISSIVES Blade pitch minimum Lube oil pressure adequate Control oil pressure adequate Bearing temp. not high Discharge damper closed. Lube oil tank level adequate No MFT & Cold air damper closed At least one FD fan is running and PAPH A/B in service & respective air inlet/ outlet dampers are open 19 January 2012 PMI Revision 00 33

TRIPS Fan bearing temperature very high. Trip from FSSS (MFT). Discharge damper fails to open.

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ID FANSTART PERMISSIVES Hyd. coupling Scoop position minimum. Inlet guide vane position minimum. Bearing temperature not high. Oil temp. and oil level in Hyd. coupling OK. Lube oil pressure adequate. Both inlet and outlet dampers closed. Other ID fan not running or Any FD fan running.

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TRIP CONDITION Fan/Motor bearing temperature very high. Lube oil pressure very low. Post purge furnace pressure Hi/Low from FSSS. Discharge dampers/ suction damper fail to open within specified time (3 min.) Hydraulic coupling bearing temp. very high Hydraulic coupling oil temp. very high.

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SGWC PUMPS: (CC Pumps)

PERMISSIVES Discharge valve 1 open. Discharge valve 2 open. Motor cavity temp. not high. Pump cavity suction manifold differential temp. not high. Motor cooling water flow adequate.19 January 2012 PMI Revision 00 37

TRIPS

Any of the discharge valves not fully open. Motor cavity temp. high (60 deg. C) for more than 5 Sec. Electrical protection trip/ EPB pressed.

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Run back operation Tripping of PA Fan or FD Fan PA header pressure low/very low Sequential tripping of Mills/Feeders

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