BOILER PURGE CONTROL

The following permissive must be met before boiler purge can take place.

All Pulverizer Primary Air On-off type dampers Closed Both PA Fans stopped Total Boiler Air Flow at Purge Rate Either Forced Draft Fan Running and either Induced Draft Fan running. Secondary Air Heater Running All oil igniter group SSVs closed Igniter oil header SSV closed All oil burner SSVs closed Oil header SSV closed All Coal feeders stopped All Pulverizer Swing Valves Closed All Coal Pulverizers Stopped All air register Dampers at Light-off Position No MFT Trip Condition Present (excludes steam drum level low / high) MFT relay tripped. Open flow path to stack proven.

Once these permissive met and continuous purge air flow rate maintained, a purge timer willstart & continue for required Purge period and indicate for PURGE COMPLETE

MASTER FUEL TRIP

MFT INPUT: Steam Drum Level Not Low Low Steam Drum Level Not High High Main steam temperature Not High High Furnace Pressure Not High-High Furnace pressure Not Low Low Total Boiler Air Flow less Than Minimum Any Forced Draft Fan Running (Instantaneous) Any Induced Draft Fan Running (Instantaneous) Boiler Control System OK Burner Management System OK MFT Relay System Energized (Instantaneous) MFT Switch Not Activated from field hardwired, MFT Pushbutton Not Activated (software) Black furnace trip All igniter group successfully Shutdown or tripped. All Pulveriser groups successfully shutdown or tripped. All oil burners successfully shutdown or tripped.

MFT OUTPUT:

When the MFT is activated, the following fuel input devices shall be simultaneously DE energized/ closed : Igniter oil Header Safety Shutoff Valve (SSV) All Individual Igniter Group Ignition Transformers All Individual Igniter Group Oil SSVs All Individual Igniter Group Atomizing SSVs All Individual Igniter Group Clearing SSVs Main oil Header Safety Shutoff Valve (SSV) (& open recirculation valve) All Individual Burner Oil SSVs All Individual Burner Atomizing SSVs All Individual Burner scavenging SSVs All Coal Feeders All Coal Pulverizers All PA isolation dampers at mill inlet All Individual Pulverizer Group Swing Valves Boiler Control System (DCS) (To close Primary Superheat Block Valve, SecondarySuperheat Block Valve, set the fuel control to minimum position, and Stop both PA fans,Stop seal air fans and close the PA Fan dampers)

BOILER FIRING PERMISSIVES: Purge Complete Flame Scanner Cooling air pressure not low Ignitor cooling air pressure not low Total boiler air flow greater than or equal to 25 percent No Furnace Firing Inhibit Present

The Furnace Firing Inhibit is activated for one minute duration when any of the followingcondition occurs: Trip of any igniter group when the associated Pulverizer Group Main (coal) Fuel Monitoring Mode is not activated. (See Pulverizer Group Start Sequence section of this Document) AND Boiler Load is less than 50% Start of any Igniter Group AND Boiler load is less than 50% Start of any Oil Burner AND Boiler load is less than 50% Any oil burner trip AND Boiler load is less than 50% Start of any coal feeder Any pulverizer group Emergency Trip Start of any Igniter GroupThe Furnace Firing Inhibit is activated for 15 seconds duration when boiler load is greaterthan 50% & any of the following condition occurs: Trip of any igniter group when the associated Pulverizer Group Main (coal) FuelMonitoring Mode is not activated. Start of any Igniter Group. Start of any Oil Burner. Any oil burner trip.

FLAME MONITORING AND TRIPPING:

Ignitor in a group of three and each flame must be healthy after ignitor group command. For oil burners individual burners flame must be healthy. For coal flame 2/6 logic or ignitor in service.BURNER AIR SLIDE (AIR REGISTER) DAMPER CONTROL:

Each burner sliding air dampers is positioned by a 4-20 mA DC Linear Pneumatic Actuator &Burner sliding air dampers position transmitter. The Burner Management System includesanalog input and analog output interface devices.

Cooling Position: provides cooling air while the burner is out of service.

Light-off Position: During igniter operation and during pulveriser group / oil burner isin start-stop sequence.

Firing PositionSliding air dampers has two firing positions viz. Coal firing position and Oil firing position. Oilfiring position is wide open than coal firing position. The BMS shall automatically position theBurner Sliding Air Dampers to the firing positions when all of the following conditions occur: Coal Firing Position Oil Firing Position

Allow Burner Sliding Air Damper Positioning. All Burner Sliding Air Dampers are locked in last position for 2 minutes whenever MFT activated and total Boiler Air Flow greater than or equal to 30 percent

All Burner Sliding Air dampers are locked in last position for 5 minutes whenever MFT activated and total Boiler Air Flow less than 30 percent.

All Burner Sliding Air Dampers are locked in last position for 1 minutes and a 15-minute when Natural Draft is required when the Both Induced Draft Fans or Forced draft fans stopped within 5 minutes after a MFT is activated..IGNITER OIL HEADER SAFETY SHUTOFF VALVE:

The Igniter Header control logic shall include the opening and closing of the safety shutoffvalve (SSV) for the igniter oil header which results supply of LDO to all igniter groups. Theigniter oil header contains three (3) pressure transmitters, one no. safety shut-off valve (SSV).

When the following permissives are met, operator may open igniter oil header SSV viaOperator Station (OS): Boiler Firing Permissive Satisfied Igniter Oil Header SSV Closed All Individual Igniter Group Oil SSVs Closed Igniter Oil Header SSV not Commanded (interlocked) Closed Igniter Oil Header Not TrippedThe operator can close the Igniter Oil Header SSV anytime (via OS), if it is in the openposition. The Igniter Oil Header SSV shall be interlocked to remain in closed conditionautomatically when any of the following conditions occur: Operator Activated the Close Igniter Oil Header SSV Pushbutton (via OS) Igniter Oil Header Trip Activated. MFT ActivatedIgniter Oil Header Trip shall be activated when any of the following conditions occur: Igniter Oil Header pressure low . Any Igniter Group Flame Not detected and Associated Igniter Group SSV Failed to Close Igniter Atomizing Media Header Pressure Low. Igniter Oil Header SSV Failed To Close (10 second delay)

IGNITER GROUP CONROL:Igniter group AF -- elevation A front side.Igniter group BF -- elevation B front side.Igniter group CF -- elevation C front side.Igniter group DF -- elevation D front side.Igniter group AR -- elevation A rear side.Igniter group BR -- elevation B rear side.Igniter group CR -- elevation C rear side.Igniter group DR -- elevation D rear side.

Igniter Group Tripped/StopAn igniter group trip shall be generated if any of the following occurs during starting, shutdown/ cleaning, or when the igniter group is in service : Igniter group atomizing pressure not adequate (low) (5 second delay) Igniter group SSV failed to close (10 second delay) Igniter group SSV failed to open (10 second delay) Igniter group atomizing air SOV failed to close (10 second delay) Igniter group atomizing air SOV failed to open (10 second delay) Igniter group purge SOV failed to open (10 second delay) Igniter group purge SOV failed to close (10 second delay) Igniter group any flame failure (any associated flame not detected and igniter group trial for ignition period completed) Igniter group emergency stop pushbutton activated Associated Pulveriser group trips on emergencyoperator may stop an igniter group anytime it is in the process of starting or in service. Pulverizer group emergency trip pushbutton pressed (via OS) Operator activated the stop igniter group pushbutton (via OS) Pulverizer group start sequence requires to stop associated igniter groups.\ MFT activated Any oil burner sequence requires stop igniter.

Clearing (Cleaning) the Igniters:Once the Igniter group is stopped due to any of the above mentioned conditions, it closesigniter Oil SSV immediately. However atomizing air SSV continues in open condition forclearing cycle unless igniter group is tripped.

OIL BURNER HEADER SAFETY SHUTOFF VALVE:

The oil burner header (Note: wherever mentioned header implies to common header toburners) control logic shall include the opening and closing of the safety shutoff valve (SSV)for the oil burner.

The operator may open, via Operator Station (OS), the oil burner header SSV when thefollowing permissives are met: Oil Burner firing permissives satisfied Oil burner header SSV closed All individual oil burner SSVs closed Oil burner header SSV not commanded (interlocked) closed Oil burner Header recirculation valve closed.The operator may close (via OS) the oil burner header SSV anytime it is in the open position.The oil burner header SSV shall be interlocked closed when any of the following conditionsoccur : Operator activated the close oil burner header SSV Pushbutton (via OS) Oil burner header trip activated MFT activated Differential pressure between oil & atomizing header very low when header SOV not closed or any oil burner SSV not closed (7 second delay) An oil burner header trip shall be activated when any of the following conditions occur ( i.e. all the running oil burners will trip): Oil burner header pressure low with oil burner header SSV not closed OR any Oil Burner SSV Not Closed (7second delay) Oil burner header temperature low with oil burner header SSV not closed OR any Oil Burner SSV Not Closed (7second delay) Any oil burner flame not detected and associated oil burner SSV failed to close Oil burner header SSV failed to open (7 second delay) Oil burner header SSV failed to close (7 second delay)

OIL BURNER HEADER RECIRCULATION SHUTOFF VALVE :

Once main oil header SSV is confirmed closed (with delay of 2 seconds) then recirculationSSV is opened if any of the following conditions are active: Operator open the recirculation SSV through command on OS. All oil burner SSVs closed. Master fuel trip activated Main oil header SSV close required.Recirculation SSV shall close automatically if the main header line SSV is commanded open /not in closed condition. Also, if MFT is not activated then operator can manually close therecirculation valve.

OIL BURNER CONTROL:The oil burners are controlled individually. Initiating an oil burner start or stop sequence willinitiate the corresponding igniter group start sequence. The igniter group for a particularburner group must be successfully lit before main fuel for a particular burner can be fired.

The burner oil firing permissives are satisfied when all of the following conditions occur : Boiler firing permissives satisfied. Burner oil header SSV commanded to open and is confirmed open. Atomizing steam common header pressure not low (2oo3) Burner oil header trip reset Any FD fan Running Oil burner gun retracted Oil burner trips reset Oil burner firing selected Igniter group ready to start or in service Oil burner firing permissives satisfied Oil burner atomizing SOV closed and corresponding scavenging SOV closed Oil burner SSV closed Flame scanner permissive satisfied Pulverizer Isolated Oil Burner clean Oil burner not in Start / Running sequence. Burner main flame not detected OR unit load greater than 60% OR Igniter groupsuccessfully litAfter all permissives are satisfied, a Burner Ready indication is generated and the operatorcan start the burner. The following sequence will proceed automatically. Open PC pipe (nozzle) cooling air valve and confirm it is open Set burner secondary air register at light-off position Start igniter group (if not in service) Confirm igniter group in service Insert Burner Oil Gun and Confirm Insertion Open Oil Burner atomizing steam SOV and confirm that it is open Open the oil burner SSV and confirm that it is open Begin burner trial for ignition (5 seconds) after fuel actually begins to enter the furnace Oil burner successfully lit. Position burner secondary air register to oil firing position Stop the corresponding igniter group when a time of Five minutes is elapsed afterstart memory for oil burner is set. Additionally Stop the corresponding igniter groupimmediately when all three oil burners are in service.

A given oil burner is considered successfully lit when all of the following conditions are met : No Oil burner trip condition present Trial time (5 second elapsed) for ignition complete Burner flame detected Burner oil gun (assembly) inserted Burner oil SSV open Burner atomizing SOV open Burner PC pipe cooling air valve open.

Oil Burner Trip:

If any of the following conditions occur, an oil burner trip shall be generated Operator pressed the oil burner emergency stop pushbutton. Igniter group stopped during oil burner gun (scavenging) clearing Oil burner flame failure (burner flame NOT DETECTED AND TRIAL TIME for ignition timed out) Oil burner SSV failed to open (10 sec delay) Oil burner SSV failed to close (10 sec delay) Oil burner failed to insert (10 sec delay) Oil burner failed to retract (10 sec delay) Oil burner atomizing SOV failed to open (10 sec delay) Oil burner atomizing SOV failed to close (10 sec delay) Oil burner scavenging SOV failed to open (10 sec delay) Oil burner scavenging SOV failed to close (10 sec delay) Oil burner start / stop sequence requires corresponding igniter group and the igniter group failed to start Burner PC pipe cooling air valve failed to close Burner PC pipe cooling air valve failed to open Oil header steam DP low AND oil burner atomizing valve open Burner oil valve open & Oil header SSV close requiredWhen an oil burner trips or a master fuel trip occurs, all of the following conditions will occur.In this case, oil gun scavenging sequence is not initiated automatically. Close the oil burner oil SSV Close the oil burner atomizing SOV Close the oil burner scavenging SOV

Stopping the Oil Burner:

The operator can stop an oil burner at any time by activating the oil burner stop pushbutton.The stop oil burner command shall initiate the following sequence automatically and stop theburner. This sequence is also termed as Scavenging (Oil gun cleaning) sequence. Start igniter group. Allow 15 seconds to confirm igniter group is in service Close the oil burner SSV and confirm that it is closed Set burner air register to light-off position Open the oil burner scavenging SOV (if scavenging cycle is not blocked) Hold for 3 minutes for scavenging the burner oil gun Close the oil burner atomizing steam SOV and confirm that it is closed Close oil burner scavenging SOV and confirm that it is closed Retract burner oil gun. Close the PC pipe cooling air valve. Stop the corresponding igniter group when duration of Five minutes is elapsed.after Burner Stop memory set. Additionally Stop the corresponding igniter groupimmediately when all oil burners are successfully shutdown.

Scavenging the Oil Burner:The oil gun is considered dirty as soon as the oil SSV is opened during burner start sequence.During stop sequence of oil burner, the scavenging cycle is performed in auto sequence, aftercompletion of which the oil gun is considered as clean.The oil burner scavenging cycle can be initiated when all of the following conditions occur : Oil burner dirty Oil burner scavenging cycle not blocked Operator activated the oil burner stop pushbutton via the DCSWhen the operator initiates the oil burner scavenging cycle via the oil burner stop pushbutton,the following sequence will occur: Start igniter group Allow 15 seconds to confirm igniter group is in service set burner air register to light-off position Insert burner oil gun if it is not inserted. Open the oil burner scavenging SOV Hold for 3 minutes to scavenge (purge) the Burner Oil gun Close the oil burner atomizing steam SOV and confirm that it is closed Close oil burner scavenging SOV and confirm that it is closed Retract burner oil gun Close the PC pipe cooling air valve Stop the corresponding igniter group when all oil burners are successfullyshutdown or tripped and the Maintain igniter group memory is reset.A burner oil gun (scavenging) cleaning cycle is blocked when any of the following conditionsoccur: Oil burner tripped Master fuel trip activated Operator pressed the start oil burner pushbutton (momentary) Oil burner header steam to oil differential pressure low Oil burner gun retractedThe burner oil gun (scavenging) clearing cycle blocked memory is reset when any of thefollowing conditions occur: Oil burner start sequence running / Burner lit. Oil burner trip reset.The oil burner will not retract automatically when the oil burner scavenging (clearing) cycle isblocked. However, the operator can retract the oil burner by pressing the Retract Oil Burnerpushbutton (OS) when all of the following conditions are satisfied Oil burner oil SSV closed Oil burner atomizing SOV closed Oil burner scavenging SOV closed Oil burner scavenging blocked for more than 30 seconds.Once Oil gun is retracted, the PC pipe cooling air valve shall close automatically.A burner is successfully shutdown when all of the following conditions occur: Oil burner retracted Oil burner SSV closed Oil burner Clean Oil burner atomizing SOV closed Oil burner scavenging / clearing SOV closed

OIL BURNER SEQUENTIAL START IN AUTO:Elevation all (six) Oil Burner can be started in auto sequence with operator intervation.This facility is provided to meet the boiler demand in short period of time.

PULVERIZER GROUP CONTROL:

There are four pulverizer groups (A, B, C and D), all burners in a pulverizer group arecontrolled as a group. Each burner is equipped with a swing valve. All six (6) swing valvesassociated with a pulverizer group shall be opened and closed at the same time. Starting andstopping individual burners in a pulverizer group is not permitted.A remotemanual isolation valve (pneumatically operated) is installed in each burner line (coalpipe) as close to the furnace as practicable, which is operated by operator when required formaintenance.

The pulverizer seal air fan, PA fan(s)and lube oil pump should be started as the initial steps before placing the pulverizer group inservice.

A pulverizer group can be operated in a manual or automatic sequence control mode.

Pulverizer Group Equipment Permissives Pulverizer not tripped Coal Feeder not Tripped MFT activated Pulverizer Group Emergency trip activated PA Flow Tripped(PA flow isolation damper is not tripped, Either PA fan running)

Operator activated the pulverizer group stop sequence pushbutton (via OS)

Pulverizer lube oil temperature above minimum & less than maximum Pulverizer lube oil pump running Pulverizer lube oil pressure not low low All PC pipe isolation valves are open Pulverizer Lube Oil System Parameter healthy. All oil burners SSV closed & nozzle / purge air valve closed. Coal feeder equipment permissive satisfied.

Pulverizer Group Start SequenceAn operator initiated (via OS) START pulverizer Group A command shall activate the followingstart sequence SET the pulverizer group demand to minimum. SET Burner group Sliding Air dampers to Light-off position. START associated lgniter group AND confirm igniter group in-service. START pre-start inert (required when the pulverizer was stopped prior to completing anormal cleaning cycle, CONFIRM pre-start inert is completed.. OPEN pulverizer yoke Seal Air Valve and confirm that the Valve is open OPEN pulverizer roll Wheel Seal Air valve and confirm that the valve is open & seal airpressure is adequate. OPEN coal feeder seal air valve and confirm that the valve is open & seal air pressureis adequate. OPEN pulverizer primary air On-off damper and confirm that the damper is open OPEN pulverizer group swing valves (quantity 6) and confirm that the valves are open Wait 10 seconds to Establish primary air flow. OPEN coal feeder inlet valve and confirm that it is open (part of coal feeder equipmentpermissive) OPEN coal feeder discharge valve and confirm that the valve is open START pulverizer motor. Wait 10 seconds for pulverizer motor to ramp up to speed Confirm coal feeder demand at minimum START coal feeder and confirm that feeder is running RELEASE primary air hot and tempering dampers to automatic temperature control Wait 3 minutes for initial coal flame stabilization SET burner Group sliding Air damper to firing position (Qty. 6) RELEASE Pulverizer group demand to Automatic Control Wait 5 minutes for final coal flame stabilization STOP associated Igniter Groups when all of the following conditions occur (operator action only) : Unit load greater than 25 percent Pulverizer in Auto mode. Pulverizer group A in service Secondary air temperature greater than 149degC Maintain igniter group mode de-activated. Pulverizer final coal flame stabilization period complete.

Pulverizer Group stop sequence:

An operator initiated STOP Pulverizer group A command (via OS) shall activate the followingsequence : START associated igniter Group A AND confirm igniter Group A IN-SERVICE REDUCE Pulverizer group A demand to MINIMUM CLOSE primary hot air damper AND confirm primary tempering air damper NOTCLOSED WAIT 5 minutes for Pulverizer A cooling STOP coal feeder A AND confirm coal feeder stopped SET Burner Group sliding air dampers to light-off position CLOSE coal feeder A discharge valve and confirm that it is closed WAIT 10 minutes for initial pulverizer A cleaning STOP pulverizer A AND confirm pulverizer stopped Maintain PA flow unit pulverizer A outlet temperature decreases below 60 Deg Cfor greater than 2 minutes CLOSE all pulverizer group a swing valves (quantity 6) STOP primary air flow (CLOSE the primary air on-off type damper) STOP associated Igniter group A (only if Maintained Igniter Group de-activated) SET Burner sliding air dampers to COOLING position (operator action when boilerload conditions and register permissives are satisfied)

Pulverizer group A is interlocked to stop when any of the following conditions occur Pulverizer A Tripped Coal Feeder A Tripped Master Fuel Trip activated PA Flow A Tripped Pulverizer Group A Emergency Trip activated Operator activated the stop pulverizer group A pushbutton (via OS)

Coal Feeder Start / Stop:

Coal feeder is considered READY to start when all of the following permissives areSATISFIED Boiler firing permissives satisfied Coal feeder A NOT TRIPPED Pulverizer group emergency trip reset Pulverizer group demand at MINIMUM Pulverizer RUNNING Greater than 10 seconds Coal feeder inlet valve OPEN Coal Feeder outlet not plugged Coal feeder in remote mode Coal feeder seal air pressure greater than MINIMUM Coal feeder discharge gate open Associated igniter group in-service Pulverizer group burner sliding air damper at light-off position.

The coal feeder trip shall be generated when any of the following conditions occur:

Coal Feeder running and coal feeder discharge valve closed Coal Feeder commanded to start and greater than 1 Burner swing valve closed Coal feeder failed to start (10 second delay) Coal feeder failed to stop (10 second delay) Coal feeder commanded to start and discharge chute plugged (2 second delay) Coal feeder commanded to start and local mode selected Coal feeder commanded to start and either igniter group not in-service or no coal onbelt for greater than 2 minutes