Download pdf - Seperator Logics

7/30/2019 Seperator Logics

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Start up system and

seperator logics 660MW

(DHI make) boiler


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BOILER START-UP AND

OPERATIONAL PROCEDURES

Cold Start Up conditions Greater than 72 hours shutdown.

Boiler pressure < 1 kg/cm2 (g)

Preparation for BLU Chemical cleaning and steam blowing completion (for

the first time)

All interlocks and protections in service All instrumentation and associated mechanicalequipment has been checked out and is available forservice.


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Oil firing equipment checked out to ensureproper functioning

Warm-up oil guns have been inserted properly andcoupled.

All oil guns quick connect couplings are properlyassembled.

All manual valves are opened.

All control valves are closed.

Pulverisers and feeders are available forservice

SADC checking complete & burner tilthorizontal

Feedwater system is through and atleast onefeed water pump available.


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The deaerator aux. steam supply is available

and feedwater in deaerator is at 105C.

BCP checked out completely Suction and discharge iso. Valves open

All pump instrumentation available in service

Pump diff. pressure transmitters in service

Ensure proper trip settings have been made

The steam generator start-up system valves

are ready for operation (UG, WR, ZR valves),

with isolation valves open. The separator levelcontrol for WR and ZR valves has been

checked and is available for service.


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The startup system drain transfer system is ready for

operation. This system includes WR and ZR valves,

the flash tank and connecting pipe to condenser.

Steam supply isolating valves to the steam coil air

pre-heaters are open.

Cooling water system is in operation

All air and gas handling equipment has been checked

and is available for service.

Air heater ready for service & means for extinguishing

APH fire is available.

The soot blowing equipment has been checked for

proper operation and the system is in the start-up

mode with all blowers retracted and the main steam

supply valve closed.


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All desuperheater spray water control and blockvalves valves are closed.

All boiler, superheater, and reheater drain valves areopen, and all vent valves are closed. The economizerand furnace wall drain valves are closed, andeconomizer vent valves are open.

The aux. steam isolation line from the superheater is

isolated. The warming system of the boiler superheaters is

isolated.

The furnace gas temperature probe(s) is in workingorder and available for service.

The HP and LP bypass stations are available forservice, and hydraulic stations are in operation. Thewater supply for desuperheating has beenestablished.


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The condenser is available in service, with circulationwater flow and vacuum has been established toaccept water flow from Start-up flash tank and theSCAPH drain tank and LP bypass (condenserpressure set point interlock of LP bypass).

The main steam stop cum control valves and the hotreheat stop and control valves are closed. Drainvalves on the main, cold reheat and hot reheat linesare open.

The condensate polishing plant is available foroperation.

The TG has been prepared and is available forservice

Warm water filling The entire economizer, furnace wall and seperator

system should be filled with warm deaerated water(105C)


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The following procedure shall be carried out to ensurethat the water system is free of air :-

The economiser outlet vent valve is open.

BFP (M) is started at minimum speed and flow according tofeed pump operating procedures.

Water system is to be filled with approx. 10 % BMCRfeedwater flow. When level in the seperator reaches set-pt.,the WR valve will begin to open. When the WR valve reaches

> 30% open for approx. 1 min., feedwater flow set pt. isincreased to 30 % TMCR. As the drain flow increases, WRvalve will reach full open and ZR valve will begin to open.The water system is considered full when :-

The seperator water level remains stable for two minutes.

And The WR valve is fully opened and ZR valve is >15 %

opened for two (2) minutes. After filling of water system, the feedwater pump is stopped.

Water level in deaerator must be re-established andmaintained and water temperature at 105C is reestablished.


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Restart the feed water pump and establish feedwater flow of

10 % BMCR to the boiler.

Water recirculation for clean up

Feed water clean up recirculation is required to

ensure that feedwater quality at the o/l. of seperator

and deaerator is within specified limits.

During this time, a constant feedwater flow of 10 %

BMCR is maintained.

Feed water flows through

Ecomomiser and Evaporator and discharges the boiler

through the WR valve to the flash tank and via connecting

pipe to the condenser. From condenser, water flows through

the CPP, which is in service to remove impurities,then

returns to the feedwater tank.


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Start of Boiler Circulation Pump The following preparatory work needs to be completed :-

Feed water quality within specified limits.

Feed water flow set point at 10% BMCR.

Seperator water level stable at normal level. Cooling water flow to the HP cooler of BCP adequate.

Suction valves and discharge valves are open.

Set the UG valve at min. position and start BCP as per pumpoperating instructions.

As soon as pump is running, open the UG valve to establish min.

water wall flow at 30% TMCR. With BCP in operation, flow through the economiser and water

wall tubes increases substantially.

Initial firing precautions

Atleast 30% of the TMCR load air flow must be maintained toproduce the following conditions :- An air rich atmosphere to prevent accumulation of an explosive

mixture

High excess air through the APHs


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Boiler Light Up Start the Secondary Air Preheater

Start one ID fan, then the corresponding FD fan andadjust air flow to a max. of 30% TMCR

Start the second draft group

Start the selected scanner air fan.

Adjust fan and SADC to permit a purge air flow of

atleast 30% of TMCR and furnace draft of approx. -12.7 mmWC.

When fans are started, SADC should modulate theaux. air dampers to maintain WB to furnace DP at 102

mmWC(g). Check that all other purge permissives are satisfied.

Place FTPs in service.

Initiate a furnace purge.


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After furnace purge check the followingconditions

FW control is on auto maintaining FW flow rate ofapprox. 5% TMCR.

Start-up system (BCP and UG valve) is onautomatic maintaining minimum waterwall flow.

Seperator level control is on auto, i.e the WR and

ZR level control valves are all in automatic. Furnace pressure control is on auto.

Unit air flow is on auto maintaining 30% TMCR airflow.

Place HP bypass valve in operation Place LP bypass valve in operation

Place SH and RH temp. controls on auto. Withsetpoints of 350 C for SH and 320 C for RH.


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Open SH division panel vent valves, SH backpassdrain valves and RH outlet vent valves.

Initiate a light-up sequence of oil elevation AB warm-up oil guns.

Set fuel oil flow control to auto and adjust the TMCRto 5 % of TMCR firing rate.

When elevation AB is in service, close theeconomizer vent valves.

After a 5 minute stabilization period, progressivelyincrease firing rate to 10 % TMCR at a rate of 0.5%per minute.

To ensure stable operation of the water system and toensure sufficient steam flow through the superheater,firing rate shouldnot be further increased until 8kg/cm2 (g) is measured in the water seperator.


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As the pressure is raised, first the WR and then the

ZR valves will open when seperator water level

increases due to boiler water swell. As the pressure

further increases,the WR and ZR valves will start toclose as the water level decreases.

During all start-ups, control the firing rate to keep the

max. FEGT below 538 C, as measured by the

furnace temperature probes until approx. 10% steamgeneration or the turbine is synchronized.

The superheat backpass drain valve can be closed

when seperator pressure reaches 5 kg/cm2 (g).

Progressively increase LP bypass set point to 12kg/cm2(g).

Close the RH o/l. vent valves when RH pressure

reaches 5 kg/cm2.


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Increase LP bypass set pt. to 12 kg/cm2(g). As theHP bypass opens, the reheater will be warmed andpressurized cas steam is passed through the LPbypass and reheater vents.

Close the reheat outlet vent valves when RH pressurereaches 5 kg/cm2(g).

When steam pressure at HP bypass reaches 12kg/cm2(g), the HP bypass valve is released topressure ramp mode

Initiate an elevation start command for other oilelevations.

After a 5 minute stabilization period, progressivelyincrease firing rate to 15% TMCR at a rat of 0.5% perminute.

The rate of pressure rise should follow the prescribedstart up curves

When boiler pressure reaches 90 kg/cm2(A), the HPbypass valve is released to pressure control modeand maintains a constant pressure during rolling.


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After a pressure of 90 kg/cm2 is attained the firingrate can be adjusted to achieve the reqd. steamtemperature for turbine rolling. Target steamconditions are:- 10% TMCR steam flow, SH = 350 C,RH = 320 C.

Maintain seperator water level at normal and checkthe boiler water concentrations and constituents asfrequently as necessary to maintain proper boilerwater conditions.

Turbine rolling and synchronisation Confirm the steam conditions, i.e. pressure,

temperature

Roll turbine using reheat steam. During this time totalsteam passes through HP bypass while it remains onpressure control mode.

SH and RH steam temperatures are maintained byadjusting firing rate and air flow.


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Synchronize generator and put on initial load of app.10% according to TG start up instructions.

After synchronization, all superheat and reheat vent

and drain valves should be closed. As steam is transferred to the IP turbine during

turbine loading, the LP bypass will close whilemaintaining reheat pressure at 12 kg/cm2.

Increase firing rate to 20 % TMCR at a rate of 0.5%per minute.

As turbine conditions permit, put feed water heatersinto service as per manufacturers instructions.

The firing rate should never exceed the rate

necessary to match the total steam generation. If the unit was started with one set of fans in service,

start the second set of fans as required.


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Introduction of coal Coal firing can commence when steam flow reaches

approximately 20% TMCR and LP bypass is closed.

Start the first pulverizer At a prescribed load as per turbine manufacturer, the

HP turbine is transferred to forward flow. At first threeturbine control valves are opened until sufficient flowis established through the HP section of the turbine.

The HP bypass valve compensates by closing tocontrol the steam pressure at set point.

Continue the transfer to forward flow until the firstthree turbine valves are fully opened and HP bypassvalves are fully closed.

Start the second pulverizer when the HP bypass isclosed.

Increase the total firing rate to 30% TMCR at a rate of0.5% per minute by increasing each coal elevationloading.


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Initial load increase The third pulverizer can be started after steam flow

reaches 25-30% TMCR. Place additional pulverizers

in service in a similar manner. Pre-warm thepulverizer initiate an elevation start command. Afterthe coal elevation is proven in service the feeder isput into automatic.

Increase total firing rate to 35% TMCR.

After reaching 30% TMCR load and firing is stable, oilelevation AB is issued an elevation stop command bythe operator

After oil elevation AB is stopped ensure that coal el. Aor C shows flame through flame scanner indications.

Reduce oil firing to minimum After stable firing is established, put into service the

second BFP(T) as per manufacturers procedures.

Start the ESP as per manufacturers instructions.


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The steam temperature at the seperator inlet will

reach a stable superheated condition at

approximately 30% TMCR, causing the level in the

seperator to decrease and eventually disappear. The

boiler is now in once-through mode (dry mode). The

BCP will be stopped automatically.

When the BCP stops, the warm-keeping system of

the start-up system should be put into operation.


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Wet mode and Dry mode of operation


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Operational Logics for Mixing Piece Upstream

Valve orBCP circ. Shut-off MOV

Open permissive If WET mode of operation is selected AND

DRY mode is not selected

Close permissive

BCP off Auto opening

Open permissives present AND any of the following conditionsare present

MFT has operated OR

Open command from start sequence for BCP circ. Shut off valve(Mixing piece upstream valve) OR

System in wet mode of operation for 3 seconds

Auto closing If system is in dry mode of operation for 3 seconds.


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Operational logics for Boiler

recirculation Pump

Start permissive UG valve opening > min. (15 %)AND

BCP circ. Shutoff MOV openedAND

BCP inlet shut off MOV openedAND

BCP outlet shut off MOV openedAND

BCP inlet manual valve openedAND

BCP cooling water flow not lowAND

Seperator storage tank level > 1100 mm AND

Economiser inlet flow > 111 T/hrAND

No BCP trip override existsAND

No BCP MCC disturbance exists


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Trip permissives

Dry mode of operation of the boiler

Auto starting of BCP

BCP will get auto started if either BCP auto

start signal is present OR

Start BCP FR. W & steam start seq. signalfrom Start seq. is present.

BCP auto Start signal


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Auto stopping of BCP

BCP will stop on auto if either BCP auto stop

signal OR BCP MCC disturbance signal ispresent.


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BCP trip override logic


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Operational logics for BCP Inlet

Shut-off MOV Open permissive

If WET mode of operation is selected OR

BCP not tripped

Close permissive

BCP not running (stopped) Auto opening

Open permissives presentAND any of the following conditionsare present

MFT has operated OR

Open command from start sequence for BCP inlet shut off MOV OR System in wet mode of operation for 3 seconds OR

BCP auto start signal is present

Auto closing BCP trip signal


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Operational logics forBCP Outlet

Shut-off MOV Open permissive

If WET mode of operation is selected OR

BCP not tripped

Close permissive

BCP not running (stopped) Auto opening

Open permissives presentAND any of the following conditionsare present

MFT has operated OR

Open command from start sequence for BCP outlet shut off MOVOR

System in wet mode of operation for 3 seconds OR

BCP auto start signal is present

Auto closing

BCP trip signal


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Operational logics forBCP

Circulation Line Vent MOV Open permissive

If Auto Dry Mode of operation is not selectedAND

If BLI is less than 15 % BMCR OR BCP is notrunning

Auto opening Open permissives present and also if any of thefollowing conditions are present

MFT has operated OR

Open command from start sequence for BCP circ. Line ventMOV OR

BCP is not running

Auto closing If Auto Dry Mode of operation is selected OR

If BLI > 15 % BMCR and BCP running (proven for 20

secs.

Operational logics for WR Line


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Operational logics for WR Line

Isolation MOV Open permissive

If BLI is lesser than 1000 T/hrAND Either Main steam bottle up OFF OR

All feedwater pumps not off.

Close permissive BLI > 960 T/hrOR

If all FW pumps are offAND BCP is offAND all scanners show no flame

Auto opening Open permissives presentAND also if any of the following conditions are present MFT has operated OR

Open command from start sequence for WR line isolation MOV OR

Auto wet mode of operation OR

Seperator storage tank level > 1100 mm OR

BLI < 890 T/hr.

Auto closing BLI >1000 T/hrOR Main steam bottle up ONAND All feedwater pumps off

Manual close After manual control is enabled, this will take place

If Manual close command is sent from LVS / OWSAND

Seperator storage tank level is not greater than 1100 mm.

Operational logics for ZR Line


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Operational logics for ZR Line

Isolation MOV Open permissive

If BLI is lesser than 1000 T/hrAND Either Main steam bottle up OFF OR

All feedwater pumps not off.

Close permissive BLI > 960 T/hr OR

If all FW pumps are offAND BCP is offAND all scanners show no flame

Auto opening Open permissives presentAND also if any of the following conditions are present MFT has operated OR

Open command from start sequence for ZR line isolation MOV OR

Auto wet mode of operation OR

Seperator storage tank level > 1100 mm OR

BLI < 890 T/hr.

Auto closing BLI >1000 T/hrOR Main steam bottle up ON AND All feedwater pumps off

Manual close After manual control is enabled, this will take place

If Manual close command is sent from LVS / OWSAND

Seperator storage tank level is not greater than 1100 mm.


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Operational logics forStorage tank drain MOV /

Seperator water leg level control blocking MOV

Open permissive

Dry mode of operation

Auto opening

If seperator water leg control valve demand > 5 %.

Auto closing

Close seperator water leg CV demand from Start

sequence. OR

MFT operated OR

BCP on and Wet mode of operation OR

Seperator water leg CV demand < 2%AND

Close position < 5 %.


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Operational logics for Start up

system warming MOV

Open permissive Dry mode of operation

Auto opening

Open permissives presentAND also if any of thefollowing conditions are present Seperator storage tank level is less than 4000 mm

Auto closing If wet mode of operation OR

If MFT gets operated OR

Close start up system warming valve command ispresent from Start up sequence. OR

Seperator storage tank level > 1100 mmAND BCP

On.


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Operational logics for BCP Drain

MOV

Open permissive

BCP not running

Auto closing

BCP running

Operational logics for BCP outlet

drain MOV Open permissive BCP not running

Auto closing

BCP runnin


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Separator logic (Seperator storage tank wet leg level)


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Separator logic (Seperator storage tank wet leg level)

Separator logic (Seperator storage tank level)


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Separator logic (Seperator storage tank level)

Separator logic (Control of flow through BCP)


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Separator logic (Control of flow through BCP)


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