Seperator Logics

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  • 7/30/2019 Seperator Logics


    Start up system and

    seperator logics 660MW

    (DHI make) boiler

  • 7/30/2019 Seperator Logics


  • 7/30/2019 Seperator Logics




    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


    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


    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 s