startup and shutdown procedure

M I N I S T RY O F E N E R G Y IRAN POWER DEVELOPMENT CO.

I P D C PROJECT :

22 COMBINED CYCLE POWER PLANTS YAZD COMBINED CYCLE POWER PLANT

START UP / SHUT DOWN DESCRIPTION

FOR APPROVAL

B

FOR APPROVAL

D.K.JUNG

Dec.12 ’05

S.D.CHOI

Dec.12 ’05

J.B.KIM

Dec.12 ’05

A

FOR APPROVAL

K.M.SEO

Aug.16 ’04 S.D.CHOI

Aug.16 ’04

J.B.KIM

Aug.16 ’04

0

FOR APPROVAL

K.M.SEO

Feb.04 ’04

S.D.CHOI

Feb.04 ’04

J.B.KIM

Feb.04 ’04

REV

DESIGNATION

DESIGN

DATE

CHKD

DATE

APPROVED

DATE

MAPNA C o . ( PRIVATE JOINT STOCK ) IRAN POWER PLANT PROJECTS MANAGEMENT Co.

DOCUMENT NO. : MP-YZC-IM-04-IGO-002

REV.

CONTRACT NO. :

PAGE 1 OF 16

22-0701/BA/TL

B

ORIGINATOR

ORIGINATOR NO. : YZC-M-SP-690-STT-001

DOOSAN HEAVY INDUSTRIES & CONSTRUCTION CO.,LTD.

ORIG LOC.

ORIG. PROJ. DISC. DOC. AREA SYS. DEPT. NAME TYPE TYPE FA.N

SEQ. N.

SH. N.

REV.

B

M I N I S T RY O F E N E R G Y IRAN POWER DEVELOPMENT CO.

I P D C 22 COMBINED CYCLE POWER PLANTS YAZD COMBINED CYCLE POWER PLANT

PROJECT :

PAGE

REVISION 0

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MAPNA C o . ( PRIVATE JOINT STOCK ) IRAN POWER PLANT PROJECTS MANAGEMENT Co.

REVISION 0

A

B

C

D

E

F

G

REMARKS

DOCUMENT NO. : MP-YZC-IM-04-IGO-002

REV.

CONTRACT NO. :

PAGE 2 OF 16

22-0701/BA/TL

B

ORIGINATOR

ORIGINATOR NO. : YZC-M-SP-690-STT-001

DOOSAN HEAVY INDUSTRIES & CONSTRUCTION CO.,LTD.

ORI G ORIG. PROJ. DISC. DOC. AREA SYS. LO DEPT. NAME TYPE TYPE FA.N C.

SEQ. N.

SH. N.

REV.

B

DOOSAN HEAVY INDUSTRIES & CONSTRUCTION CO., LTD. Project Name : 22 COMBINED CYCLE POWER PLANT (YAZD)

Start up / Shut down Description

TABLE OF CONTENTS 1.0

GENERAL

2.0

HRSG START UP SEQUENCE

2.1

HRSG Ready to Start

2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.2.6 2.2.7 2.2.8 2.2.9 2.2.10 2.2.11

Lead HRSG Start-up Purge of Boiler Proper GT Load for Lead HRSG Start Diverter damper operation HP and LP steam isolation valve operation HRSG SH Vent HRSG SH Drain, HP SH desuperheater Drain and Steam line drain HRSG HP & LP drum CBD/IBD drain ST HP/LP inlet warmup operation HP bypass steam system operation GT Load Increase Duct burner Load Increase

2.3 2.3.1 2.3.2 2.3.3 2.3.4 2.3.5 2.3.6 2.3.7 2.3.8 2.3.9 2.3.10 2.3.11 2.3.12

Lag HRSG Start-up Lag GT to Start Purge of Boiler Proper GT Load for Lead HRSG Start Diverter damper operation HP and LP steam isolation valve operation HRSG SH Vent HRSG SH Drain, HP SH desuperheater Drain and Steam line drain HRSG HP & LP drum CBD/IBD drain ST HP/LP inlet warmup operation HP bypass steam system operation GT Load Increase Duct burner Load Increase

3.0

HRSG SHUTDOWN & TRIP SEQUENCE

3.1

Lead HRSG Shutdown

3.2

Lag HRSG Shutdown

3.3

HRSG trip

PAGE 3

Rev. :

B


Rev. :

B


1.0

GENERAL These descriptions provide the functional requirements for the start-up and shutdown of the HRSGs and Auxiliaries for YAZD combined cycle power project. Also the descriptions are intended for the initial development of the start-up and shutdown description of the HRSGs and Auxiliaries. And overall plant start-up and shutdown descriptions shall be prepared by MAPNA using this start-up and shutdown description for HRSG and Auxiliaries and the other equipment such as gas turbine, steam turbine, cooling system etc. When developing the overall plant start-up and shutdown descriptions, this descriptions for HRSGs and Auxiliaries shall be adjusted to coordinate the other equipment. In YAZD power station, the DCS, which is supplied by Others, will be designed so as to allow the normal operation of the Plant (including start-up, shutdown and load variations) to be performed from the Central Control Room automatically and/or as per operator’s discretion. It is assumed that the hogging steam, sealing steam and holding steam must initially be made by the Lead GT/HRSG, which are tapped of HP steam common line respectively. Vacuum raising must occur following achievement of a source of steam seal supply. The operation of duct burner system will be initiated at the minimum GT load required by duct burner supplier.

2.0

HRSG START UP AND SHUTDOWN SEQUENCE

2.1

HRSG Ready to Start z z z z z z z

GT is running at minimum speed or low load to be needed for purging of HRSG. Duct burner system (HHA10AV001) is ready for start. HRSG diverter dampers (HNA01AA001) are on auto and fully open to the bypass stack. HRSG diverter damper seal air blower (HNA01AN001,002) is running and bypass stack seal air valve (HNA01AN005) is on auto and the valve close and HRSG seal air valve (HNA01AN006) is on auto and the valve open. Guillotine dampers (HNA01AA002) are on auto and fully open, guillotine damper seal air fan running. HP, LP drum and FW storage tank level controllers are on auto HP, LP drum and FW storage tank level controller set points are at their startup levels, which are dependent on drum configuration and pressure at start (HP drum : -715mm, LP drum : -485mm, FW storage tank : +685mm based on drum center line). Generally for cold startup, drum water level of above 100 mm above the LLWL point is adequate . In addition, warm and hot start up level of each Drum would be Center line of drum. PAGE 4


Rev. :

B


z z z z z z z z z z z z z z z z z z z z z z

HP, LP drum and FW storage tank levels are within allowable deviation from the startup set points. One HP/LP feedwater pump (LAC10AP001 or 002) are running and one on standby Deaerator pegging steam pressure controller is on auto HP SH attemperator spray temperature controller is on auto HRSG blowdown tank temperature controllers are on auto There are no HRSG trip conditions HP steam outlet isolation valve (LBA30AA053) is on auto and the valve is closed. LP steam outlet isolation valve (LBB20AA054) is on auto and the valve is closed. HP feedwater isolation valve (LAC30AA051/LAC50AA051) is on auto and the valve is opened. LP feedwater isolation valve (LAC40AA051/LAC60AA051) is on auto and the valve is opened. HP attemperator water isolation valve (HAH33AA051) is on auto and the valve is closed. HP and LP steam start-up vent valves (LBA30AA051, LBB20AA052) are on auto and the valves are closed. Deaerator vent valve (HAD80AA051) is on auto and the valve is opened. HP SH drain valves (LBA30AA052) are on auto and the valves are closed LP SH drain valves (LBB20AA053) are on auto and the valves are closed. HP drum intermittent blowdown isolation (HAD40AA051), continuous blowdown isolation valve (HAD35AA051) and HP drum cascade drain valve (HAD35AA052) are on auto and the valves are closed. LP intermittent blowdown isolation (HAD60AA051) and continuous blowdown isolation valve (HAD55AA052) are on auto and the valves are closed. FW storage tank intermittent blowdown valve (HAD90AA051) is on auto and the valve is closed. HP SH outlet drip leg drain valves (HAH32AA051, HAH33AA051) are on auto and the valves are closed. HP and LP steam outlet drip leg drain valves (LCM50AA051 and LCM60AA051) are on auto and the valves are closed. Blowdown tank temperature control is on auto. Auxiliary steam pressure and temperature control is on auto and controlled at the normal operating condition (15 bara, 240℃) by Aux. boiler.

If all these conditions above are satisfied, the HRSG is “Ready to Start”. HRSG may be lined-up as follows; z z z

Ensure that HRSG and duct are cleared of men and materials and that manholes and inspection holes are closed tightly. Ensure that safety valves (LAC90AA191, HAD30AA191,192, LBA30AA191,192, HAD50AA191,192, LBB20AA191,192, LCB80AA191, HAD80AA191,192) are not gagged. Local drum level gauges (HAD30CL501,502, HAD50CL501,502, HAD80CL501,502) are in service. PAGE 5


Rev. :

B


Note; Before starting the HRSGs, the following conditions for Mechanical Auxiliary/Balance of Plant(MA/BOP) Equipment shall be satisfied z z

All other systems and/or equipment supplied by GTG supplier and/or related equipment suppliers shall be ready to start condition. And this section shall be confirmed by MAPNA and/or GTG supplier. All other systems and/or equipment supplied by STG supplier and/or related equipment suppliers shall be ready to start condition. And it shall be confirmed by them.

Before starting the HRSGs, the following conditions for Mechanical Auxiliary / Balance of Plant(MA/BOP) Equipment shall be satisfied. z z z z z z z z z z z z z z z z

Auxiliary boiler is in operation One condensate pump (ALCN11AA001/ALCB12AA001) is running and one on standby Instrument air system is in service and instrument air pressure is not low. Plant air system is in service Closed cooling water system is in operation Chemical feed systems is in operation Sampling system is in operation HP and LP bypass water spray isolation valves open Mechanical Auxiliary/BOP controllers on auto CEP min. recirculation flow controller is on auto and the valve is open. Condensate dump level controller is on auto and the dump valve is closed. Motor operated valve status are O.K (Refer to the position table of MOVs specified in page 3 of SSFD (Startup/Shutdown Flow Diagram)). HP steam header drain valve (ALCM70AA051) is on auto and the valves are closed LP steam header drain valve (ALCM80AA051) is on auto and the valves are closed Electrical power supply system is O.K. All other systems and/or equipment supplied by the related equipment suppliers shall be ready to start condition. And it shall be confirmed by them.

PAGE 6


Rev. :

B


2.2

Lead HRSG Start-up

2.2.1

Purge of Boiler The compressed air from the Gas turbine will be used to purge and the purge air will go through the bypass stack. Cold Purge (GT Gas Oil or Natural Gas Fired)

Establish a minimum speed with exhaust gas temperature after turbine and before boiler < 150°C (The speed must be high enough to get rid of potential unburned gasses completely). Open Boiler Damper (HNA01AA001) to HRSG Completely. Exchange volume (*) of exhaust gas duct (The start up device must be suitable to perform the purging followed by a start up). Boiler is purged completely. Diverter damper (HNA01AA001) close to intermittent position.

Hot Purge (GT Natural Gas Fired Only)

Startup of GT via Bypass stack. Establish GT at low load with exhaust gas temperature after turbine and before boiler < 340°C. Open Boiler Damper (HNA01AA001) completely (100% flow via boiler). Exchange volume (*) of exhaust gas duct. Boiler is purged completely. Diverter damper (HNA01AA001) close to intermittent position.

Note (*): The purge/exchange volume of boiler is 8 volume of HRSG enclosure according to the section 5.11.5 in NFPA 85 standard. The boiler needs to be purged again if: the GT is off during purging or the Boiler damper is closed during purging the duct burner trip or failure to light off duct burners successfully shall require a repurge prior to attempting a relight 2.2.2

Proper GT Load for Lead HRSG Start After the completion of HRSG purge, the GT load shall be adjusted to maintain the following proper GT exhaust gas temperature for HRSG cold/warm/hot start.

For HRSG at the hot startup condition : HP drum metal temperature (HAD30CT102/103) + HP final superheater metal temperature (HAH33CT103~108)) ×0.62 (but, in order to avoid unnecessary cooling of HRSG, to be more than 400℃)

PAGE 7


Rev. :

B


For HRSG at the warm startup condition : less than 400℃ For HRSG at the cold startup condition : less than 400℃

In above, the HRSG cold/warm/hot startup condition is defined as follows;

Hot startup condition : HP drum pressure (HAD30CP102/103) more than 50 bara Warm startup condition : HP drum pressure (HAD30CP102/103) at 30-50 bara Cold startup condition : HP drum pressure (HAD30CP102/103) less than 30 bara

The initial GT load for HRSG start shall be fixed until the HRSG warmup is completed according to the following criteria.

HRSG HP S/H outlet steam flow (LBA30CF101/102) > 20% of Max. HP steam flow (67.07 kg/s) of one HRSG HP S/H outlet steam temp. (LBA30CT101~103) + 40℃ > GT exhaust gas temp. (HBK01CT101)

2.2.3

Diverter damper operation When the Lead gas turbine is synchronized and maintains at the proper load for HRSG start, the Lead HRSG diverter damper is opened to a partial position. Then the gas turbine exhaust gas will flow to the HRSG, for the first time. The requirements for admitting GT exhaust gas to the HRSG during HRSG cold/warm/hot start-up are as follow; For HRSG cold/warm start Divert Damper to be opened with 25 % flow(angle : about 45 deg) for 10 min. Divert Damper to be opened with 50 % flow(angle : about 25 deg) for 10 min. Divert Damper to be opened with 75 % flow(angle : about 13 deg) for 10 min. Divert Damper to be opened fully and GT Load is released to be increased after total of 30 min. in line with the ST requirements on HP steam temp., considering the capacity of HP steam attemperation. For HRSG hot start Divert Damper to be opened with 25 % flow(angle : about 45 deg) for 10 min. Divert Damper to be opened with 75 % flow(angle : about 13 deg) for 10 min. Divert Damper to be opened fully and GT Load is released to be increased after total of 20 min. Note : Diverter damper must be controlled between 10-80 degree to avoid vibration. Doosan recommends diverter damper no to be operated over 2 hours at one position.

PAGE 8


Rev. :

B


And also the ramp rate for pressure and temperature must be monitored. If the actual ramp rates exceed the predetermined value in the following table, the diverter damper opening shall be adjusted to avoid the thermal shock in HRSG tubes, drums and piping.

Cold & Warm Startup Hot Startup

HP Drum Press. (bar/min.) 1.5 3

HP Drum Metal Temp. (K/min.) 3-4 6-8

HP S/H Metal Temp. (K/min.) 5-7 12-15

Note : Opening the sequence of diverter damper will be finalized after receiving the GT startup curves showing the GT exhaust gas temperature and flow rate etc. 2.2.4

HP and LP steam isolation valve operation When the diverter damper is first opened to HRSG, HP and LP steam isolation valves (LBA30AA053 and LBB20AA054) are fully open for prewarming of the steam piping. And then, these isolation valves are always open during startup & normal operation, if there are no signal for the trip of HRSG.

2.2.5

HRSG SH Vent The start-up vent valves on the HRSGs HP/LP drum & FW tank are vented, if their respective drum or tank pressure is less than 4 bara / 2 bara & 1.5 bara respectively as follows:

2.2.6

The HP SH start-up vent valve (LBA30AA051) is fully open, when the HP drum pressure is less than 4 bara. After the pressure reaches at 4 bara, the valve is fully closed. The open of this valve shall be not permitted at the pressure more than 4 bara. The LP SH start-up vent valve (LBA30AA052) is fully open, when the LP drum pressure is less than 2 bara. After the pressure reaches at 2 bara, the valve is fully closed. The open of this valve shall be not permitted at the pressure more than 2 bara. The deaerator start-up vent valve (HAD80AA051) is fully open, when the FW tank pressure is less than 1.5 bara. After the pressure reaches at 1.5 bara, the valve is fully closed. The open of this valve shall be not permitted at the pressure more than 1.5 bara.

HRSG SH Drain, HP SH desuperheater Drain and Steam line Drain The HRSG HP and LP SH drain valves (LBA30AA052, HAH32AA051, HAH33AA051 and LBB20AA053) are open with the cyclic drain sequence (Duration time : Each 2 min. at full open position and at full closed position), if their drum pressure is less than 10 bara and 4 bara respectively. And then, if the drum pressure reaches at these set points for startup, the drain cycle will be automatically transferred to the control mode in normal operation.

PAGE 9


Rev. :

B


The drain valves upstream/downstream of HP SH desuperheater (HAH32AA051/HAH33AA051) are open with the cyclic drain sequence (Duration time : Each 2 min. at full open position and at full closed position), if HP drum pressure is less than 10 bara. And then, if the drum pressure reaches at this set point for startup, the drain cycle will be automatically transferred to the control mode in normal operation. The HRSGs HP and LP steam line drain valves (ALCB70AA051, ALCB80AA051) are open if their drum pressure is less than 15 bara and 4 bara respectively. And then, if the drum pressure reaches at these set points for startup, the drain cycle will be automatically transferred to the control mode in normal operation.

2.2.7

HRSG HP & LP Drum CBD/IBD Drain During HRSG startup, the intermittent blowdown drain valve (HAD40AA051, HAD60AA051) is to be operated in order to stabilize the HP/LP drum level at the startup level compensated by pressure. During normal operation, the intermittent blowdown drain valve is automatically open at the drum level High and is closed at normal water level. And the valve shall be open/closed by operator based on the preset water quality of drum water. The continuous blowdown valves (HAD35AA051, HAD55AA052) for the HP and LP drums will be always open. The FW storage tank does not have a continuous blowdown valve. So, the deaerator evaporator drain valve (HAD90AA051) acts as a continuous blowdown for the FW storage tank.

2.2.8

ST HP/LP Inlet Warmup Operation When HP steam flow & ST HP inlet pressure/temperature is within the certain range specified in below table, the warmup of ST shall be permitted. Hot Start Warm Start Cold Start Amb. Start 8 hr 48 hr 60 hr (150℃) 72 hr (50℃) THP Min. 430 380 360 360 Opt. 475 440 400 380 (℃) Max. 520 500 440 400 PHP Min. Not Limited Not Limited Not Limited Not Limited (Bara) Opt. Floor Press. (*) Floor Press. (*) Floor Press. (*) Floor Press. (*) Max. 90 90 90 80 One HRSG HP 20-30 20-30 20-30 20-30 Steam Flow (% of Max. Mass Flow) (*) The floor pressure at ST HP inlet : 55 bara for Yazd & Kazeroon Old sites, 72 bara for Other sites

PAGE 10


Rev. :

B


Also when the seal steam system for ST is in service and the condenser is in vacuum with the operation of hogging steam-jet ejector, the ST HP/LP inlet isolation valves can be open and the warmup of ST will be started. 2.2.9

HP Bypass Steam System Operation During HRSG startup, the HP bypass steam system will be operated as the following sequence; z HP Bypass steam system is ready for start up z The pressure set point for the HP bypass control is set to the maximum of “actual value before HRSG start up + 2 bar” and “a minimum value of 8 bara”. z When start-up pressure set point is reached, the bypass station opens to keep the pressure constant. z The bypass station stops to open when the start-up position (60%) is reached. z The pressure increases at a fixed valve position (start-up position) with the increasing steam mass flow. If the pressure increases too slowly, the start up position must be adjusted at a lower set point. If the pressure increases too fast, the start up position set-point must be adjusted at a higher set point or the gas turbine must be ramped up more slowly. z The pressure set-point for bypass valve is switched to unit set-point when ST HP inlet pressure reach at the unit set-point (floor pressure) z When the HRSG start-up is considered as completed according to the following criteria, the pressure set-point for bypass valve is set to “actual value at ST HP inlet” + “allowance for over-pressure”. The allowance for over-pressure shall be informed to operator by the ST supplier. Criteria for judging of HRSG startup complete

GT load > 50% AND HRSG diverter damper full open AND HRSG HP/LP steam isolation MOV open AND ST load > 20 MW HP steam bypass valve closed

In case of any mal-function of the boiler during start up, the bypass station will close automatically to keep the pressure in the boiler constant. Note : The contents related to turbine bypass system shall be finalized as per overall plant control concept including turbine bypass control system etc.

PAGE 11


Rev. :

B


2.2.10

GT Load Increase The GT load increase shall be followed by the operating sequence specified below;

Before HRSG purge, control the speed or load of GT to meet the GT exhaust gas temperature required for purge Before HRSG start, increase the GT load to meet the GT exhaust gas temperature required for HRSG cold/warm/hot start After HRSG warm complete, increase the GT load to meet the HP steam condition required for ST warmup start After ST warmup, acceleration & synchronisation, increase the GT load according to the unit load control philosophy, not exceeding the HRSG pressure/temperature ramp rate & ST loading instructions.

Note : The contents related to GT loading shall be finalized as per overall plant control concept including GT control system etc. 2.2.11

Duct Burner Load Increase The Duct Burner load increase shall be followed by the operating sequence specified below;

When GT load > 80% of MCR (Maximum Continuous Rating), the start of duct burner shall be permitted for the protection of HRSG. When GT load > 90% of MCR, the duct burner will be started automatically or by the operator and the duct burner will be maintained at the minimum load. In this case, the GT automatically will reduce load when ST load is increasing because of the additional steam production. When GT load reaches at 100% of MCR, the duct burner can be selected for unit load control. In this case, a PI-controller will adjust the duct burner load to match the required load target. The duct burner can be selected for unit load control individually. Duct burner load control will be very slow compared to unit control by gas turbines. Because of this, the MW ramp rate of unit control will be limited for duct burner control. To speed up the control a little bit in case of a load target change, a feed-forward signal will be implemented. Either the duct burners or the gas turbine can be selected for unit control.

Duct burner load shall be restricted by the maximum HP steam flow (67.07 kg/s) for each HRSG.

PAGE 12


Rev. :

B


2.3

Lag HRSG Start-up

2.3.1

Lag GT to Start The timing of the Lag GT to start is normally 30 seconds after the Lead GT starts, but may be coordinated such that steam is being generated in the Lag HRSG just before being needed to continue loading of the ST. The coordinated approach is the most fuel efficient approach but requires prediction of the starting and loading time of the Lead GT unit to start as well as starting and pressurization time of the Lag HRSG start. Startup of the Lag GT proceeds in the same manner as described for the Lead GT to start. Temperature matching however is now to a hot steam turbine. Loading is done at the normal GT loading rate. Note : The contents related to GT start and loading shall be finalized as per overall plant control concept including GT control system etc.

2.3.2

Purge of Boiler This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start.

2.3.3

Proper GT Load for Lead HRSG Start This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start.

2.3.4

Diverter damper operation This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start.

2.3.5

HP and LP steam isolation valve operation Before the start of lag HRSG, the HP/LP steam isolation valve shall be closed. When the following conditions are satisfied, open the lag HRSG HP/LP steam isolation MOVs for the tie-in with Lead HRSG.

2.3.6

Lag HRSG HP S/H outlet steam temp. (LBA30CT101~103) + 50℃ > ST HP inlet steam temp. Lag HRSG HP S/H outlet steam press. (LBA30CP101/102) - 3 bar > ST HP inlet steam press. Lag HRSG LP S/H outlet steam temp. (LBB20CT101/102) + 30℃ > ST LP inlet steam temp. (LBB20CP101/102) Lag HRSG LP S/H outlet steam press. - 1.5 bar > ST LP inlet steam press.

HRSG SH Vent This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start.

PAGE 13


Rev. :

B


2.3.7

HRSG SH Drain, HP SH desuperheater Drain and Steam line Drain This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start. But, common HP/LP steam line drain upstream of the HRSG steam isolation valves is not necessary for the lag HRSG start.

2.3.8

HRSG HP & LP Drum CBD/IBD Drain This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start.

2.3.9

ST HP/LP Inlet Warmup Operation Since HP and LP steam line warm-up has been already completed during Lead HRSG start-up, it is not necessary for Lag HRSG.

2.3.10

HP Bypass Steam System Operation During HRSG startup, the HP bypass steam system will be operated as the following sequence; z HP Bypass steam system is ready for start up z The pressure set point for the HP bypass control is set to the maximum of “actual value before HRSG start up + 2 bar” and “a minimum value of 8 bara”. z When start-up pressure set point is reached, the bypass station opens to keep the pressure constant. z When the start-up position (60%) is reached, the bypass station stops to open and the pressure set-point (slave) for the bypass control will track the bypass valve set-point (master) of Lead HRSG. In case of any mal-function of the boiler during start up, the bypass station will close automatically to keep the pressure in the boiler constant. Note : The contents related to turbine bypass system shall be finalized as per overall plant control concept including turbine bypass control system etc.

2.3.11

GT Load Increase The GT load increase shall be followed by the operating sequence specified below;

Before HRSG purge, control the speed or load of GT to meet the GT exhaust gas temperature required for purge Before HRSG start, increase the GT load to meet the GT exhaust gas temperature required for HRSG cold/warm/hot start

PAGE 14


Rev. :

B


After HRSG warm complete, increase the GT load so that the steam condition at the Lag HRSG S/H outlet come to the steam condition in the Lead HRSG S/H outlet. But, the GT load shall be increased within the range of the admitted HRSG pressure/temperature ramp rate.

Note : The contents related to GT loading shall be finalized as per overall plant control concept including GT control system etc. 2.3.12

Duct Burner Load Increase This part of operation for Lag HRSG to start shall proceed in the same manner as described for the lead HRSG to start.

3.0

HRSG SHUTDOWN SEQUENCE

3.1

Lead HRSG shutdown sequence For the gradual load decrease in view of the safe operation, the Lead HRSG shutdown shall be done according to the following;

3.2

Shutdown of supplementary firing (HNA10AV001) Close the diverter damper (HNA01AA001) at the rate of 10 degree/min. Close HRSG HP steam isolation MOV (LBA30AA053) Close HRSG LP steam isolation MOV (LBB20AA054) Switch HP/LP drum and FW storage tank (Deaerator) level control to single element depending on decreasing steam flow Check the diverter damper is fully closed Lock HP/LP bypass setpoint to the measured HP/LP S/H outlet pressure Close HP/LP/FW Tank Level Control Valves (HAC30AA151,152/ LAC70AA151,152/ LCB80AA151,152) after HP/LP steam bypass valve is closed continuously Close all isolation MOVs for HP/LP/FW Tank Level Control Valves (HAC30AA051,052/ LAC70AA051,052/ LCB80AA053,054)

Lag HRSG shutdown sequence For the gradual load decrease in view of the safe operation, the Lag HRSG showdown shall be done according to the following;

Shutdown of supplementary firing Close the diverter damper to intermediate position 60% (The value shall be tuned up during the commissioning period, if necessary) depending on the design capacity of HP steam bypass valve. Switch ST control to "limit press. Control" and then Shut down ST. Fully close diverter damper at the rate of 10 degree/min. Switch HP/LP drum level control to single element depending on decreasing steam flow PAGE 15


Rev. :

B


3.3

Check the diverter damper is fully closed Close HRSG HP steam isolation MOV Close HRSG LP steam isolation MOV Lock HP/LP bypass setpoint to the measured HP/LP S/H outlet pressure Close HP/LP/FW Tank LCVs (Level Control Valve) after HP/LP steam bypass valve is closed continuously Close all isolation MOVs for HP/LP/FW Tank LCVs (Level Control Valve)

HRSG trip sequence The following signals will be the source of the HRSG trip. HP drum level HH or LL LP drum level HH or LL FW tank level HH or LL Guillotine damper not open ST tripped and bypass steam system is not available GT tripped Instrument air pressure LL Two FW pumps tripped Manual emergency trip PB(Push Button) pushed HP super heater temperature high- high Diverter damper hydraulic oil pressure low- low After HRSG tripped, if diverter damper does not leave the open position after 5 seconds or does not reach to close position after 60 seconds (typical), the GT will be tripped. In above emergency condition, the HRSG shall be tripped according to the following;

Trip the supplementary firing Quick close the diverter damper to full close position Close HRSG HP steam isolation MOV Close HRSG LP steam isolation MOV Close HP/LP/FW Tank LCVs (Level Control Valve) Lock HP/LP bypass setpoint to the measured HP/LP S/H outlet pressure Close all isolation MOVs for HP/LP/FW Tank LCVs (Level Control Valve)

In the following conditions, the duct burner shall be tripped.

Duct burner outlet gas temp. > Maximum allowable temperature Further trip conditions, see the section.5.1 in the “Duct Burner Operating & Safeguarding Description”

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startup and shutdown procedure

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