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heat recovery steam generator of a power plant

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  • ATION MANUAL: P.I.O.I Volume 8 Page 1 Rev 0

    INDEX

    Page No 1 Objectives 2

    2 Potential Hazards 3 3 Description 3.1 Purpose and General Description 4 3.2 Characteristics and Data 12 3.3 Control Systems 13 3.4 Alarms and Set Points 23 3.5 Auxiliary Systems 24 4 Supporting Documents 25

  • OPERATION MANUAL: P.I.O.I Volume 8 Page 2 Rev 0

    1.OBJECTIVES

    The objectives of the procedure are as follows To provide a basic level of knowledge for process shift teams to understand the layout and operate the Heat Recovery Steam Generators together with the HP, IP and LP Steam Systems.

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    2. POTENTIAL HAZARDS

    The potential hazards, which can arise from operating the steam system, are.

    Injury to personnel by accidentally touching hot equipment or steam leaks

    Hot pipework should be insulated for heat retention and personnel protection, where insulation is damaged, arrangements should be made to replace insulation and make the work area safe. Protective clothing must be worn to operate or inspect equipment, where it is not practical to fit heat shields for personnel protection. Where steam leaks are hazardous, for example Super heated steam leaks can be invisible, barriers should be erected to protect personnel in the work area and arrangements made to stop the steam leak as soon as possible.

    Fire when oil impregnated insulation reaches its auto ignition temperature. Oil impregnated insulation will auto ignite at temperatures above 400 deg F.

    Where leakage of oil can fall on hot pipework or contaminate Insulation the oil should be diverted from the pipework and the leak repaired as soon as possible. Oil contaminated lagging should be removed from the work area.

    Injury from chemicals used for treating feed water to the HRSG. Hydrazine (Injected into the condensate) Ammonia Phosphate Comment on dangers

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    3.1 PURPOSE & GENERAL DESCRIPTION

    The purpose of the steam system is to provide steam for: -

    the generation of electricity,

    the deaeration of feed water and pressure control of the deaerator, The steam system consists of three Heat Recovery Steam Generators and one Steam Turbine Generator. A Heat Recovery Steam Generator (HRSG) is an unfired boiler, generating steam in three separate pressure systems, from the heat in the exhaust gas emitted by the Gas Turbine. The three pressure systems are termed, High, Intermediate and Low pressures steam.

    High Pressure steam is utilised in the Steam Turbine Generator

    Intermediate Pressure steam is used in the Steam Turbine Generator and Deaerator.

    Low Pressure steam is used in the Deaerator The HRSG operates on natural circulation with the steam generating tubers together with superheater and economiser sections suspended vertically from the roof of the heat transfer chamber. A heat exchanger mounted at the exhaust gas outlet of the HRSG, heats condensate before it enters the deaerator. The Steam Turbine generator is a 197-megawatt machine with a condensing turbine High Pressure Steam System (HP) (Refer to the simplified drawings for the HRSG water and steam flow for HP, IP and LP steam systems) Feed water to the HP steam drum is supplied from the feed pump discharge header through a control set of feed regulating valves and an economiser. The economiser is in four separate sections, with manually operated drain valves on each section, together with flue temperature measurement at the inlet and outlet of the Economiser. The control set of feed regulating valves consists of two control valves in parallel and a manual bypass valve. One control valve is used for start-up the other for normal operation. The feed regulating valves are operated by the steam drum level control system, which comprises a three element and single element control scheme, The three-element control is used for normal operation, while the single element is used for start-up.

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    3.1 PURPOSE & GENERAL DESCRIPTION

    Boiler Blow Down

    Intermittent blow down is available from the generating tube header through manually operated valves, the boiler manufacture recommends use of intermittent blow down when the concentration of total dissolved solids exceeds the required specification.

    Continuous blow down from the steam drum during normal operation, is available through actuator operated valves controlled through DCS.

    The steam drum has the following equipment, Safety Relief valves, Water level Gauge for local indication, Hydrastep ( for remote drum level measurement) Three analogue level transmitters, (for drum level control) Two analogue pressure transmitters, One local pressure gauge, Chemical dosing line, Continuous blowdown system, Nitrogen connection (for dry storage of HRSG) Measurement of drum metal temperature The feed water leaves the drum through down-commers (pipework) which supply the header at the bottom of the generating tubes, the water rises through the generating tubes where its heated and some of it is changed into saturated steam. (steam water mixture) The steam water mixture re-enters the drum through a cyclone separator, which removes droplets of water from the steam. The steam then leaves the drum and enters the superheater section. The superheater consists of six banks of tubes on the gas inlet side of the HRSG. The superheater headers have drain valves operated automatically through DCS There is no control over the superheater outlet steam temperature, it is allowed to vary with the gas flow and temperature of the Gas Turbine exhaust gasses.

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    3.1 PURPOSE & GENERAL DESCRIPTION

    The HP steam line from the HRSG is equipped with: Flow measurement, with correction for temperature and pressure. Safety relief valve, Stop and non-return valve, Manual shutoff valve Motorised shutoff valve, with manual and actuator operated bypass valve Temperature and Pressure indication Actuator operated start-up vent to atmosphere, through a silencer. Steam Bypass control system When the HRSG exceeds its safe operating pressure, the safety valve on the superheater will operate first, This ensures a flow of steam through the superheater and prevents excessive metal temperatures, which could damage the tubes. If the pressure continues to rise, the safety valves on the steam drum will operate. The HP steam outlets from the three HRSGs are connected to a header, which supplies the Steam Turbine combined control and stop valve. The HP steam enters the first stage of the steam turbine and expands through the turbine, to the condenser. Condensate is automatically removed from the steam mains by actuator operated drain valves, controlled through the Distributed Control system (DCS) The actuator operated drain valves can also be operated through a control scheme in DCS, to warm through the steam mains during start-up. HP Steam Bypass The steam bypass provides the facility for HRSG start up by passing the steam generated to the condenser of the steam turbine and also allows the HRSG to continue operation in the event of the Steam Turbine shutting down. A connection on the HP steam outlet from the HRSG provides a Bypass around the boiler stop valve and steam header, to supply steam through a pressure reducing valve and desuperheater to the Turbine Condenser. The Steam Turbine Condenser has the capacity to condense the full load steam flow from three HRSGs.

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    3.1 PURPOSE & GENERAL DESCRIPTION

    Steam Bypass Control Valve The Steam By-Pass pressure reducing and desuperheating stages are controlled through the D.C.S . The actuator on the Steam Bypass Control Valve is operated by hydraulic oil supplied from a pumping unit, while the desuperheater spray water control valve has an air operated actuator. Hydraulic power oil for the actuator is provided by motor driven pumps with an off line oil filtration circuit. The pumps produce a discharge pressure between 140 and 180 bara, which then passes through a pressure reducing valve to provide a control oil pressure of 100 bara. Two accumulators are fitted in the oil circuit to too minimise the effect of pressure fluctuations, on the control valve actuators, The actuators are double acting, with a proportional valve for modulating control and a solenoid valve for trip closure, together with a valve position indicator and an oil filter to protect the actuator operating mechanism.

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    3.1 PURPOSE & GENERAL DESCRIPTION

    Intermediate Pressure Steam System (Refer to the simplified drawings for the HRSG water / steam flow together with HP, IP and LP steam flow Feed water to the Intermediate Pressure steam drum is supplied through an Economiser and control valve from an intermediate pressure header. The header is pressurised from a tapping point located on the low-pressure section of the feed water pump. The feed water flow to the IP steam drum is controlled by a single control valve and preheated in a single economiser section before entering the steam drum. The economiser has manually operated drain valves. The feed regulating valve is operated by the steam drum level control system, which comprises of a three element and single element control scheme, Three Element control is used for normal operation, while the Single Element is used for start-up. Boiler Blowdown

    Intermittent blow down is available from the generating tube header during startup. through manually operated valves.

    Continuous blown from the steam drum during normal operation, is available through actuator operated valves.

    The steam drum has the following equipment, Two Safety Relief valves, Water level Gauge for local indication, Hydrastep for remote drum level measurement Three analog level transmitters, for drum level control Two analog pressure transmitters, One local pressure gauge, Chemical dosing line, Continuous blowdown system, Nitrogen connection (for dry storage of the HRSG)

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    3.1 PURPOSE & GENERAL DESCRIPTION

    The feed water leaves the drum through downcommers (pipework) which supply the header at the bottom of the generating tubes, the water rises through the generating tubes where its heated and changed into saturated steam. (steam water mixture) The saturated steam re-enters the drum through a separator, which removes droplets of water from the steam. The wet steam then leaves the drum and enters the superheater section. The superheater consists of one bank of tubes, there is no control over the steam outlet temperature, it is allowed to vary with the gas flow and temperature of the exhaust gases from the Gas Turbine The superheater header has actuator-operated drain valves controlled through the DCS. The IP steam line from the HRSG is equipped with Flow measurement, Safety relief valve, Stop and non-return valve, Manual shutoff valve and motorised shutoff valve, Temperature and pressure measurement Actuator operated start-up vent valve to atmosphere. Actuator operated drain valves. Steam Bypass control system The safety valve on the Superheater is set to operate at a lower pressure than the Steam Drum Safety valves. The IP steam outlets from the three HRSGs are connected to an IP steam header, which supplies

    The Steam Turbine Generator at a low pressure stage in the Turbine.

    Provides steam to the deaerator when there is not enough LP steam

    Steam to the turbine glands during start up and low load operation. The IP steam enters the Steam Turbine casing through an actuator operated emergency stop valve and control valve. IP Steam Bypass A connection on the IP steam outlet from the HRSG provides a Bypass around the boiler stop valve and steam header, to supply steam through a pressure reducing valve and desuperheater to the Turbine Condenser.

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    3.1 PURPOSE & GENERAL DESCRIPTION

    Low Pressure Steam System (Refer to the simplified drawings for the HRSG water / steam flow together with HP, IP and LP steam flow Feed water to the Low Pressure steam drum is supplied through a control valve from the intermediate pressure header. The header is supplied from a tapping point located on the low-pressure section of the feed water pump. The feed regulating valve is operated by the steam drum level control system, which comprises of a three element and single element control scheme, Three Element control is used for normal operation, while the Single Element is used for start-up. Boiler Blowdown

    Intermittent blow down is available from the generating tube header through manually operated valves.

    Continuous blown from the steam drum during normal operation, is available through actuator operated valves.

    The steam drum has the following equipment, Two Safety Relief valves, Water level Gauge for local indication, Hydrastep for remote drum level measurement and tripping, Three analog level transmitters, for drum level control Two analog pressure transmitters, One local pressure gauge, Chemical dosing line, Continuous blowdown system, Nitrogen connection.

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    3.1 PURPOSE & GENERAL DESCRIPTION

    The feed water leaves the drum through downcommers (pipe work) which supply the header at the bottom of the generating tubes, the water rises through the generating tubes where its heated and changed into saturated steam (wet steam). The saturated steam re-enters the drum through a separator, which removes droplets of water from the steam. The steam leaves the drum and enters the Low Pressure steam header Steam from the LP header is distributed to the Deaerator and in the event of a high pressure in the LP header, through a control valve to the steam turbine condenser. The LP steam line from the HRSG is equipped with Flow measurement, Safety relief valve, Stop and non-return valve, Manual shutoff valve and motorised shutoff valve, Temperature and pressure measurement Actuator operated start up vent valve to atmosphere. Actuator operated drain valves. HRSG Gas Outlet Economiser The Economiser on the gas outlet of the HRSG transfers heat to condensate prior to the condensate entering the Deaerator. Condensate heating is not available while the Gas Turbine burns Diesel Fuel oil, due to the Sulphur content in diesel producing Sulphurous Acid in the exhaust gases. which will produce corrosion of the economiser tubes. A control scheme in DCS operates the position of two control valves to either pass the flow of condensate through the economiser or bypass the economiser and transfer the condensate directly to the Deaerator.

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    3.2 CHARACTERISTICS & DATA SHEET

    ITEM SET-POINT HRSG (HP) Safety Valves Operating Pressure Steam Drum 1 103 bar 2 ? bar Superheater 100 bar

    Feed Water pressure 12124 bar

    Feed Water Inlet Temperature 1192 OC Economiser Outlet temperature Steam Drum Pressure Superheater Outlet Temperature 507 0C

    Superheater Outlet Pressure 895 bar Steam Flow 185 Tonnes/hr HRSG (IP) Safety Valves Operating Pressure Steam Drum 1 ?bar

    2 ?bar Superheater ?bar Feed Water Pressure 22 bar Feed Water Inlet Temperature 115 OC Economiser Outlet temperature Steam Drum Pressure Superheater Outlet Temperature 264 OC

    Superheater Outlet Pressure 703 bar

    Steam Flow 5096 Tonnes/hr? HRSG (LP) Safety Valves Operating Pressures Steam Drum 1 bar 2 bar Feed Water Inlet Temperature 115 OC Steam Drum Pressure 5.4 bar Outlet Temperature 129 OC Steam Flow 5.39 Tonnes/hr Low Temperature Economiser Outlet Temperature 160OC

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    3.3 CONTROL SYSTEMS

    Steam Drum Level Three Element Control This control system is the same for each of the HP,IP and LP drums The position of the feed water regulating valve is controlled by a three element control system, which utilises steam flow compensated for changes in pressure and temperature, together with feed water flow measurement and steam drum level measurement. Steam drum level, is measured by three level transmitters and the average signal is pressure compensated for changes in water density, over the operating range of the HRSG. The control system can be used in single element or three element control mode

    FT 001

    A

    HP

    FT 011

    A

    CP CP CP

    BF

    LT-011

    A-1

    BF

    LT-011

    A-3

    BF

    LT-011

    A-2

    BF

    LC-011

    A

    LV-001

    A

    PT-002

    A-1

    PT-002

    A-2

    STEAM

    OUTLET

    B.F.W. INLET

    (H.P.)

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    3.3 CONTROL SYSTEMS

    Single Element Control Single element control is normally used during start up of the HRSG when steam flow is not measured or when steam flow is low and water flow is erratic. It can also be used during normal operating conditions if either the steam or water flow elements are out of service for maintenance. Single element can only respond to changes in drum level after the change has taken place, but it is still an effective form of level control. DCS will automatically select single element control when the steam flow is below 56Tonnes/hr and if the feed water or steam flow measurement fail during normal operation. Three Element Control The three elements are: - Drum Level - Water Flow In. - Steam Flow Out During normal operation the three elements are constantly monitored by LT-011-A/B/C,(Drum Level) FT-001A (BFW inlet) and FT 011A(Steam flow outlet) An input signal is sent from each of these monitors to the controller LC-011A, which compares the input signals with its set point. Based on this LC-011A sends a signal to the boiler feedwater control valve LV-001A, which will open or closed depending on the signal received and maintain the drum level at the required set point. During normal operation the HRSG steam generation will always be changing. Which will require a change in feed water flow to maintain the water level in the drum and prevent a low drum water level, which could lead to a low-level trip. Or, high level, which could cause carry over of water into the superheater section, which, could result in damage to the steam turbine. When the drum level has been restored to its normal working level and steam flow equals the feed water, the three element control system will be in balance, for a new opening on the feed water control valve.

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    3.3 CONTROL SYSTEMS

    Steam Drum Level Control Philosophy

    To control the water level at the set point value during start-p and normal operation. Trip Function;

    To prevent high water level, which could carry over to the superheater and enter the steam turbine.

    To prevent low drum level which could lead to a shut down of the HRSG HRSG Automatic Operation of HP,IP and LP Drum Level Control During Startup HP DRUM After the synchronising operation is completed during a Gas Turbine start up, electrical generation is immediately increased from zero to 20 MWs, this results in high heat transfer to the water in the HRSG over a short period of time, causing expansion of the water and a rapid increase in drum level. The objective during start-up is to prevent high drum level through automatic control, using the following schemes.

    If the feed water control valve is less than 3% open for 5min the motorised feed water shut off valve will close and reopen when the control signal has reached 5%.

    DCS will automatically select single element control when the steam flow is below 56 Tonnes/hr

    Automatic Drum Level lowering

    Automatic drum level lowering is controlled through DCS during start up.

    The control system utilises the motorised valves on the continuous and intermittent blow down valves, to drain water from the HRSG.

    Prior to start-up the steam drum should be filled to -150 mm.(normal working level is 0mm)

    At start-up the feed regulating valve is automatically given a set point value of less than 150 (which means the feed regulating valve will be closed)

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    3.3 CONTROL SYSTEMS

    On the startup sequence the control scheme checks the following

    - Motorised drain valves closed.

    - Two minutes circulation through the generating tubes (2 minutes circulation ensures that any change in drum water level will have passed) HOW IS THIS MEASURED? After 2 minutes circulation, the automatic drum level lowering is enabled.

    A set point of 150 mm is given to the drain control valves,

    If the drum level increases the drain valves will open.

    If the drum level falls the feed regulating valve will open.

    Automatic drum level lowering is disabled when the following conditions exist - The HP steam flow exceeds 36 Tonnes/hr for two minutes. - The HP pressure exceeds 24 barg - With the Drum level at 0mm or lower. At this point DCS automatically changes - The Drum level lowering set point to +250 mm - The HP feed water regulating set point to 0mm The control philosophy for IP and LP Drum Level lowering is similar to the HP Drum. Except for: - IP and LP Drum level lowering is available throughout the working range of the HRSG - The initial setpoint given to the drain valves after 2 minutes circulation is -200 mm. - This setpoint is changed to + 200 mm when the IP and LP steam flow has been higher than 15 Tonnes /hr for more than 2 minutes. HP. IP. and LP Automatic Operation of Motorised Vent Valves During the HRSG start up and shutdown sequence the motorised vent valves on the Steam Drum and superheater outlet are automatically operated by DCS. On start up both HP Drum and Superheater outlet vents are closed automatically by DCS.

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    3.3 CONTROL SYSTEMS

    When the pressure exceeds 1.25 bar and the temperature in the Downcommer exceeds 120 deg C. (clarify) no temperature measurement on P& IDs On shut down the HP Drum and Superheater outlet vents are automatically opened when the HP pressure reduces below 0.75 bar, too prevent a vacuum forming during cool down. On start up the IP and LP vents are automatically closed when the Low Pressure Drum exceeds 1.25 bar. On shut down the IP and LP vents are automatically opened when the IP and LP pressure falls below 0.75 bar. HP. IP and LP Steam Mains Automatic Warming During pressure raising on the HRSG, the DCS automatically operates the motorised drain valves on the Steam Mains to warm through and free the system of condensate.

    HP Steam Main The warm through sequence is automatically started and the drain valves opened, when the HP drum pressure is greater than 2 bar. The drain valves are automatically closed when the steam flow exceeds 40 Tonnes/hr. ? D.C.S then switches the drain valves to automatic temperature control. Automatic operation is not available during shut down of HRSG

    IP and LP Steam Mains The warm through sequence is automatically started and the drain valves opened, when the IP and LP drum pressure is greater than 1 bar. The drain valves are automatically closed when the IP steam flow exceeds 30 Tonnes/hr.

    (clarify high steam flow ) D.C.S then switches the drain valves to automatic temperature control. Automatic operation is not available during shut down of HRSG

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    3.3 CONTROL SYSTEMS

    Steam Bypass Control Valves Before the Steam Bypass control system can operate, the following list of permissives must be satisfied.

    Steam Turbine condenser pressure No 1 less than < 0.2 bara

    Steam Turbine condenser pressure No 2 less than < 0.2 bara

    Vacuum breaker closed

    Steam Turbine gland sealing steam ON. Gland steam sealing pressure greater than > 0.04 bara

    Steam Turbine gland sealing steam exhauster fans ON Air extraction system ON HP/IP Steam Bypass hydraulic oil supply unit ON HP/IP Steam Bypass hydraulic oil supply unit fault not initiated HP/IP Steam Bypass hydraulic oil supply unit NOT tripped

    HP/IP Steam Bypass isolating valves Open clarify not shown on P& IDs The Steam Bypass control valve will close automatically under any of the following conditions. Spray water pressure less than 4barg Spray water control valves fails to open within 5 seconds of the associated steam pressure reducing control valve opening. Steam temperature at LP stage in the Steam Turbine condenser greater than 120deg C. High level in the Hot Well. Condenser pressure high 500mbar a. Loss of hydraulic oil supply. Loss of electrical power supply to control equipment.

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    3.3 CONTROL SYSTEMS

    The Steam Bypass operates on automatic control for the following conditions:

    Start up and independent operation of the Gas Turbine and HRSG, up to maximum continuous rating.

    Start up Steam Turbine

    To ensure stable operation of HRSG and Gas Turbine, in the event of a change in load on the Steam Turbine due to a trip or load rejection.

    Start up of a HRSG. The control scheme initiates the following sequence of events for the HP Steam Bypass during start up of a HRSG

    The Steam Bypass pressure control valve is selected to warm up mode, to prevent thermal shock.

    The control system uses thermocouples to check the temperature differential between the metal of the control valve and steam. If the differential is greater than

    150 OC the control scheme opens the drain valve HP-AOV 028. (clarify)

    When the differential is less than 150 OC the drain valve is automatically closed and the control scheme selects auto on, the Steam Bypass pressure controller HP-PC 030 and the desuperheater temperature controller HP-TC 030 to put the bypass in service.

    The control scheme then selects the setpoint for pressure and temperature controllers, together with ramp rates to control the rate of rise in the steam outlet pressures of the HRSG, from start-up to normal working pressure.

    Pressure controller HP-PC 030 operates the HP Steam Bypass pressure-reducing valve HP-PV 030.

    HP-PC 030 receives a process variable control signal, from the HRSG steam outlet pressure transmitter HP-PT 011, with a pressure feed back signal from PT 030

    Together with an override pressure signal from CD-PC001 the Condenser Pressure Controller. Which closes the HP Steam Bypass pressure control valve in the event of the Condenser pressurising.

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    3.3 CONTROL SYSTEMS

    The HP setpoint is selected to the maximum normal working pressure of 89 barg. While the rate of rise in pressure, is controlled by the ramp rate, which can be set at 2 barg per minute. Note: The ramp rate is limited by the recommended rate of rise in Steam Drum metal temperature, of 9 OC per minute. Measured by two surface mounted thermocouples BF-TE 012 (1&2) The HP desuperheater set point on HP-TC 030 is set to control at a temperature of 32 OC. IP Bypass: The Steam Bypass pressure control valve is selected to warm up mode, to prevent thermal shock. The control system uses thermocouples to check the temperature differential between the metal of the control valve and steam. If the differential is greater than 150 OC the control scheme opens the drain valve HP-AOV 038. (clarify) When the differential is less than (

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    3.3 CONTROL SYSTEMS

    The IP setpoint is selected to the maximum normal working pressure of 5.0 barg. While the rate of rise in pressure is controlled by the ramp rate which can be set at 2 barg per minute. Note: The ramp rate is limited by the recommended rate of rise in Steam Drum metal temperature, of 9 OC per minute???. Measured by two surface mounted thermocouples BF-TE 022 (1&2) The IP desuperheater set point on HP-TC 030 is set to control at a temperature of 32 OC.

    IP

    TE-038

    A

    IP

    PT-040

    A

    IP

    TE-042

    A

    IP

    PC-040

    A

    FROM IP HEADER PT FROM CONDENSER VACUUM

    PTS (CO-PC-001)

    IP

    TC-040

    A

    TO

    CONDENSER

    FROM IP STEAM

    HEADER

    IP

    HS-038

    A

    TO

    BLOWDOWN

    TANK

    FROM

    B.F.W.

    DISCHARGE

    FC

    FO

    FC

    IP

    PV-040

    IP

    AOV

    038

    BF

    TV-040

    IP

    DS-040

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    3.3 CONTROL SYSTEMS

    Automatic Control of LP steam to Steam Turbine Condenser LP steam is normally used in the Deaerator, but in the event of Low Pressure Steam exceeding the working pressure. Control valve PV 009 will open and allow LP steam to pass to the condenser, with no requirement for reduction in temperature. Control valve PV 009 is operated through pressure controller PC 009, which receives a control signal from pressure transmitter PT 009 and an override signal from PC 001 which monitors the condenser pressure. If the condenser starts to pressurise the override signal from PC 001 will change the output of PC 009 to close PV 009 and reduce the LP steam to the condenser.

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    3.4 ALARMS & SET-POINTS

    Alarm Tag No Description Process Value HRSG HP Steam Drum High Level Alarm +200mm HP Steam Drum Low Level Alarm -100mm HP Steam Drum High Level Trip +450mm HP Steam Drum Low Level Trip - 700mm HP Steam Drum pressure High HP Steam Outlet pressure High IP Steam Drum High Level Trip IP Steam Drum Low Level Trip LP Steam Drum High Level Trip +350mm LP Steam Drum Low Level Trip -450mm

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    3.5 AUXILIARY SYSTEMS

    HRSG Blowdown Tank The Blowdown tank is an atmospheric vessel, which receives drains from the following points on the HRSG and steam mains.

    HP drains header.

    IP drains header.

    LP drains header.

    HRSG HP,IP and LP continuous blowdown.

    HRSG HP,IP and LP intermittent blowdown. Service water is sprayed into the tank, to condense the flash steam generated by the high temperature water from the drain systems. Water drains from the tank and passes through an inverted U loop to the waste water recovery basin. The height of the inverted U loop controls the working level of water in the blow down Drum. The flow of Service Water to the Blowdown Tank is determined by a control loop, which comprises of: A temperature sensor TE007, which monitors the water outlet temperature value from the Blow down Tank and provides a control signal for temperature controller TC007, which adjusts the position of the Service Water flow control valve TCV007. Steam that is not condensed is allowed to vent to atmosphere.

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    4 SUPPORTING DOCUMENTS

    This manual is supported by: Vendor Manual P.I.O.I,s (Plant Item Operating Instructions). Sections 8.1,8.2,and 8.3 P & I Drawings M-MD1601 M-MD1602 MD0501