HP-LP Bypass System
m e t s y S s s a p y B P L / P H
HP-LP Bypass System HP Bypass Valve HP Bypass Spray Valve LP Bypass Valve LP Bypass Spray Valve Electro Hydraulic Actuating System
HP-LP Bypass System HP-LP Bypass System
High pressure (HP) and Low pressure (LP) bypass systems are used for quick start-up of the unit as well as during trip-out, where load rejection at the turbine does not automatically lead to a boiler trip. With a bypass system, start-up is quicker. The system diverts the steam generated by the boiler to the Re-heater/Condenser, at the same time reducing the pressure and temperature of steam, thus maintaining a minimum circulation of steam through the boiler. This enables running the boiler without the turbine in service, ensuring flow through re-heater coils. BHEL HP-LP bypass system has the following advantages : The prolonged venting of safety valves to atmosphere is avoided, thereby reducing DM water loss and cutting noise emission. Contd...
HP-LP Bypass System HP-LP Bypass System
Sustained flow through the boiler heating surfaces is assured, ensuring Re-heater protection during start-up of units. If the grid cannot accept power, the unit can be kept running on house load. Almost all power plants are provided with HP-LP bypass systems for technical and economical reasons. The technology has been obtained from SULZER THERMTEC, Switzerland and we manufacture all the components in-house. BHEL has supplied bypass systems to over 150 power plants of 120/210/250/500 MW rating with a total installed capacity of over 32,000 MW.
HP-LP Bypass System HP-LP Bypass System LEGEND BP - HP BYPASS VALVE BD - SPRAY WATER ISOLATION VALVE HRH
BPE - SPRAY WATER FLOW CONTROL VALVE
MSL
LBP - LP BYPASS VALVE LPC - LP COOLER
BP
LBPE - LP BYPASS SPRAY VALVE
BOILER
HPT
LPT
MPT
HPT - HIGH PRESSURE TURBINE MPT - MEDIUM PRESSURE TURBINE
CRHNRV CRH
LPT - LOW PRESSURE TURBINE
LPC LBP
CON
CRHNRV - CRH NON RETURN VALVE BFP - BOILER FEED PUMP
BPE LBPE
CON - CONDENSER MSL - MAIN STEAM LINE
BD
HRH - HOT REHEAT LINE BFP
CRH - COLD REHEAT LINE
HP-LP Bypass System HP Bypass Valve
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Combined pressure reducing and de-superheating valve.
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Steam pressure reduction by throttling and temperature reduction by spray water injection
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To suit varying high pressure and temperature, the valve body is made from forged material of 2¼ Cr 1 Mo steel (A182 F22 Cl.3).
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To keep the stresses in optimum level, valve body is made of spherical shape.
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Leak tight seat. (HS 25)
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Stem is made from high chrome alloy steel 11 Cr 1 Mo (X19CrMoVNbN111).
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Design pressure
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Design temperature : 545°C
Model Nos: ARS 45, ARS 50, ARS 63, ARS 72, ARS 80, ARS 90, ARS 100, ARS 112, ARS 140 & ARS 140A
: 200 kg/sq.cm
HP-LP Bypass System HP Bypass Spray Valve
Model No : E22S, E32S, E45S
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For spray water flow control to HP Bypass Valve.
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Pressure reduction & flow control achieved in three stages to avoid erosion due to high pressure drop.
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Valve body is of "Z" configuration made from forged carbon steel A 105.
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Stem is made from high chrome alloy steel 11Cr 1Mo (X19CrMoVNbN111)
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Leak Tight Stellite Seat.
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Design pressure
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Design temperature : 300°C
: 350 kg/sq.cm
HP-LP Bypass System LP Bypass Valve
Model No : NR 64-500 EK
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Pressure reducing valve.
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Steam pressure reduction by throttling.
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Valve body is made from forged material of 2¼ Cr 1 Mo steel (A 182 F 22 Cl.3)
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Stem is made from High Chrome alloy steel 11Cr 1 Mo (X19CrMoVNbN111)
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To keep the stresses at optimum level, valve body is spherical in shape.
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Leak tight seat.
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Design Pressure
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Design Temperature : 540°C
: 64 kg/sq. cm
HP-LP Bypass System LP Bypass Spray Valve
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For spray water flow control to LP Bypass valve
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Valve body is made from forged Carbon steel A 105.
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Stem is made from High Chrome alloy steel 11Cr 1 Mo (X19CrMoVNbN111)
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Leak tight seat.
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Design Pressure
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Design Temperature : 300°C
: 50 kg/sq. cm
HP-LP Bypass System Electro Hydraulic Actuating System Electro hydraulic actuating system is a complete modular unit with a wide range of actuator cylinders (type ASM) having a
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force of about 100 tonnes and large stroke. 8
It consists of an Actuator cylinder (type ASM), Oil supply unit (type OV 32B), Servo valve (type ST), Blocking unit (type BL),
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Step control unit (type APL), Quick stroking device (type SSB).
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Each actuator is equipped either with one Servo valve and 1 6
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Blocking unit or a step control unit. Servo valve and blocking element control the open/close and stay-put function of the valves.
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1. Actuator cylinder, type ASM 2. Oil supply unit, type OV 32B 3. Servo valve, type ST 4. Blocking unit, type BL 5. Step control unit, type APL 6. Connection plate 7. Additional accumulator 8. Quick stroking device, type SSB
Hydraulic oil required under high pressure for the operation of the valves under high steam pressure is supplied by the Oil supply unit.
