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Presentation outline

Introduction to HPBypass

Components of HPBypass SystemSystem Details

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To improve flexible operation

Dumping of excess steam to

Bypass steam from boiler when turbine isnot in service.

To quickly match steam parameters with thatof turbine metal.

To protect reheat tubes

Minimize water loss(Sh vent to be open

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H.P. Bypass system bypassed steam from MS line to CRH linebypassing HPT.

Function of HP Bypass:-

1. Raising boiler parameter during start up.

2. To warm up steam pipe lines.3. To match live steam pressure & temp before entering into turbine.

4. Quick

5. start up of turbine.

6. Bypasses the steam to HPT & during sudden unloading of

machine, tripping of machine.7. Avoid starvation of boiler.

8. Reduce losses of steam to atmosphere.

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Working of By pass system (Explain Fig)

Maintains pressure before Turbine i/L

2 BP1,BP2 Upstream ,Down stream CRH

Dump excess steam to cold RH

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Capacity to bypass 70% HP steam at rated flow

HP ,BPE (spray ) are hydraulic actuator

Pressurized oil is supplied from separate oil Unit

Fast opening ( Bulk load ,generator Trip, Turbinetrip )

During normal operation (sliding pressure set point)

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Opening-

Generator circuit breaker open. Turbine trip out.

Manual command for fast opening.

Protection- Condenser vacuum too low.

Temp. to high at down stream of H.P. Bypass.

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Oil supply unit

Two oil pumps.

Two tanks.

Signal alarm PRESSURE TO HIGH orPRESSURE TO LOW if pressure is not in order.

02 nos. of pressure control valves

02 nos temperature control valves

01 no. of spray water pressure control valve

01 no. of spray water pressure isolating valve

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Hydraulically operated

Steam pressure control

Down steam temperature control

Spray water pressure control.

On -off control

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Oil supply units

Servo valves

Blocking units

Trip close/trip open units

Filters

Regulators.

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Hydraulic system pressure control

Pressure controls

Temperature control

Valve positioning control

Annunciations

Power supplies

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Spray water pressure auto switching

Auto opening of spray isolation valve

Trip closing of bypass valves

Trip opening of bypass valves.

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Hp bypass system

02 nos of control valves

02 nos of temperature control valves

01 no. of spray water isolation valve

Trip closes on

-down steam temperature very high

-vacuum is low

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