VHB Presentation [Compatibility Mode].pdf

7/26/2019 VHB Presentation [Compatibility Mode].pdf

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FEEDWATER HEATER BYPASSSYSTEMS

Feed Heater Bypass

SystemVHB


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2002. CCI Control Components Inc. All rights reserved.

VHB2 & VHB 3

Protects the feedwater heatersteam jacket in case of tuberupture or leakage.

Protects the turbine extractionfrom excessive backpressure.Or water carry over

Allows the feedwater heater tobe isolated from the system

without disrupting thecirculation through the plant.

Allows bypassing of thefeedwater heater during plantstart-up at low turbine load.

Allows bypassing of thefeedwater heater at peak loadsto increase output from theturbine.


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Boiler feedwater heater bypass System Existing / Proposed

Existing Proposed


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VFA-HP

Steam to turbine / process

BoilerFeedwater

Feedwater heater bypassed Feedwater heater operation

From turbineextraction

To condensatesystem

Feedwater Heater Bypass Valve


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Under normal conditions

the feed heater is on-line, the bypasspiping is fil led with pressurized water, butis shut down on its upstream side.

Resetting the system to normalconditions, i.e. passing the fluid againthrough the feed heater, is usually doneslowly and carefully by local manualactions but can also be done remotely.


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Feedwater Heater Bypass Valve VHB-3

Valve in bypass position


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Feedwater Heater Bypass Valve VHB-2

Valve in bypass position


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Actuating system

Actuation is typically within 5 second

Three actuating systems are possible:

1 Hydraulic, using the feedwater as fluid (Noexternal power source is required)

2 Pneumatic, using standard piston actuators

3 Electric, Limited operating speed, Thestandard electric actuator is AUMA but otherscan be selected on request. System control tobe included in DCS. No safe failure action!!!


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VHB-T3WH

VHB with water hydraulic in normal mode


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VHB-T3WH

VHB 3, Self acting HydraulicsNormal to Bypass Mode

The upper chamber is pressurizedthrough the valve A.

The on/off valve B opens and evacuatesthe pressure in the lower chamber of theactuator. The plug isolates the FWH.

The VHBS is connected to the samecontrol system and works in parallel withthe VHB-3.

When the FWH is isolated, the dump

valve is opened to depressurize and drainthe FWH and piping. The internalpressure in the valves acting on theplugs secures the plug posit ion inbypass mode.

The manual hand wheel is turned to lockthe plug-stem

The hand wheel is secured with a padlock.

When the limit switches for the plug andthe hand wheel are activated, the on/offvalve B can be closed


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VHB valves with water hydraulicFrom Bypass mode to normal mode

The hand wheel shall beturned back to release the

plug.

The dump valve shallclose and the on/off valveB shall stay closed.

The filling valve wil lrefil l/pressurize the FWHand piping.

When the pressure isequalized the plug wil l

move to normal posit ion

The valve is now back innormal mode operation.

VHB-T3WH


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Boiler feedwater heater bypass integrated water hydraulic control system


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Why CCI system?

The pressure drop over each valve can be aslittle as 0.5 bar (7psi) on normal mode.

Quick opening to the tune of 5sec.

No standby valves or parallel piping.

No leakage through bypass ports whensystem on normal mode

No additional gate valves required.

Prevents tube rupture

No spring loaded safety valves Cheaper and reliable


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Valve Body

The valve is manufactured from fully

machined forgings with a body shape ofsmooth design and all body penetrationscircular to prevent asymmetrical stresspatterns.

Connections are adapted to the connectingpiping.

Material is typically carbon steel, WB36 orCrMo low alloy steel.


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Bonnet

Pressure seal bonnet is standard whichprovides a safe and tight connection that iseasily assembled and disassembled.

All internal parts can be removed through thebonnet cavity.

Material is typically CrMo low alloy steel, butcan be Carbon Steel if required.


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Typical VHB 3 General Arrangement


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Typical VHB 2 General Arrangement


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Documents

VHB Presentation [Compatibility Mode].pdf