Bellows Valve Introduction
- Dec 09, 2017 -

Bellows Valve Introduction

Contents

 

Bellows Valve Structure Introduction

Bellows Valve Feature

Bellows Valve Design Parameter

Bellows Valve Working Principle

Bellows Valve Inspect and Test

Bellows Valve application on BYC



1. Bellows Valve Structure Introduction


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Bellows Valve Main Parts

Body, Wedge (Disc), Seat, Bellows Unit, Bonnet Connected Components, Column, Crossbeam, Stud and Nuts


Bellows Parts

Metal Bellows, Packing Box and Bellows Seat

 

Bonnet Fittings Unit

Flange and Fittings welded or forged integrally











2. Bellows Valve Feature


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Packing box and bonnet are welded connection in bellows units

 

Bellows seat and down stem are welded connection

 

Body and bonnet fittings unit are also welded connection or lens surface connections













2 outer leakage pots of usual valve

-body and bonnet connection

-packing seal

 

Bellows Valve Sealing Measure

Leakage pot is adopted of welded connection or reserved lip welding neck collar after bolted connection

Double sealing of bellows and packing, bellows is main sealing, packing is associated sealing.

Valve owns back seal structure and sealing is reliable.

 

Bellows is located in the bonnet inner cavity, avoiding directly sluicing with medium, increase service life. 


Bellows is adopted of 2~6 level overlapping, preventing valve leakage caused by only one level breakage, increase service life.

 

Sealing surface is overlaying hard alloy metal, better on abrasion resistance, corrosion resistance and scratch resistance, according customer requirement, increase service life.

 

 

3. Bellows Valve Design Parameter

 

Diameter: 15~600mm, 1/2”~24”

Pressure: 150LB, 300LB, 600LB, 800LB, 900LB, 1500LB

Suitable temperature: 400

 

Suitable medium: Hydrogenated terphenyls, hydrogen, hot oil, chlorine and others flammable, explosive, poisonous and radiatiive mediums.


Main material: A105, 25, WCB, CF8, 304, 304L, 316, 316L


Bellows material: 304, 304L, 316, 316L, Inconel 600, Inconel 625, Inconel 718


Bellows unit usually is “U” pattern structure, high pressure bellows is pressed of multilayer bellows to meet requirement of compression resistance.


Freign suppliers type is “Ω” structure bellows unit, that the wave height of bellows is larger, length of bellows is shorter. We use same structure on 1500LB domestic valves.



Chart 1: Bellows main parameter comparison

Valve Size

Open height

Class

Structure

Material

Outer Dimension

Inner Dimension

Wave Height

2”

42

800LB

U Pattern

1Cr18Ni9Ti

39

28

5.5

2”

42

1500LB

ΩPattern

Inconel 625

48

34

7

Valve Size

Wave Distance

Class

Layers

Single Layer Thickness

Displacement

Flexible Amount

Bellows Length

2”

5

76

4

0.25

±21

11%

380

2”

5.74

61

5

0.30

±21

12%

350




4. Bellows Valve Working Principle


Valve shut off: Revolve handwheel clockwise, stem nut drive stem down and close valve.

 

When close valve, stem drive bellows down, and bellows is in tension after valve closed.

 

Valve shut on: Revolve handwheel anticlockwise. Bellows is in compression state after valve fully open.

 

 

5. Bellows Valve Inspect and Test


Chart 2: Bellows valve test items and methods

Item

Test

Test Methods

1

Air Seal Test

Valve is closed halfway, press 0.6MPa to test medium in valve cavity, then close valve and do leakage test, test medium is atmospheric

2

High Seal Test

Close valve, press 1.1 times of nominal pressure from inlet port to test medium, test medium is water which temperature is no higher than 52(antirust is additive)

3

Shell Test

Valve is closed halfway, press 1.5times of nominal pressure into cavity to test medium, test medium is water which temperature is no higher than 52(antirust is additive)

4

Helium Mass Spectrometer Leak Test

When standard atmospheric pressure and temperature under 20, fix valve with Helium Mass Spectrometer Leak equipment which sensitivity is 10-6 ml Helium/s and pump vacuum, when vacuum degree reaches 5Pa in valve body, using pure Helium to test welding seam and welding groove one by one in spray method.


Valve usual test standards

API 598 <VALVE INSPECT AND TEST>

JB/T9092 <VALVE INSPECT AND TEST>

 

Bellows unit inspect and test

Bellows unit and stem welded test

Bellows valve whole set inpsec and test after assembling



Bellows unit inspect and test


Diagramme 3 

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1. Down bellows seat


2. Bellows


3. Packing box









Diagramme 4

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1. Down stem


2. Down bellows seat


3. Bellows


4. Packing box






Chart 3: Bellows and bellows unit test items


Sr.No.

Test Item

OQC

Type Test

Test Method

1

Seal Test

Compulsory

Compulsory

Test with Helium mass spectrometer leak testing device which sensibility is 10-6 ml He/s

2

Pressure Test

Compulsory

Compulsory

Hydraulic test with 1.5 times of nominal pressure

3

Cycle Life

/

Compulsory

Test in nominal pressure, way of pressure and test pressure are same, cycle frequency can’t over 1pcs per second



Bellows unit and stem welded connection test

Welded way: Argon arc welded

Test medium: Compressed air

Test pressure: 0.6MPag

Continous time: 3Min

 

6. Bellows Valve application


Bellows valve working condition

Flammable, explosive, poisonous, high permeability and radiatiive special mediums and industrial pipes on atrocious condition

Nuclear power items and confined space on ships

 

Bellows valve application on BYC

EO/EG equipment, BCC ethylene, Minibuses EPS device