Bellows Valve Introduction
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
Bellows Valve Main Parts
Body, Wedge (Disc), Seat, Bellows Unit, Bonnet Connected Components, Column, Crossbeam, Stud and Nuts
Metal Bellows, Packing Box and Bellows Seat
Bonnet Fittings Unit
Flange and Fittings welded or forged integrally
2. Bellows Valve Feature
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
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
Single Layer Thickness
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
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
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)
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)
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
1. Down bellows seat
3. Packing box
1. Down stem
2. Down bellows seat
4. Packing box
Chart 3: Bellows and bellows unit test items
Test with Helium mass spectrometer leak testing device which sensibility is 10-6 ml He/s
Hydraulic test with 1.5 times of nominal pressure
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