Bellows Type Safety Valve

1″-10″ (25~250mm)
WCB, S.S.304, S.S.316

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Bellows Type Safety Valve Descriptions

Bellows type safety valve is the ideal over pressure protection device for pressure equipment, pressure vessel and pipeline with steam or other dangerous mediums. When the medium pressure increases and exceeds the allowed pressure, the bellows safety valve will open automatically to discharge fully, protecting the medium pressure from being increased continually. When the medium pressure reduces to the set up pressure, the relief valve will close timely, making sure the equipment or the pipeline work safely.
The bonnet of full sealed safety valve is sealed, preventing the dust or foreign matters from invading into the bonnet and preventing the toxic or inflammable mediums overflow from the bonnet. Open type safety valve is good for reducing the temperature in the bonnet for its bonnet is open, which is mainly applicable to steam pipeline and vessel. The bellows safety valve with radiator is mainly applicable to the conditions of mediums with temperature 300℃ – 570℃.
The spring loaded safety valve with lever can be open with lever when the medium pressure reaches more than 75% of discharge pressure. Flowspec Luokai can produce the bellows type safety valve according to ISO4126, API RP520, JIS8210 and DIN3320. 


  • Safety valves are mostly precision castings, compact structure, nice appearance, bright surface.
  • Valve seat and body are separated type, seat is easy processing, and sealing surface is easy to grind into mirror surface, making sure on the valve sealing, convenient for disassembly and repair.
  • Reasonable designed disc holder is well-matched with nozzle ring, convenient for adjusting, which makes the safety valve discharge quickly, back to seat timely, achieving in on-off pressure difference.
  • Both valve seat and disc are Stellite welded, wear-resistance, erosion resistance, extending the valve service life.
  • Back pressure balance safety valve adopts high quality bellows, avoiding the effect of back pressure against discharge pressure.
  • The spring is processed with 2 x 24 hours constant temperature treatment, making sure the spring keep stable rigidity and correct lift in working condition.
  • Taking serious pressure testing on the valve body and seat, making sure that the safety valve work safely and reliably.


  • Design & manufacturing: ISO4126, API RP520, JIS8210, DIN3320
  • Flanged ends: ANSI B16.5a, JIS B2212-2216, DIN2546-2551
  • Face to face: API 526, JIS B2001, DIN3202
  • Inspection & testing: API 527


  • Class rating: 150LB~2500LB
  • Size: 1″-10″ (DN25~250mm)
  • Materials: steel A216 WCB, stainless steel 304 (A351 CF8), stainless steel 316 (A351 CF8M), CF3M, Monel, Hast. C
  • Set pressure tolerance: ≤±3%
  • Overpressure: ≤10%
  • Blowdown: ≤15%


  • Applicable medium: steam, air, gas, LPG, oil, corrosive liquids
  • Applicable temperature: -29℃~+350℃
  • Applicable fields: boiler, oil & gas field, steam equipment, oil vessel, pressure vessel

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