Bellows Gate Valve | Zero Leakage | DN15–DN800

The Bellows Gate Valve is a linear isolation valve using a flexible metal bellows for zero-emission stem sealing. The disc moves linearly for on-off control; the bellows between stem and bonnet forms a metal barrier completely eliminating fugitive emissions. Bellows (AISI 633/316L/Hastelloy) are 100% helium-tested, with dual bellows + graphite packing backup seal for redundant safety. Multi-wall anti-torsion bellows give 10,000-cycle life; CoCr hardfaced disc and seats give wear resistance. DN15–DN800, PN16–PN260, -101~650°C, WCB/A105N/CF8/CF8M/LF2, flanged/BW/SW/threaded, manual/pneumatic/electric. Per API 602, ISO 15761, GB 12221, JB/T 11487, ISO 15848-1.

1. Absolute Zero-Leakage Bellows Sealing: Adopting high-quality metal bellows (AISI 633 / AM 350, stainless steel 316L, or Hastelloy, customizable) manufactured with automatic roll welding technology, the bellows is welded to the valve stem at the lower end and fixed between the valve body and bonnet at the upper end, forming a complete static and dynamic sealing system. All bellows are 100% tested by helium gas leak detection, and the entire valve undergoes strict sealing tests to ensure zero leakage at the valve stem, fully complying with ISO 15848-1 fugitive emission and EPA environmental standards - eliminating the chronic stem leakage problem of conventional packed gate valves.

2. Dual Safety Seal (Bellows + Graphite Packing): Equipped with a dual sealing structure of "metal bellows + graphite packing" for redundant safety. The bellows is the primary seal providing hermetic zero-emission isolation; even if the bellows is accidentally damaged by fatigue, corrosion, or over-pressure, the backup graphite packing immediately takes over sealing, preventing medium leakage and avoiding safety accidents. This design greatly improves reliability and safety in critical applications handling toxic, flammable, explosive, or high-value media where any leakage is unacceptable.

3. Long Service Life & Durable Construction: The metal bellows adopts an extended, multi-wall, and anti-torsion design with an opening and closing life of up to 10,000 cycles - far exceeding the industry average and ensuring long-term reliable operation. The valve disc and seat are hardfaced with CoCr (cobalt-chromium) alloy, providing excellent wear resistance, corrosion resistance, and anti-friction performance. The valve body is made of high-strength cast steel (WCB), forged steel (A105N), or stainless steel (CF8/CF8M/F304/F316/A350 LF2), withstanding extreme working conditions and reducing maintenance frequency and cost.

4. Wide Temperature & Pressure Range: Suitable for working temperatures from -101°C to 650°C and pressure ranges from PN16 to PN260 (ANSI Class 150 to Class 1500), adapting to harsh environments including cryogenic service (LNG facilities), high-temperature steam, and high-pressure process systems. Low-temperature carbon steel (A350 LF2) bodies are available for cryogenic service, while alloy and stainless steel options cover high-temperature and corrosive applications. It is especially suitable for LNG facilities, nuclear power plants, and other special scenarios requiring strict temperature and pressure control.

5. Self-Cleaning Conical Disc & Stable Operation: The valve disc adopts a conical design that automatically scrapes and removes impurities from the sealing surface during closing, ensuring reliable sealing performance even with media containing particulates. The 360° free-rotating valve disc design avoids vibration transmission to the valve stem, reduces operating noise, and improves operation stability. For valves with DN > 150, a triangular positioning device is added to protect internal components from vibration and enhance tensile strength during high-cycle operation.

6. Multiple Connections, Drives & Easy Maintenance: Standard connection methods include flange (RF/RTJ), butt welding (BW), socket welding (SW), and thread (NPT/SW, per ASME B16.11 / HG 20592), compatible with international pipeline standards for easy installation and replacement. Operation modes include manual (crank handle / gear), pneumatic, and electric (customizable with explosion-proof and remote control). The overall structure is simple, wearing parts are easy to disassemble and maintain, reducing production line downtime. Maintenance manuals are provided in 24 languages for global customers, and full technical support is available for sizing, installation, and commissioning.

The Bellows Gate Valve operates on the wedge gate principle with metal bellows replacing stem packing. Handwheel turns stem; Acme threads lift CoCr conical disc: open, it retracts for unobstructed flow; closing, it wipes the seat for zero leakage. Bellows (AISI 633/316L/Hastelloy, roll-welded) welded to stem and fixed between body/bonnet - it compresses/extends with stem movement, hermetically eliminating fugitive emissions. Backup graphite packing gives secondary containment. Bellows 100% helium-tested; valves per API 598, ISO 15848-1. 360° rotating disc isolates vibration.

Oil & Gas Industry: Oil exploration, refineries, natural gas pipelines, and LNG facilities, used for on-off control of crude oil, natural gas, liquefied natural gas, and other hydrocarbons. The zero-leakage bellows seal prevents fugitive emissions of flammable and explosive media, ensuring plant safety and environmental compliance in upstream, midstream, and downstream oil & gas operations.

Petrochemical & Chemical Industry: Chemical plants and fertilizer plants handling corrosive and hazardous media such as chlorine, hydrofluoric acid, phosgene, bisphenol A, and isocyanates. The hermetic bellows seal prevents toxic and corrosive medium leakage to the atmosphere, protecting personnel and the environment, while the dual backup seal provides an additional safety layer for critical chemical processes.

Power Generation Industry: Thermal power plants, nuclear power plants, and steam systems, used for controlling high-temperature and high-pressure steam, feedwater, and cooling water. The bellows seal eliminates steam leakage and associated energy loss, while the wide temperature range (-101°C~650°C) and CoCr hardfaced seats ensure reliable long-term service in demanding power station conditions.

Pharmaceutical Industry: Pharmaceutical production lines handling high-purity media that require no pollution and zero leakage. Stainless steel (316L) bodies with polished internals and hermetic bellows sealing prevent both ingress of atmospheric contaminants and egress of valuable or hazardous product, meeting GMP and cleanroom requirements for pharmaceutical manufacturing.

Other Industries: Vacuum systems (where the bellows prevents air ingress), refrigeration systems, hot oil systems, cold and hot water systems, textile and printing/dyeing industries, and any application handling toxic, flammable, expensive, or environmentally sensitive media where conventional packing leakage is unacceptable.

Every Bellows Gate Valve is manufactured and tested per API 602, ISO 15761, GB 12221, ISO 15848-1, ISO 9001. Raw materials MTR-verified with chemical/mechanical tests for all body and bellows materials. Each bellows 100% helium-tested before assembly. Valves get dimensional check, shell 1.5×, seat 1.1× per API 598, plus helium bellows seal test. CoCr disc/seats 100% inspected, hardness checked. Bellows cycle-tested to ≥10,000 cycles. Graphite packing verified for compression. Actuators tested. Units ship with MTR, helium report, test cert, 18-month warranty, BV/SGS/TUV on request.

Q1: What is a bellows gate valve and why use bellows instead of conventional packing?

A: A bellows gate valve is a wedge gate valve that uses a flexible metal bellows assembly instead of conventional compression packing to seal the valve stem. In a conventional packed gate valve, the stem passes through packing (graphite, PTFE, etc.) that is compressed by a gland to create a seal - but because the stem moves linearly through the packing during every operation, some degree of stem leakage (fugitive emission) is inevitable over time, especially with thermal cycling, wear, and packing degradation. A bellows gate valve eliminates this by welding a flexible metal bellows tube around the stem: the lower end is welded to the stem, the upper end is sealed between body and bonnet, creating a completely hermetic metal barrier. As the stem moves up and down, the bellows simply compresses and extends - there is no sliding seal interface, so zero leakage is achievable. This is critical for toxic, flammable, explosive, radioactive, expensive, or environmentally regulated media where any leakage is unacceptable, and for vacuum service where air ingress must be prevented.

Q2: What is the bellows made of, and how long does it last?

A: The bellows is typically made from AISI 633 (also known as AM 350 - a precipitation-hardening stainless steel with excellent fatigue strength and corrosion resistance), stainless steel 316L (for general corrosive service), or Hastelloy (for highly corrosive and high-temperature applications, customizable). The bellows is manufactured by automatic roll welding of multiple thin-wall convolutions into an extended, multi-wall, anti-torsion tube, then 100% helium leak-tested before assembly to verify zero porosity and weld integrity. Our bellows are designed and type-tested for a minimum cycle life of 10,000 open-close operations without failure - far exceeding the industry average of typically 2,000–5,000 cycles. Actual service life depends on operating conditions: temperature, pressure, medium corrosiveness, cycle frequency, and thermal cycling all affect fatigue life. For high-cycle or extreme-temperature applications, we recommend specifying Hastelloy bellows and selecting a valve with oversizing margin to reduce bellows stress. Bellows are replaceable during major overhaul.

Q3: What happens if the bellows fails - is there a backup seal?

A: Yes - every bellows gate valve is equipped with a dual sealing structure: the metal bellows is the primary seal, and a graphite packing set installed above the bellows (between the bellows and the external environment) serves as a secondary backup seal. In normal operation, the bellows provides hermetic zero-emission sealing and the graphite packing is essentially idle. If the bellows is ever damaged by fatigue cracking, corrosion, over-pressure, or mechanical abuse, the graphite packing immediately takes over the sealing function, preventing or significantly limiting medium leakage to the atmosphere - buying time for safe shutdown and maintenance rather than causing an immediate catastrophic leak. This dual-seal design is a critical safety feature for hazardous media applications. We recommend periodic monitoring for any signs of leakage at the packing area, as this would indicate a bellows failure requiring scheduled replacement. The backup packing can be adjusted or repacked under pressure in some designs, but bellows replacement requires valve removal and depressurization.

Q4: What leakage and emission standards does it meet, and how is it tested?

A: Our bellows gate valves are designed and tested to meet the most stringent international fugitive emission and leakage standards: ISO 15848-1 (industrial valve fugitive emissions - classification system and qualification procedures), EPA (US Environmental Protection Agency) standards for volatile organic compound (VOC) emissions, and API 622 / API 624 where applicable. Testing protocol includes: (1) Each individual metal bellows is 100% helium leak-tested by helium mass spectrometry before assembly - this is the most critical quality check and verifies zero porosity and zero weld leakage. (2) The assembled valve undergoes hydrostatic shell strength test at 1.5× rated pressure and seat seal test at 1.1× rated pressure per API 598 and GB/T 13927. (3) A dedicated bellows stem seal test using helium mass spectrometry confirms zero stem leakage at rated pressure and temperature. (4) Type testing includes thermal cycling and mechanical cycle testing to ≥10,000 cycles with post-cycle helium leak verification. (5) Optional third-party certification by BV, SGS, or TÜV, and ISO 15848-1 certification (typically BH or CO classification) are available on request. The valve is designed for "zero leakage" performance - defined as no detectable leakage at the stem with helium mass spectrometry at sensitivity levels of 1×10⁻⁶ mbar·L/s or better.

Q5: What media and applications is the bellows gate valve suitable for?

A: Bellows gate valves are suitable for a very wide range of media and applications where zero stem leakage is required, including: (1) Oil & gas - crude oil, natural gas, LNG, refined products, and hydrocarbon processing where flammable/explosive medium leakage poses safety and environmental risks. (2) Petrochemical & chemical - chlorine, hydrofluoric acid, phosgene, isocyanates, bisphenol A, polymers, and corrosive/toxic chemicals where atmospheric leakage endangers personnel. (3) Power generation - high-temperature/high-pressure steam, feedwater, and cooling water in thermal and nuclear power plants, where steam leakage causes energy loss and safety hazards. (4) Pharmaceutical - high-purity, sterile, or expensive media where both contamination ingress and product egress must be prevented. (5) Vacuum systems - where the bellows prevents air ingress that would degrade vacuum. (6) Refrigeration, hot oil, textile/dyeing, and any application with toxic, expensive, or regulated media. The temperature range is -101°C to 650°C and pressure range PN16–PN260 (Class 150–1500), with body materials including WCB, A105N, CF8/CF8M, F304/F316, and A350 LF2 (low-temperature). It is NOT recommended for throttling/modulating service - like all gate valves, it is for fully open or fully closed on-off isolation only.

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