A bellows sealed valve welds a metal bellows directly to the valve stem, forming a “flexible metal spacer.” This transforms the leak-prone dynamic seal between the valve stem and valve body into a static seal, achieving “zero leakage.”
It often also incorporates a packing seal, creating a “bellows + packing” double guarantee: if the bellows ruptures, the packing can temporarily seal the valve, preventing leakage.
The Importance of Bellows Sealed Valves
Excellent Sealing Performance
• Preventing Media Leakage: The bellows, a key component of bellows valves, effectively prevents leakage of media within the valve. This is particularly important for pipeline systems transporting toxic, hazardous, flammable, explosive, or valuable media, preventing safety incidents, environmental pollution, and economic losses caused by media leakage.
• Adaptable to Harsh Operating Conditions: Under harsh operating conditions such as high temperature, high pressure, and high vacuum, the sealing performance of conventional valves may be compromised. However, the bellows structure of bellows valves offers excellent flexibility and fatigue resistance, maintaining reliable sealing performance under these harsh conditions and ensuring proper valve operation.
Extended Service Life
• Reduced Packing Wear: Traditional valves typically use packing seals, which wear out due to friction over long-term use and require regular replacement. Bellows valves use bellows seals, which eliminate friction between the packing and the valve stem, reducing stem wear, extending the valve’s service life, and lowering maintenance costs and replacement frequency.
• Resistant to Media Corrosion: Bellows are generally made of corrosion-resistant materials, effectively resisting media corrosion, further improving the valve’s durability and reliability.
Excellent Operating Performance
• Reduced Operating Torque: Because bellows valves reduce friction between the packing and the valve stem, they make valve operation easier and reduce operating torque. This not only reduces operator workload but also improves accuracy and timeliness, making them particularly suitable for applications requiring frequent operation.
• Achieve Precise Control: The structural design of bellows valves enables precise control of the flow rate, pressure, and direction of the media, meeting the process requirements of diverse operating conditions.
Reliable Safety Performance
• Prevents foreign matter from entering: Bellows not only prevent media leakage but also prevent foreign matter from entering the valve interior, avoiding valve failure and damage caused by foreign matter ingress, thereby improving valve safety and stability.
• Compliance with Safety Standards: In industries with extremely high safety requirements, such as nuclear power plants and aerospace, bellows valves undergo rigorous design, manufacturing, and testing to comply with relevant safety standards and specifications, providing reliable assurance for safe system operation.
Bellows Sealed Valve Assembly
Valve Body: Made of materials such as WCB, CF8, and CF8M, this valve body is connected to the pipeline (flange/weld/threaded).
Bonnet: Mated with the valve body, bolted together to form a sealed chamber; some designs feature omega-welds or gaskets for enhanced sealing.
Disc/Seat: Made of materials such as 304 and Stellite, this valve seat engages the valve seat to provide a shutoff seal during operation. Metal or soft seals are available. Valve Stem: 20Cr13, F304, F316, etc., transmits operating force and drives the seal; requires high surface hardness and corrosion resistance.
Bells Assembly: S.S304, S.S316L double-layer or multi-layer bellows, welded to the valve stem, withstands tensile and compressive deformation and achieves zero leakage.
Packing/Gasket: Flexible graphite + stainless steel spiral wound gasket or fluoroplastic gasket, acts as a secondary seal to prevent leakage in the event of bellows failure.
Lock Nut and Spacer: Used to secure the valve opening and prevent loosening.
Grease Fitting: Included with all-stainless steel models, provides lubrication for the valve stem and sleeve.
Common Materials for Bellows Sealed Valves
Metal Materials
• Stainless Steel: Stainless steel is one of the most commonly used materials for bellows-sealed valves, offering excellent corrosion resistance, strength, and toughness.
• Hastelloy: Hastelloy offers excellent corrosion resistance, especially against highly corrosive media.
• Brass: Brass offers excellent workability and a certain degree of corrosion resistance at a relatively low cost. It is often used in applications where corrosion resistance is not particularly demanding and operating pressures and temperatures are relatively low.
• Beryllium Bronze: Beryllium Bronze offers high strength, hardness, elasticity, and fatigue resistance, as well as good corrosion resistance and electrical conductivity.
• Inconel: This nickel-based high-temperature alloy exhibits excellent high-temperature oxidation resistance.
Non-Metallic Materials
• Rubber: Rubber bellows can be used in applications where sealing requirements are high and operating pressures and temperatures are relatively low, such as in ordinary water systems or low-pressure gas systems.
• Plastics: Some plastic materials, such as polytetrafluoroethylene (PTFE), can also be used to manufacture bellows-sealed valves.
The above is information about bellows-sealed valves. If you are interested in purchasing bellows sealed valves, Newton will provide you with the highest quality products and services. Please feel free to contact us.
