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China Suppliers Factory Class 900 Fully Welded Trunnion-Mounted DBB Gas Ball Valve with Gear Operator for High Reliability
Key Features
Double Block-and-Bleed (DBB) Configuration
Provides secure pipeline isolation and safe cavity pressure relief, preventing leaks and ensuring safe operation in gas transmission systems.
Trunnion-Mounted Ball Design
Maintains stable sealing under high-pressure and large-diameter conditions, extending valve life and reducing wear in gas pipelines.
Gear-Operated Mechanism
Low-torque, smooth manual operation for precise control, even under full pressure, ensuring ease of use in critical gas applications.
Safety Features for Critical Gas Applications
Includes fire-safe seats, anti-static protection, and anti-blowout stem, providing enhanced safety in high-pressure, flammable gas environments.
Versatile Material Options
Customizable materials, including Carbon Steel, Stainless Steel, Alloy Steel, and PCTFE, ensure compatibility with various gas media, temperatures, and project requirements.
Frequently Asked Questions
Q
What is a Double Block-and-Bleed (DBB) ball valve and when is it required?
A Double Block-and-Bleed (DBB) ball valve provides two independent seating surfaces that block flow simultaneously while a bleed port between them relieves cavity pressure. It is required in gas transmission systems where positive isolation must be confirmed for maintenance, emergency shutdown, or regulatory compliance purposes.
Q
How does a trunnion-mounted ball valve differ from a floating ball valve?
In a trunnion-mounted ball valve, the ball is mechanically anchored by upper and lower trunnions, keeping it in a fixed position. This means line pressure does not push the ball against the downstream seat, significantly reducing operating torque and seat wear. Floating ball valves lack this support, making trunnion designs preferable for high-pressure, large-diameter pipelines.
Q
What are the advantages of a gear-operated mechanism on a ball valve?
A gear-operated mechanism multiplies the applied manual force through a gearbox, allowing operators to achieve smooth, precise valve control with low torque effort—even under full operating pressure. This is especially beneficial for large-bore or high-pressure valves where direct wrench operation would require excessive force and could lead to operator fatigue or inaccurate positioning.
Q
What does "fire-safe" design mean for a ball valve?
A fire-safe ball valve is engineered to maintain sealing integrity when exposed to fire. In a fire event, soft polymer seats may be damaged, but fire-safe designs incorporate secondary metal-to-metal seats that engage automatically to prevent gas leakage. This feature meets standards such as API 607 and BS 6755 Part 2, which are mandatory for valves used in flammable gas environments.
Q
Which material should I choose for my ball valve — Carbon Steel, Stainless Steel, or Alloy Steel?
The choice depends on your operating conditions. Carbon Steel (e.g., ASTM A216 WCB) is suitable for standard pressures and temperatures with non-corrosive media. Stainless Steel (e.g., 316L) is recommended for corrosive or sour gas environments. Alloy Steel (e.g., ASTM A217 WC6) handles elevated temperatures and pressures. PCTFE seat materials offer excellent chemical resistance and low gas permeability for specialized applications.
Q
What anti-static protection is included, and why is it important?
Anti-static protection consists of conductive spring-loaded devices between the ball, stem, and valve body that provide a continuous electrical path to earth. In flammable gas environments, static electricity generated by gas flow could otherwise cause dangerous sparks. Anti-static devices dissipate this charge safely, meeting requirements of standards such as API 6D and BS EN ISO 17292 for use in explosive atmospheres.