Trunnion Ball Valve: Structure, Benefits, and Industrial Applications

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What is a Trunnion Ball Valve?

A trunnion ball valve is a type of quarter-turn valve where the ball is mechanically anchored by trunnions at the top and bottom. Unlike floating ball valves, the ball in a trunnion design does not move with the pressure of the fluid. Instead, the seats are spring-loaded and move toward the ball to create a tight seal. This design is ideal for high-pressure and large-diameter applications.

Key Components of a Trunnion Ball Valve

• Ball: Has a hole (bore) that aligns with the pipeline in the open position.


• Trunnions: Upper and lower extensions that secure the ball and prevent axial movement.


• Seats: Typically spring-loaded, providing a tight seal by pressing against the ball.


• Stem: Connects the actuator or handle to the ball for rotational movement.


• Body: Houses all internal parts and can be two- or three-piece for easier maintenance.

How Trunnion Ball Valves Work

When the valve handle or actuator rotates the stem 90 degrees, the ball turns accordingly to allow or block flow. Because the ball is held in place by trunnions, it does not shift with fluid pressure. Instead, the seats are designed to move slightly toward the ball to maintain the seal, which minimizes wear and operating torque.

Materials Used

Trunnion ball valves are available in a wide variety of materials to suit industrial environments:

• Carbon Steel


• Stainless Steel


• Duplex Steel


• Alloy Steels (e.g., Inconel, Monel)

Advantages of Trunnion Ball Valves

• Low Operating Torque: Less effort is needed to operate the valve due to the trunnion-supported ball.


• Tight Sealing: Spring-loaded or pressure-activated seats ensure effective sealing, even under high pressure.


• Durability: Less stress on the ball and seats means reduced wear over time.


• Size Range: Ideal for large-diameter pipelines, typically from 2 inches to 60 inches or more.

Common Applications

Trunnion ball valves are widely used in industries where durability, safety, and high performance are critical:

• Oil and Gas: For upstream, midstream, and downstream applications, including pipelines and refineries.


• Petrochemical Plants: Suitable for handling volatile and corrosive chemicals.


• Power Generation: Used in steam, water, and fuel lines.


• Water Treatment: Applied in high-pressure water handling systems.


• Industrial Processing: Handles gases, slurries, or high-viscosity fluids.

Trunnion vs. Floating Ball Valve

The main difference between trunnion and floating ball valves lies in how the sealing is achieved and the ball’s movement:

• Floating Ball Valve: Ball moves slightly with pressure to press against the seat.


• Trunnion Ball Valve: Ball is fixed; seats move to seal.


• Best For: Floating is ideal for low-pressure systems; trunnion is better for high-pressure and large-scale systems.

Maintenance and Safety

Trunnion ball valves are designed for longevity and low maintenance. However, regular inspections are essential in industrial applications. Features like emergency sealant injection systems, anti-static devices, and fire-safe designs enhance operational safety.Visit our websitehttps://www.bjmvalves.com/ for more details.

Conclusion

Trunnion ball valves offer high reliability, low torque operation, and excellent sealing for demanding industrial applications. With their robust construction and suitability for large, high-pressure systems, they are a go-to choice for oil and gas, power, and chemical industries. Selecting the right material and configuration can ensure optimal performance and longevity.

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