Overview of Trunnion Mounted Ball Valves

A trunnion mounted ball valve is a type of industrial valve used to control the flow of fluids in pipelines. It consists of a spherical ball with a hole (bore) through its center, which rotates to either allow or block the flow of fluid. Trunnion mounted ball valves are distinguished by their method of support, where the ball is supported by trunnions or shafts at the top and bottom ends. Here's a detailed overview of trunnion mounted ball valves:

Overview of Trunnion Mounted Ball Valves

1. Construction:

  - Body: Typically made of metal (such as carbon steel, stainless steel, or alloy steel) to withstand high-pressure and high-temperature applications.

  - Ball: A spherical ball with a hole (bore) through its center, which rotates within the valve body to control flow.

  - Trunnions: Horizontal shafts or stubs at the top and bottom of the ball that support and guide its movement, ensuring proper alignment and sealing.

2. Operation:

  - When the valve is open, the ball rotates perpendicular to the flow direction, allowing fluid to pass through the bore.

  - When the valve is closed, the ball rotates parallel to the flow direction, blocking the passage of fluid.

3. Sealing Mechanism:

  - Seats: Soft or metal seats (often made of materials like PTFE, RPTFE, or metal alloys) provide tight sealing between the ball and the valve body to prevent leakage.

  - Seals: Additional seals, such as O-rings or V-rings, may be used to enhance sealing performance and reduce the risk of fugitive emissions.

Key Features

1. Trunnion Mounting:

  - The ball is supported by trunnions or shafts at the top and bottom ends, providing stable and precise alignment during operation.

  - This design allows for larger ball sizes and higher pressure ratings compared to floating ball valves.

2. High Pressure and High Temperature Applications:

  - Trunnion mounted ball valves are suitable for applications with high pressures, high temperatures, and abrasive or corrosive fluids.

3. Bi-Directional Sealing:

  - Trunnion mounted ball valves typically provide bi-directional sealing, meaning they can effectively seal against flow in both directions.

4. Fire-Safe Design:

  - Some trunnion mounted ball valves are designed to meet fire-safe standards, incorporating features such as secondary metal-to-metal sealing and blowout-proof stems to prevent leakage during fire incidents.

5. Anti-Static Design:

  - To prevent static electricity buildup, trunnion mounted ball valves may include anti-static devices such as spring-loaded seats or conductive components.

Applications

1. Oil and Gas Industry:

  - Pipeline transportation, refining, production, and processing facilities.

  - Onshore and offshore applications where high pressures and temperatures are encountered.

2. Petrochemical and Chemical Industry:

  - Chemical processing plants, petrochemical refineries, and specialty chemical production facilities.

3. Power Generation:

  - Power plants, including fossil fuel, nuclear, and renewable energy facilities.

4. Water and Wastewater:

  - Municipal water treatment, desalination plants, and wastewater management facilities.

5. Mining and Minerals:

  - Mining operations, mineral processing plants, and mineral extraction facilities.

Advantages

1. Stable and Precise Operation:

  - Trunnion mounting provides stable support and precise alignment of the ball, ensuring reliable operation and tight sealing.

2. High Pressure and High Temperature Capability:

  - Suitable for demanding applications where high pressures and temperatures are encountered, offering robust performance and durability.

3. Bi-Directional Sealing:

  - Effective sealing against flow in both directions, providing versatility and reliability in various flow conditions.

4. Fire-Safe and Anti-Static Features:

  - Enhanced safety features, such as fire-safe and anti-static designs, ensure compliance with industry standards and regulations.

Disadvantages

1. Complex Design:

  - Trunnion mounted ball valves may have a more complex design compared to floating ball valves, which can lead to higher initial costs and maintenance requirements.

2. Limited Low-Pressure Applications:

  - While suitable for high-pressure applications, trunnion mounted ball valves may not be as efficient or cost-effective for low-pressure applications.

Conclusion

Trunnion mounted ball valves are essential components in various industries, providing reliable control of fluid flow in high-pressure and high-temperature applications. With their stable and precise operation, bi-directional sealing capability, and robust construction, they offer versatility, durability, and safety in demanding operating conditions. By understanding the key features, advantages, and applications of trunnion mounted ball valves, engineers and operators can make informed decisions when selecting valves for their specific needs.