Trunnion Mounted Ball Valve

Trunnion Mounted Ball Valve Industry Knowledge Extension

Understanding Trunnion Mounted Valve Technology in Critical Pipeline Applications

In modern pipeline and process systems, valve reliability, structural stability, and controlled operation are essential. Among the widely adopted solutions in medium- and high-pressure pipelines is the Trunnion Mounted Valve, a design developed to improve load distribution, sealing performance, and operational consistency under demanding conditions. This type of valve is commonly used across oil and gas, LNG, refining, petrochemical, power generation, and long-distance pipeline projects.

What Is a Trunnion Mounted Valve?

A Trunnion Mounted Valve is a ball valve design in which the ball is mechanically supported by trunnions at the top and bottom. Unlike floating ball designs, the ball is fixed in position, and axial movement is limited. This structure allows the pipeline pressure to be absorbed by the valve body and trunnion supports rather than being transferred directly to the valve seats.

This design approach helps maintain sealing stability, especially in larger diameters and higher pressure classes where seat loading must remain controlled.

Trunnion Mounted Ball Valve: Structural Characteristics

A Trunnion Mounted Ball Valve typically consists of the following key components:

• Fixed ball supported by upper and lower trunnions
• Independent floating seats, usually spring-loaded
• Robust valve body designed to carry pressure-induced loads
• Anti-blowout stem and controlled torque transmission

Because the ball is not free-floating, the operating torque remains relatively stable even as line pressure increases. This characteristic is particularly valuable in automated or remotely operated systems, where predictable actuation behavior is required.

Trunnion Type Ball Valve vs Floating Ball Valve

Understanding the differences between a Trunnion Type Ball Valve and a floating ball valve helps clarify why trunnion designs are preferred for certain applications.

Floating ball valves rely on line pressure to push the ball against the downstream seat, creating the seal. While effective for smaller sizes and moderate pressures, this design can result in higher operating torque and increased seat wear as pressure rises.

In contrast, a Trunnion Type Ball Valve uses fixed ball support and pressure-assisted seats. This reduces friction between the ball and seats, improves sealing consistency, and supports longer service intervals in continuous-duty applications.

Sealing Principles and Pressure Management

One of the defining advantages of trunnion-mounted designs is their sealing system. Spring-loaded seats maintain initial sealing at low pressure, while line pressure enhances sealing performance as pressure increases. This dual-action mechanism supports bidirectional sealing and contributes to controlled leakage performance.

In many pipeline systems, trunnion-mounted designs are also compatible with features such as:

• Double block and bleed (DBB) configurations
• Emergency seat sealing systems
• Fire-safe design concepts in accordance with applicable standards

These characteristics support safer operation during abnormal pressure conditions or emergency scenarios.

Applications Across Industrial Sectors

The Trunnion Mounted Ball Valve is widely applied in industries where operating conditions demand structural integrity and controlled performance:

• Oil and gas transmission pipelines
• LNG liquefaction and regasification facilities
• Refining and petrochemical process units
• Chemical processing plants
• Nuclear and conventional power generation systems

In long-distance pipelines, the ability of a Trunnion Mounted Valve to manage high pressure and large diameters while maintaining stable operation is particularly valued.

Material Selection and Manufacturing Considerations

Material selection plays a critical role in the performance of trunnion-mounted designs. Valve bodies and balls are commonly manufactured from carbon steel, stainless steel, or alloy steel, selected based on pressure class, temperature range, and media compatibility.

Precision machining, controlled welding processes, and dimensional verification are essential to ensure correct alignment of trunnions, seats, and sealing interfaces. For critical services, traceability and documented inspection processes support consistency in serial production.

Maintenance and Operational Benefits

From an operational perspective, Trunnion Type Ball Valves offer advantages in maintenance planning. Reduced seat wear and stable torque behavior contribute to predictable service life. In many designs, seats and seals can be serviced without removing the valve body from the pipeline, depending on configuration.

These characteristics help operators reduce downtime while maintaining system integrity across extended operating cycles.