GMK Forged Steel Trunnion Mounted Ball Valve

What Is an API 6D Trunnion Mounted Ball Valve?

An API 6D Trunnion Mounted Ball Valve is a pipeline ball valve designed according to API 6D requirements, featuring a fixed ball support system instead of a floating ball structure.

In this design, the ball is held in position by the upper stem and lower trunnion. The ball does not move freely under pipeline pressure, which significantly reduces operating torque and improves valve stability.

Compared with floating ball valves, trunnion mounted ball valves are better suited for larger sizes, higher pressure ratings, and applications requiring frequent operation or automated control.

The fixed ball design provides:

Lower operating torque
Improved sealing reliability
Reduced seat wear
Longer service life
Better performance under high-pressure conditions

Working Principle of Trunnion Mounted Ball Valve

The working principle of an API 6D Trunnion Mounted Ball Valve is based on a 90-degree rotary operation.

When the actuator or handle rotates the valve stem, the ball rotates between the open and closed positions.

In the fully open position:

The bore of the ball aligns with the pipeline, allowing fluid to pass with minimum pressure loss.

In the closed position:

The ball rotates 90 degrees and blocks the flow path, creating a reliable shut-off barrier.

During operation, the trunnion supports the ball and absorbs pipeline pressure forces. This reduces the load on the valve seats and allows smooth operation even under high-pressure conditions.

Advantages of API 6D Trunnion Mounted Ball Valve

Reliable Performance for High Pressure Pipeline Systems

The fixed ball structure makes this valve suitable for high-pressure applications where conventional floating ball valves may experience excessive operating force.

The trunnion support prevents ball displacement caused by pressure, ensuring stable sealing performance in:

Oil pipelines
Natural gas transmission systems
Refinery applications
Petrochemical facilities
Energy projects

Low Operating Torque and Easy Automation

One of the main advantages of a trunnion mounted ball valve is its low operating torque.

Because the trunnion absorbs most of the pressure load, less force is required to rotate the ball. This allows the valve to use smaller actuators and provides advantages including:

Reduced actuator size
Lower operating cost
Easier automation
Improved operational efficiency

The valve can be equipped with pneumatic, hydraulic, or electric actuators according to customer requirements.

Advanced Sealing Performance

The spring-loaded seat design provides reliable sealing performance under different pressure conditions.

The seat automatically adjusts to maintain contact with the ball surface, ensuring tight shut-off during:

Low-pressure operation
High-pressure operation
Zero-pressure conditions

For critical pipeline applications, double block and bleed (DBB) design options can provide additional safety and maintenance advantages.

Fire Safe and Safe Operation Design

API 6D trunnion mounted ball valves are commonly designed with safety features for demanding industrial environments.

Typical safety features include:

Blowout-proof stem design
Anti-static construction
Fire-safe design
Emergency sealing capability
Double block and bleed function

These features help improve system safety in oil, gas, chemical, and energy applications.