In industrial fluid control systems, trunnion ball valves stand out as a high-reliability solution for high-pressure, high-flow scenarios. Unlike traditional floating ball valves, their unique trunnion-supported design delivers superior sealing performance and operational stability—making them a cornerstone in sectors like oil & gas, chemical processing, and power generation.
What Is a Trunnion Ball Valve?
A trunnion ball valve is a quarter-turn valve where the spherical closure (ball) is anchored by top and bottom trunnions (pivots) instead of relying solely on the valve stem. This design ensures the ball remains aligned with the valve seats even under extreme pressure, eliminating the "floating" movement that causes wear in standard ball valves.
Key components include:
Trunnions: Support the ball, distributing pressure loads to reduce friction.
Spring-loaded seats: Maintain tight seals at low pressures (unlike floating valves, which require fluid pressure to seal).
Actuator interface: ISO 5211-compliant top flange for easy mounting of manual, electric, or pneumatic actuators.
How Does a Trunnion Ball Valve Work?
Open position: The ball’s bore aligns with the pipeline, allowing unobstructed fluid flow.
Closing process: Rotating the stem (via handwheel or actuator) 90° turns the ball to block the flow path.
Sealing mechanism: Spring-loaded seats press against the ball to create a tight seal—effective in both low and high-pressure conditions (Class 150 to 2500, PN 10 to PN 420).
Critical design advantage: The trunnions absorb pressure forces, reducing operating torque by 30-50% compared to floating ball valves.
Core Advantages of Trunnion Ball Valves
Zero Leakage Performance
Bidirectional sealing (API 6D Class VI) prevents media loss, even in critical applications like hydrocarbon pipelines.
High-Pressure & Temperature Compatibility
Suitable for -196°C to 425°C (cryogenic LNG to high-temperature steam) and pressures up to 42 MPa.
Low Maintenance Costs
Trunnion support minimizes seat/ball wear, extending service life. Many models (e.g., API 6D) feature double block and bleed (DBB) functionality for safe in-line maintenance.
Versatility
Available in soft-seal (PTFE/RPTFE) or metal-seal (Stellite alloy) configurations, compatible with corrosive media (acids, hydrocarbons) and abrasive slurries.
Key Industrial Applications
Trunnion ball valves are indispensable in:
Oil & Gas: Pipeline transmission, wellhead control, and refinery processes (compliant with API 6D/NACE MR0175 for sulfide corrosion resistance).
Chemical Processing: Handling toxic/corrosive fluids in distillation or synthesis systems.
Power Generation: Regulating steam/water flow in boilers and turbine systems.
Water Treatment: Controlling potable water, wastewater, and chemical dosing.
Selection & Compliance Tips
When choosing a trunnion ball valve:
Verify compliance with API 6D (pipeline valves) or ASME B16.34 (pressure-temperature ratings).
Opt for fire-safe designs (API 607/6FA) for flammable environments.
Match body materials (carbon steel, stainless steel, duplex) to the operating medium.
Trunnion ball valves balance durability, efficiency, and safety—making them the first choice for critical fluid control. Whether for high-pressure pipelines or corrosive chemical systems, their trunnion-supported design ensures long-term performance with minimal downtime.
