Ball valves are widely used in oil and gas, chemical processing, water treatment, and other industrial applications. Depending on the pipeline requirements, different ball valve designs may be used.
Two common types are floating ball valves and trunnion-mounted ball valves. Although both use a rotating ball to control the flow of media, their internal structures and sealing principles are different.
Understanding how these two designs work can help buyers and engineers select the right valve for their applications.
A floating ball valve has a ball that is held between two seat rings without being mechanically fixed at the bottom. The ball is connected to the stem, which drives it to rotate between the open and closed positions.
When the valve is closed, upstream fluid pressure pushes the ball slightly toward the downstream seat. This movement creates contact between the ball and the seat, forming a seal.
The higher the differential pressure, the greater the force pushing the ball against the downstream seat. However, increased seat loading can also result in higher operating torque.
Floating ball valves have a relatively simple construction, compact design, and generally lower manufacturing cost. They are commonly used in small- and medium-size pipelines and general industrial applications where pressure and operating conditions are within the valve’s design limits.
A trunnion-mounted ball valve uses a different support structure. The ball is fixed in position by an upper stem and a lower trunnion, allowing it to rotate without significant movement toward the downstream seat.
Instead of the ball moving toward the seat, the seat rings move toward the ball. Springs and, depending on the design, line pressure help maintain contact between the seats and the ball.
Because the ball is mechanically supported, pressure-related loads are managed through the trunnion structure rather than being carried entirely by the downstream seat.
This design helps reduce seat loading and operating torque in many larger-size and higher-pressure applications.
Trunnion-mounted ball valves are commonly used in oil and gas pipelines, petrochemical facilities, natural gas processing, and other applications where reliable isolation is important.
The main differences between these two designs are related to ball support, sealing mechanism, operating torque, and typical applications.
| Comparison | Floating Ball Valve | Trunnion-Mounted Ball Valve |
|---|---|---|
| Ball support | Supported between two seat rings | Supported by upper and lower trunnions |
| Ball movement | Moves slightly under fluid pressure | Remains largely fixed |
| Sealing mechanism | Ball presses against downstream seat | Seat rings move toward the ball |
| Operating torque | Can increase with differential pressure | Often lower in comparable larger-size applications |
| Construction | Relatively simple | More complex |
| Manufacturing cost | Generally lower | Generally higher |
| Common applications | General industrial pipelines | Larger pipelines and demanding services |
Actual performance depends on valve size, pressure rating, differential pressure, seat material, temperature, and the manufacturer’s design.
Pressure and operating torque are important considerations when selecting a ball valve.
In a floating ball valve, the ball moves toward the downstream seat under pressure. As differential pressure increases, the force between the ball and seat also increases. This can result in higher operating torque, particularly in larger valves or demanding pressure conditions.
In a trunnion-mounted ball valve, the ball is mechanically supported, and the seat arrangement helps manage the sealing force. This often makes it a suitable choice for larger pipeline systems and higher-pressure applications.
For valves equipped with pneumatic or electric actuators, operating torque must be carefully checked. The actuator should be selected based on the manufacturer’s torque data, taking into account pressure, seat materials, temperature, and operating conditions.
Neither design should be selected based on pressure class alone. The maximum differential pressure and actual service conditions also need to be considered.
Floating ball valves are commonly selected for:
General industrial pipelines
Water treatment systems
Chemical processing
Utility services
Small- and medium-size isolation applications
Their relatively simple construction makes them a practical choice for many standard pipeline requirements.
Trunnion-mounted ball valves are often used in:
Oil and gas transmission pipelines
Natural gas processing facilities
Petrochemical plants
Large-diameter pipeline systems
High-pressure isolation applications
Depending on the project requirements, trunnion-mounted designs may also include additional features such as Double Block and Bleed (DBB), cavity pressure relief, fire-safe construction, and emergency sealant injection. These features are not standard on every valve and should be confirmed in the technical specification.
There is no single design that is suitable for every application. Before choosing between a floating and trunnion-mounted ball valve, buyers should consider several factors:
Valve Size and Pressure Rating
Check the required nominal size, pressure class, and maximum differential pressure. Larger sizes and more demanding pressure conditions may favor a trunnion-mounted design, depending on the manufacturer’s available range.
Medium and Operating Temperature
The fluid medium and temperature affect the selection of seat and sealing materials. Special attention should be given to corrosive media, gas service, and applications containing solid particles.
Operating Method
For manually operated valves, operating torque affects the choice of gearbox or other operating equipment. For actuated valves, the required torque must be confirmed before actuator selection.
Sealing Requirements and Standards
Confirm whether the application requires soft seating or metal seating, bidirectional sealing, fire-safe design, or specific leakage acceptance criteria. Applicable design and testing standards should also be stated in the project specification.
Floating and trunnion-mounted ball valves are both widely used in industrial pipeline systems, but they serve different operating requirements.
Floating ball valves offer a simpler and more economical design for many general industrial applications. Trunnion-mounted ball valves are often preferred for larger sizes, higher differential pressures, and demanding pipeline services where operating torque and seat loading need to be carefully managed.
The best choice depends on the actual operating conditions, technical specifications, and project requirements.
Looking for a suitable ball valve for your project?
HengFeng supplies industrial ball valves for different pipeline applications. Contact our team with your required valve size, pressure class, material, connection type, and operating conditions. We can review your specifications and discuss a suitable valve configuration for your project.
Welcome to HENGFENG valves! We are a leading provider of high-quality valves and valve solutions for various industries.
Xian Hengfeng Electromechanical Equipment Co.,Ltd
No.15,group 3,Sanlian Village,Dazhao Street Office,Chang’an District,Xi’an City, Shaanxi Province
Yiwu Hengfeng Electromechanical Equipment Company
Zongtang 1st District, Jiangdong Street, Yiwu City, Jinhua City, Zhejiang Province
