Not all ball valves are the same. One key distinction in industrial design is whether the valve is floating or trunnion-mounted. These terms describe how the ball is supported inside the body, and this difference has a big impact on sealing performance, operating torque, and pressure capability.
In a floating ball valve, the ball is held only by the stem on top and is free to move slightly inside the valve body. When pressure builds on the upstream side, it pushes the ball downstream, pressing it tightly against the seat to create a seal.
This simple and effective mechanism makes floating ball valves a popular choice in small to medium diameters and moderate-pressure systems.
Floating designs are appreciated for their compact structure, low cost, and excellent sealing with the help of line pressure. They are commonly used in general industrial piping, plant utilities, and standard shut-off applications.
However, as the valve size or pressure increases, the force of the line pressure also rises, pushing the ball more strongly against the seat. This can increase the torque needed to operate the valve and may accelerate seat wear. For this reason, floating ball valves are usually limited to around 6–8 inches in diameter and medium pressure ranges. Beyond that, a different design is needed.
A trunnion-mounted ball valve includes additional mechanical supports — called trunnions — that hold the ball firmly in place at the top and bottom. Unlike floating designs, the ball doesn’t move with pressure; instead, the seats move toward the ball, often assisted by springs or pressure in the pipeline.
This configuration provides much greater stability, reduces operating torque, and allows the valve to handle very high pressures and large diameters safely. Even under full working pressure, a trunnion valve remains easy to operate because the trunnions absorb most of the line force.
Trunnion ball valves are also used where reliability and safety are critical, such as in oil and gas transmission lines, refineries, and offshore platforms. They can include advanced features like double block and bleed, which allows both sides of the valve to seal simultaneously — an essential advantage during maintenance or system isolation.
The main trade-off is complexity. Trunnion valves have more components, making them heavier, more expensive, and slightly more demanding to maintain than floating ones. However, for large pipelines or high-pressure systems, their performance and durability justify the added investment.
For small and medium-sized piping systems at moderate pressure, a floating ball valve is usually the most practical and economical choice. It offers reliable shutoff, easy maintenance, and simplicity of design.
For high-pressure, large-diameter, or safety-critical systems, a trunnion-mounted valve is the superior option. It provides smoother operation, reduced torque, and long-term reliability in demanding environments.
In short, floating valves rely on line pressure to achieve the seal, while trunnion valves rely on mechanical support and spring-loaded seats for stability. Both maintain the core advantages of ball valves — fast operation, strong sealing, and long service life — but each is tailored to a specific scale and pressure range.
GEMELS S.p.A. designs and manufactures both floating and trunnion-mounted ball valves to meet diverse industrial needs, from compact on/off solutions to heavy-duty, high-pressure applications. Their engineering team can help you choose the most efficient and reliable configuration for your system.