In the complex landscape of industrial flow control, the ball valve remains the most versatile and widely utilized component for isolation service. However, for project engineers and procurement specialists, the choice between a floating design and a trunnion-mounted design is a decision that impacts the entire lifecycle of a pipeline. Since its establishment in 2012, FTK has grown into a premier industrial valve manufacturer, specializing in high-precision ball valve solutions for the global water, oil, and gas sectors.
Understanding the mechanical nuances between these two designs is essential for ensuring system integrity, especially under high-pressure or high-temperature conditions. As a trusted valve supplier, FTK provides this comprehensive guide to help technical teams optimize their selection process and reduce long-term operational risks.
To understand the difference between floating and trunnion designs, one must first understand how a ball valve creates a seal. At its simplest, a ball valve uses a spherical disc with a hole through the center. When the valve is closed, the ball blocks the flow path. However, the way the ball interacts with the valve seats determines the valve’s pressure rating and suitability for specific environments.
In a floating ball valve, the ball is not fixed to the valve body by any mechanical support other than the stem at the top and the two seats at the sides. This allows the ball to “float” or shift slightly in the direction of the flow.
When the valve is closed and pressure is applied from the upstream side, the pressure forces the ball against the downstream seat. This mechanical displacement creates a tight, leak-proof seal. The Floating Ball Valve from FTK is engineered to leverage this “pressure-assisted” sealing, making it highly efficient for low-to-medium pressure applications.
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The primary advantage of the floating design is its simplicity and cost-effectiveness. However, as the pressure or the size of the valve increases, the force exerted on the downstream seat becomes immense. This can lead to seat deformation or high operating torque, which is why floating designs are typically limited to smaller diameters (usually up to 10 or 12 inches) and lower pressure classes (up to ANSI 300 or 600).
Unlike the floating design, a Trunnion Mounted Ball Valve features additional mechanical support at the bottom of the ball, known as the trunnion. The ball is held firmly in place by the stem and the trunnion, meaning it cannot shift downstream under pressure.
Since the ball is fixed, the sealing is achieved by the seats moving toward the ball. These valves utilize spring-loaded seats that are pushed against the stationary ball by the fluid pressure. This design ensures a consistent seal on both the upstream and downstream sides simultaneously.
Because the ball is supported by bearings, the friction is significantly lower than in a floating design. This results in much lower operating torque, even at extremely high pressures (ANSI 1500 or 2500). For large-scale infrastructure projects, FTK’s trunnion solutions provide the mechanical stability required for 24-inch pipelines and beyond.
The most significant engineering difference between the two is the relationship between line pressure and the force required to turn the valve.
For floating ball valves, horizontal installation is preferred. In vertical lines, the weight of a large ball can lead to uneven seat wear. Trunnion valves, due to their fixed axis, are more resilient in vertical orientations but still require careful alignment to ensure the spring-loaded seats function correctly.
To minimize turbulence and erosion on the ball surface, we recommend a straight pipe run of at least 5 times the nominal pipe diameter (5D) before the valve inlet. This ensures a laminar flow that protects the precision-ground surface of the FTK ball.
The choice of seat material is as critical as the valve design.
One of the hallmarks of a professional trunnion-mounted valve is the Double Block and Bleed (DBB) capability. This allows the operator to vent the body cavity while the valve is in the closed position to verify that both seats are sealing correctly. Furthermore, FTK’s high-pressure trunnion valves often include Emergency Sealant Injection ports, allowing maintenance teams to inject specialized grease to stop minor leaks without shutting down the entire line.
| Feature | Floating Ball Valve | Trunnion Mounted Ball Valve |
| Sealing Principle | Ball moves toward the seat | Seat moves toward the ball |
| Size Range | Small to Medium (up to 12″) | Medium to Large (up to 60″) |
| Pressure Class | Low to Medium (up to Class 600) | High (up to Class 2500) |
| Operating Torque | High (increases with pressure) | Low (supported by trunnion) |
| Common Use | Process plants, utilities | Transmission pipelines, Oil & Gas |
| Key Advantage | Cost-effective, simple design | Safety in high pressure, DBB capability |
Q1: When should I switch from a floating ball valve to a trunnion design? You should consider a trunnion design when the valve size exceeds 10 inches or when the operating pressure reaches ANSI Class 600 and above to manage torque and safety.
Q2: What is a Double Block and Bleed (DBB) function in ball valves? DBB is a safety feature in trunnion valves that allows the cavity between the two seats to be drained or vented while the valve is under pressure to verify seal integrity.
Q3: Can FTK provide fire-safe certified ball valves? Yes, since 2012, FTK has manufactured fire-safe ball valves that utilize secondary metal-to-metal sealing to maintain integrity if the soft seats are destroyed by fire.
Q4: Do floating ball valves require more maintenance than trunnion valves? Floating valves are generally lower maintenance due to their simpler design, but their seats must be inspected more frequently for deformation in high-cycle applications.
Selecting between a floating and a trunnion-mounted ball valve is a critical engineering decision that balances cost, safety, and operational efficiency. While floating valves offer an excellent solution for smaller, lower-pressure applications, the trunnion-mounted design is the indispensable choice for high-pressure, large-diameter pipeline infrastructure.
Since its founding in 2012, FTK has remained committed to engineering excellence as a leading industrial valve manufacturer. By combining decades of industry expertise with modern manufacturing standards, we provide high-performance solutions tailored to the specific needs of the water, oil, and gas sectors. Whether you require a standard Floating Ball Valve or a complex Trunnion Mounted Ball Valve with DBB capabilities, choosing FTK as your valve supplier ensures reliability in every turn.
For more information on our complete range of rotary solutions, please visit the FTK Products overview page.
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