In the fluid control industry, choosing the correct valve architecture is the primary step toward a durable system. For many engineers, the debate often centers on the floating ball valve vs trunnion ball valve. Both designs serve the same basic purpose. However, they handle mechanical stress differently, which affects the force needed to turn the valve.
Understanding the mechanical differences is vital for automation. This guide explores the “floating” and “trunnion” designs and how they affect torque calculation and actuator sizing.
Floating Ball Valve vs Trunnion Ball Valve
The primary difference between a trunnion and a floating ball valve is how the ball is supported inside the body.
Understanding a Floating Ball Valve
A floating ball valve has no mechanical anchoring system. It relies entirely on fluid pressure to press the ball against the downstream seat for tight sealing. In short, the ball “floats” between two valve seats. Floating ball valves are simpler, making them affordable and suitable for medium-pressure applications.
Understanding a Trunnion Ball Valve
A trunnion ball valve has a ball mechanically anchored by shaft (trunnions) on both top and bottom positions. This prevents the ball from moving inside the valve body, making them ideal for managing high-pressure applications. It also minimizes torque requirements, making trunnion ball valves easier to operate both manually and automatically.
Trunnion Ball Valve vs Floating Ball Valve: A Comparison Table
| Features | Floating Ball Valve | Trunnion Ball Valve |
| Design | Simple, floating ball | Anchored with trunnion support |
| Pressure Handling | Medium | High |
| Torque Needs | Higher | Lower |
| Best Applications | Medium-pressure systems | High-pressure or huge systems |
| Cost | Cost-effective | Expensive |
| Size Range | 1-6 inches | 6-48+ inches |
| Pressure Range | 150-1,480 PSI | 150-6,000+ PSI |
| Temperature Range | -20°F to 800°F | -20°F to 800°F |
| Torque at 600 PSI | 300% increase from low pressure | Consistent across pressure range |
| Cycle Life | Over 10,000 operations | Over 25,000 operations |
| Leakage Class | Class IV-V | Class VI |
Importance of Torque in Valves
Torque is the rotational force needed to turn the ball. In a manual ball valve, the operator provides this force by hand. Meanwhile, in automated systems, like electric actuated ball valves, a motor or pneumatic cylinder provides the force.
The torque requirement is much higher in a floating ball valve compared to a trunnion ball valve as the pressure increases.
In a floating valve, pipeline pressure pushes the ball into the downstream seat, increasing friction as well as the torque needed to turn it. In contrast, a trunnion valve uses bearings and a trunnion pin to support the ball. This absorbs pressure, minimizes seat friction, and keeps the required torque low, even at high pressures.
Key Factors for Torque Calculation
To approriately calculate the torque for any valve, engineers look at several factors:
- Break-to-Open Torque: The force required to start moving the ball from a fully closed position.
- Running Torque: The needed force to keep the ball moving through the 90-degree turn.
- Seating Torque: The force needed to “seat” the ball into the closed position.
For a manual ball valve, manufacturers usually provide a torque chart based on the differential pressure. However, for automated systems, you must add a safety or service factor. This is usually an extra 25% to 50% of the base torque to guarantee that the actuator can handle unexpected friction from debris or dry seals.
Actuator Sizing and Selection
Once the torque is calculated, you can proceed with sizing the actuator. Common choices involve pneumatic, hydraulic, or electric actuated ball valves.
Electric Actuated Ball Valves
These are popular in distant locations where compressed air is not available. They use a motor and gearbox to turn the valve. When sizing an electric actuator, always make sure the motor’s running and stall torques exceed the valve’s maximum torque requirement.
Manual Ball Valve Considerations
For a manual ball valve, sizing is about the length of the handle or the gear ratio of the handwheel. If the torque is too high for a human to turn comfortably, a gearbox is added to reduce the additional effort.
Conclusion
Selecting between a floating ball valve vs trunnion ball valve heavily depends on your pressure requirements and automation needs. Floating valves are cost-effective for low-pressure systems but expensive to automate at larger sizes. Trunnion ball valves provide a robust alternative, using fixed supports to lower friction and simplify actuator sizing.
By correctly calculating torque and understanding the mechanical differences discussed above, you can ensure a long-lasting and efficient flow control system.
Onero Valve manufactures valves compliant with API 607 and ISO 9001 standards, including both floating ball valve and trunnion ball valve options. We ensure that every valve is tested for precise torque specifications, making actuator sizing easier and less time-consuming for our clients.
Whether you need a standard manual ball valve or a fully automated solution, Onero Valve has the engineering expertise to support your infrastructure. Learn more about our technical capabilities on our website.
