Trunnion vs. Floating Ball Valves: Key Differences and How to Choose

The main difference is how each valve supports its ball. In a floating ball valve, the ball is not fixed to a trunnion and can move slightly under line pressure, pressing against the downstream seat to help shut off flow. In a trunnion-mounted ball valve, the ball is supported by upper and lower shafts, while the seats move toward the ball. Floating designs are often considered for smaller or lower-pressure services, while trunnion designs are commonly evaluated for larger sizes or higher differential pressures. The right choice depends on pressure, size, operating frequency, sealing requirements, and the full service conditions—not valve type alone.

Click here to get more.

Comparison Scope: What We Mean by Each Design

This comparison focuses on the ball-support and seating arrangements used in industrial quarter-turn ball valves. Both designs open and close by rotating the ball, typically through 90°, and both can be specified with different body styles, materials, end connections, and seat options. Product limits vary by manufacturer and configuration, so verify pressure-temperature ratings and applicable standards on the specific datasheet.

Quick Difference Summary

Key Design Differences

Ball Support and Seat Loading

A floating ball is not rigidly anchored by support shafts. When pressure acts across a closed valve, the ball can move downstream and load the downstream seat, creating the sealing contact. This arrangement is mechanically straightforward, but the pressure force acting on the ball and seat can influence both sealing load and operating torque.

A trunnion-mounted ball is restrained by support shafts, so it does not shift downstream in the same way. Instead, the seats are designed to move toward the ball, often using springs and pressure forces according to the valve design. This arrangement can reduce the load transmitted through the ball to the stem, but it does not mean that every trunnion valve has lower torque or better shutoff in every service.

Pressure, Size, and Operating Torque

Pressure-related force helps explain why valve size matters. As a simplified illustration, a differential pressure of 10 bar (1 MPa) acting across a projected circular area of 100 mm diameter corresponds to approximately 7.9 kN of force, using pressure multiplied by area. This is an illustrative calculation rather than a valve rating; actual loads depend on geometry, seat design, friction, and operating conditions.

As bore size and differential pressure increase, designers must account for the resulting forces when selecting the ball, seats, stem, and actuator. Trunnion construction is therefore frequently considered for larger-bore or higher-pressure duties. A floating design may still be appropriate where its particular pressure class, size, materials, and torque requirements meet the application specification.

Goto KAIWEI VALVE to know more.

Application Suitability Comparison

When a Floating Ball Valve May Be a Good Fit

Consider a floating ball valve when the required size and pressure class are within the manufacturer’s stated limits and the process benefits from a simpler construction. It may suit general isolation duties in process lines, utility systems, or equipment packages, provided the media, temperature, cycling, and leakage requirements are compatible with the selected seats and materials. Confirm the operating torque at the actual differential pressure, especially if the valve will be automated.

When a Trunnion-Mounted Ball Valve May Be a Good Fit

Evaluate a trunnion valve when the line size or pressure conditions make ball support and operating torque central selection concerns. It may also be appropriate when the project specification calls for features such as double block and bleed, but buyers should confirm the exact valve construction and test arrangement rather than infer capability from the word “trunnion.” For critical isolation duties, specify the required leakage acceptance, seat arrangement, and inspection or testing requirements.

Cost, Lead Time, and Sourcing Considerations

Purchase price depends on more than the support design. Size, pressure class, body and trim materials, seat compounds, fire-safe or other project requirements, actuation, end connections, inspection, and documentation can all affect the quotation. A floating valve may offer a cost advantage in some configurations, while the specific cost comparison can change with size, options, and supplier production scope.

Lead time should also be confirmed against the required configuration and quantity. Standard materials or common specifications may be easier to source than special alloys, nonstandard dimensions, or project-specific testing, but availability varies by supplier and order timing. For a fair comparison, request equivalent datasheets and quotations for both designs, including actuator sizing, accessories, documentation, and delivery terms.

How to Choose: A Practical Decision Framework

1. Define the service. Provide the fluid, normal and maximum pressure, differential pressure across the closed valve, temperature range, and any solids or corrosive components.
2. Confirm size and pressure class. Compare the required line size and rating with the supplier’s stated limits for each proposed design.
3. Set the shutoff requirement. Identify the required leakage criterion, seat arrangement, and any project-specific testing or isolation features.
4. Check operation and automation. Ask for operating torque across the specified conditions, including any relevant breakaway torque, and verify actuator sizing against the submitted data.
5. Compare total supply scope. Review materials, ends, accessories, inspection, documentation, quantity, and delivery schedule—not just the valve’s base price.

Common Selection Mistakes to Avoid

• Choosing by pressure class alone. A pressure class does not replace checking temperature limits, differential pressure, material compatibility, and shutoff requirements.
• Assuming one design always has lower torque. Torque depends on the valve’s construction, size, pressure, seat materials, and service conditions. Request application-specific figures.
• Treating “trunnion” as a complete feature specification. Confirm seat behavior, cavity relief, drain or vent provisions, and any double block and bleed requirements on the actual datasheet.
• Comparing non-equivalent quotations. Ensure both offers cover the same materials, ratings, accessories, testing scope, and documentation.

Key Takeaways

• A floating ball shifts under line pressure to load the downstream seat; a trunnion ball is supported by shafts and uses a seat arrangement designed to seal against the supported ball.
• Floating designs can be suitable for many general isolation duties when size, pressure, torque, and material limits are met.
• Trunnion designs are often evaluated for larger or higher-pressure service, but suitability must be confirmed from the specific product data.
• Compare application-specific torque, shutoff requirements, materials, options, and total sourcing scope before making a final selection.

Final Recommendation

Choose a floating ball valve when its verified size, pressure-temperature rating, sealing performance, and operating torque fit the service and project specification. Choose a trunnion-mounted valve when the supported-ball arrangement better addresses the application’s size, pressure, or operating requirements, and confirm any additional isolation features on the datasheet. Neither design is universally superior; the best choice is the one documented to meet the actual process conditions.

For a project comparison, share the line size, fluid, pressure and temperature range, required shutoff, operation type, and quantity with KAIWEI VALVE. Our team can review the application details and provide a product proposal for evaluation, with the relevant configuration and technical information for your procurement process.

If you are looking for more details, kindly visit Trunnion vs. Floating Ball Valves:.