Trunnion vs. Floating Ball Valves: Key Differences, Applications, and Selection

Choose a floating ball valve for many smaller-bore, lower- or moderate-pressure services where the ball can move slightly against downstream seating. Choose a trunnion ball valve when larger bore, higher differential pressure, or more demanding operating torque makes mechanically supported ball construction a better fit. Neither design is universally superior: the right choice depends on pressure and temperature conditions, media, size, operating frequency, and the applicable project specifications.

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Both valve types use a rotating ball with a bore to open or block flow, typically by turning the stem a quarter turn. The essential difference is how the ball is supported and how sealing force is created. Below, we compare their construction, operating characteristics, application fit, sourcing considerations, and the information buyers should confirm before requesting a quotation.

Quick Difference Summary

In a floating ball valve, the ball is not fixed to a lower support. Line pressure can push it toward the downstream seat, helping the seat form a seal. In a trunnion ball valve, the ball is supported by trunnions, so the seat arrangement creates sealing contact around a ball that is held in position.

This construction difference affects operating torque, pressure suitability, size options, and maintenance considerations. Actual performance depends on the valve’s detailed design, materials, pressure and temperature ratings, seat selection, and service conditions. Buyers should compare specific product data sheets rather than relying on the valve type name alone.

How the Two Designs Work

Floating Ball Valve Construction

A floating ball valve has a ball connected to the stem and held between seats, but it does not have trunnion supports that anchor it at the top and bottom. When the valve is closed, upstream pressure can move the ball slightly downstream and press it against the downstream seat. This pressure-assisted seating principle is straightforward and widely used in ball valve designs.

As pressure, valve size, or sealing requirements increase, the force acting on the ball and seats can also increase. That may mean higher operating torque and greater demands on the actuator or operator. Whether a particular floating design is suitable must be checked against its rated conditions and the valve manufacturer’s documentation.

Trunnion Ball Valve Construction

A trunnion ball valve uses upper and lower supports to hold the ball in place as it rotates. The seats move or load against the ball according to the valve design, rather than relying on the ball to shift downstream in the same way as a floating design. This arrangement can reduce the effect of line pressure on the force required to rotate the ball, especially in designs intended for demanding pressure or larger-size applications.

Trunnion construction can involve additional components and design details, including seat-loading arrangements and options for relieving pressure trapped in the body. These features vary by product and are not guaranteed by the term “trunnion” alone. Confirm the proposed valve’s seat design, pressure-relief provisions, operating torque, and maintenance requirements for the intended service.

Feature and Specification Comparison

Both designs can be supplied in different body, ball, stem, and seat materials, and both may be configured for manual or actuated operation. Material choice should account for the fluid, temperature, pressure, corrosion risks, and any project requirements. Do not assume that one construction automatically provides a particular fire-safe, emissions, or other compliance feature; verify applicable documentation for the offered model.

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Application Suitability

When a Floating Ball Valve May Fit

Consider a floating design when the required size, pressure, temperature, and operating torque fall within the manufacturer’s limits, and when its sealing design suits the media and shutoff requirements. It may be appropriate for process, utility, or general industrial isolation duties where the project specification and product data support the selection. A simpler construction can also be useful when buyers want to keep the design and sourcing scope straightforward.

Do not select a floating valve only because it has a lower quoted price. Check the pressure differential across the closed valve, the number of expected operating cycles, the actuator’s available torque, and the consequence of leakage or unplanned maintenance. A valve that is economical at purchase may not be the best fit if it falls outside the required operating envelope.

When a Trunnion Ball Valve May Fit

Consider a trunnion design when the line size or pressure conditions make ball support and operating torque important selection factors. It is commonly evaluated for larger-bore or higher-pressure services, but suitability still depends on the specific model and its rated limits. For critical isolation duties, buyers should also confirm the required leakage criteria, seat arrangement, and any project-specific testing or documentation.

Trunnion valves are not automatically the better option for every demanding application. Their additional design features may not provide useful value in a service that a properly rated floating valve can handle. Compare both options against the same operating conditions and acceptance requirements before finalizing the specification.

Cost, Lead Time, and Sourcing Risk

Price depends on more than valve construction. Size, pressure class, body and trim materials, end connections, seat material, actuation, testing, documentation, and customization can all affect the quotation. A trunnion design may cost more where its support structure or additional features increase manufacturing scope, but the difference should be confirmed using comparable configurations rather than assumed.

Lead time is likewise order-specific and can be affected by material availability, production scheduling, inspection requirements, and delivery terms. For a fair comparison, request quotations for the same nominal size, pressure rating, material, connection type, accessories, and documentation. Also confirm whether quoted delivery timing is an estimate or a committed schedule.

How to Select the Right Valve

1. Define operating conditions. Provide the normal and maximum pressure, temperature range, fluid composition, and expected pressure differential across the closed valve.
2. Confirm size and connections. Specify nominal size, end connection, face-to-face requirements if applicable, and installation constraints. For reference, DN50 is commonly associated with NPS 2, but confirm the actual dimensional standard required by the project.
3. Check materials and sealing needs. Match body, ball, stem, and seat materials to the fluid and service conditions. State leakage expectations and any required fire-safe or emissions-related standards so the supplier can confirm what is available and documented.
4. Review torque and actuation. For automated valves, obtain operating torque data for the specified conditions and confirm actuator sizing, supply, control signals, and fail position where relevant.
5. Compare like-for-like offers. Align scope, technical deviations, inspection, testing, documentation, packaging, and delivery terms before comparing total cost.

When reviewing pressure data across units, make sure the quotation and project specification use the same basis: 1 MPa equals 10 bar. Likewise, 1 inch equals 25.4 mm, but nominal pipe size designations should not be treated as exact measured diameters. Clear units and standards reduce the risk of comparing incompatible offers.

Common Selection Mistakes

• Choosing by size alone: Valve size does not establish suitability without pressure, temperature, media, and torque checks.
• Assuming “trunnion” means higher quality: Construction type is only one selection factor; verify the product’s materials, ratings, design details, and documentation.
• Ignoring differential pressure: The pressure across a closed valve can affect seating and operating requirements, so provide it to the supplier.
• Comparing incomplete quotations: Different seat materials, accessories, testing scope, or documentation can make headline prices misleading.

Key Takeaways and Recommendation

Floating ball valves use pressure-driven ball movement to load the downstream seat and are often considered where size, pressure, and torque requirements are within the design’s limits. Trunnion ball valves support the ball and are often evaluated for larger sizes, higher-pressure conditions, or applications where operating torque is a key concern. The final choice must be validated against the specific valve’s ratings and the actual service conditions.

As a practical next step, prepare a datasheet with size, pressure, temperature, media, pressure differential, connection standard, operating method, and documentation requirements. Ask suppliers to identify any deviations and provide the technical information needed to compare both designs fairly. KAIWEI VALVE can review your project requirements and discuss suitable floating or trunnion ball valve configurations; contact our team with your specifications to request a product recommendation and quotation.

Contact us to discuss your requirements of Trunnion vs. Floating Ball Valves:. Our experienced sales team can help you identify the options that best suit your needs.