Choose a floating ball valve when its size, pressure rating, and operating torque suit the line; choose a trunnion ball valve when the ball needs mechanical support to manage higher loads or larger sizes. The main difference is how each design holds the ball: a floating ball is held between the seats and moves slightly under pressure, while a trunnion ball is anchored by support shafts and the seats move toward it. Neither design is automatically better for every service. To make a reliable choice, compare the actual pressure and temperature conditions, media, valve size, shutoff requirements, and actuation plan.
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Both valve types use a spherical closure element with a bore that opens or blocks flow as the ball turns. They are commonly operated with a quarter-turn movement of approximately 90 degrees, although operating arrangements and stops depend on the valve design. Their shared operating principle does not mean they have the same sealing mechanics or torque requirements.
In a floating design, the ball is not fixed on trunnions. Line pressure can push it toward the downstream seat, helping create a seal. In a trunnion design, the ball is supported at its top and bottom, so it does not float freely; spring-loaded or pressure-responsive seats move against the ball, depending on the design.
| Feature | Floating Ball Valve | Trunnion Ball Valve |
|---|---|---|
| Ball support | Ball is held between the seats and can shift slightly under pressure. | Ball is supported by trunnions and remains positioned while the seats move against it. |
| Sealing action | Pressure can push the ball against the downstream seat. | Seat design provides contact with the supported ball; the exact sealing mechanism varies. |
| Operating torque | Can rise as differential pressure and ball size increase. | Often lower than a comparable floating design under demanding loads, but must be confirmed for the selected valve. |
| Typical selection tendency | Often considered for smaller lines and less demanding pressure conditions. | Often considered for larger lines or higher-pressure duties. |
| Construction and sourcing | May have a simpler construction, depending on the product configuration. | Additional support components and seat mechanisms can affect design, price, and maintenance requirements. |
The difference in ball support affects the forces carried by the seats and the torque needed to operate the valve. In a floating valve, pressure-induced movement of the ball helps load the downstream seat; that same loading can increase friction and operating torque as the service becomes more demanding. In a trunnion valve, the ball is mechanically supported, reducing the need for the seats to carry the ball’s full pressure-driven movement.
These are general design tendencies, not guaranteed performance figures. Seat material, stem and bearing design, pressure differential, temperature, fluid properties, and cycle frequency all influence torque and sealing performance. When specifying an actuated valve, ask the supplier to confirm the required operating torque across the intended operating conditions and to size the actuator with an appropriate engineering margin.
Do not select a valve based on “floating” or “trunnion” alone. Confirm nominal size, pressure class or rating, design temperature, body and trim materials, seat material, bore configuration, end connection, and any applicable project or industry requirements. For example, NPS 2 is commonly designated DN 50; this is a nominal size designation, not a promise of an exact measured bore.
Material selection should reflect the process fluid and operating environment. Stainless steel, carbon steel, and other alloy options may be considered according to corrosion, temperature, pressure, and compatibility requirements, but suitability needs to be checked for the complete wetted assembly, including seats and seals. Likewise, a valve’s stated pressure rating must be reviewed alongside its temperature limits and the applicable product documentation.
A floating ball valve may be appropriate for a smaller line where the specified pressure and temperature fall within the manufacturer’s published limits. Its comparatively straightforward mechanism can make it a practical option for general isolation duties, provided the seat materials and shutoff requirements match the service. It may also be worth considering where initial equipment cost and uncomplicated sourcing are important selection factors.
Do not assume that every small valve should be floating or that a floating valve is unsuitable for all demanding service. Check the actual pressure differential, operating frequency, and torque requirements. If the valve is to be automated, a manual-valve selection that ignores actuator requirements can result in an unsuitable assembly.
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A trunnion design is often a strong candidate for larger-bore or higher-pressure applications, especially when ball support and operating torque are important considerations. It is also commonly evaluated for pipeline isolation and other services where the project specification calls for a supported-ball design. The appropriate choice still depends on the valve’s documented pressure-temperature rating, materials, seats, and end connections.
Trunnion construction may add components and affect purchase price, maintenance planning, and delivery availability. Those differences should be weighed against the operating requirements rather than treated as proof that one design is always more economical over its service life. Ask for the relevant product data and confirm the expected maintenance approach for the selected configuration.
Floating valves may have a lower purchase cost in some size and rating combinations because the design can be less complex. Trunnion valves may require additional support and seat components, which can influence price and availability. However, actual cost and lead time vary by size, pressure class, material, configuration, manufacturing schedule, and inspection or documentation requirements.
For a fair comparison, request quotations for equivalent specifications rather than comparing product names alone. Align the connection type, materials, pressure-temperature requirements, seat construction, operation method, and documentation scope. Confirm whether the quoted lead time includes any project-specific testing, inspection, or customization, and ask the supplier to identify exclusions in writing.
A frequent mistake is treating “high pressure” or “large size” as a complete specification. These terms do not identify the required rating, material, temperature range, or end connection. Another is comparing a floating valve and a trunnion valve with different configurations, then attributing the price difference solely to the support design.
Buyers should also avoid assuming that all trunnion valves have the same seat behavior or that all floating designs provide the same shutoff performance. Ask for the exact model data, clarify the direction and conditions of operation where relevant, and verify that the selected valve meets the project specification. If the line requires automation, include actuator sizing and available power or control requirements in the initial inquiry.
In short, floating ball valves are often a practical choice for smaller, less demanding services, while trunnion ball valves are often favored when the ball needs support under larger or higher-pressure loads. Treat those descriptions as a starting point, not a substitute for checking the design data. The right valve is the one that meets the project’s pressure, temperature, media, shutoff, operation, and sourcing requirements as a complete assembly.
凯维 supports B2B buyers in comparing ball valve configurations against project requirements, including size, materials, pressure rating, end connections, and operating method. To start a technical review, prepare the line conditions, required quantity, target delivery schedule, and any project documentation or inspection needs. We can then help identify whether a floating or trunnion design is the more suitable option and clarify the information needed for a quotation.
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