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Created on 09.20

Difference Between Floating Ball Valves and Trunnion Ball Valves

Difference Between Floating Ball Valves and Trunnion Ball Valves

September 20, 2026
The difference between floating ball valves and trunnion ball valves lies in the way the ball is supported within the valve body. A floating ball valve has a ball that moves freely and "floats" when pressure is applied. A trunnion-mounted ball valve, on the other hand, features a ball that is mechanically fixed in place. This structural difference determines which valve can handle higher pressures, requires less operating force, and performs better in large-diameter applications.

What Is a Floating Ball Valve?

In a floating ball valve design, the ball has no mechanical anchoring system and relies entirely on fluid pressure for sealing. When pressure increases, it pushes the ball against the downstream seat, forming a tight seal. This pressure-assisted mechanism means that higher system pressures can actually improve sealing performance.
Key features: simple construction with fewer parts, reducing manufacturing costs; improved self-sealing performance because pressure forces the ball against the seat; cost 30-50% lower than equivalent trunnion valve designs; compact, lightweight design that makes installation easy in tight spaces. Most floating ball valves perform best in applications with diameters up to 6 inches and pressure ratings up to 1,480 PSI (Class 600).

What Is a Trunnion Ball Valve?

A trunnion ball valve features a ball that is mechanically fixed at the top and bottom positions by shafts (trunnions). Even under extreme pressure conditions, this design prevents the ball from moving within the valve body. Spring-loaded seats move toward the fixed ball to form a seal, ensuring consistent performance regardless of pressure variations. The mechanical support system distributes pressure loads across the trunnion bearings rather than concentrating force on the seats and stem.
Key features: the ball remains in a fixed position, eliminating pressure-induced movement; operating torque remains consistent across all pressure ranges; can withstand pressures up to 6,000 PSI in demanding applications; suitable for large sizes from 6 to 48 inches. Trunnion valves can withstand pressures up to 6,170 PSI (Class 2500) and sizes up to 48 inches or larger.

Floating Ball Valves vs. Trunnion Ball Valves: Technical Comparison

Floating ball valves and trunnion ball valves differ in several key performance aspects, and these differences directly affect their suitability for specific applications. Let's take a closer look.
Pressure Performance Analysis: Pressure handling represents a fundamental difference between these valve types. As pressure rises, the torque of a floating ball valve increases exponentially, making operation increasingly difficult above 800 PSI. At 1,000 PSI, a 4-inch floating valve requires 300-400% more operating torque than at atmospheric pressure. Due to mechanical load distribution, trunnion ball valves maintain consistent torque requirements across the entire pressure range. This consistency enables reliable automation and predictable performance in high-pressure applications.

Size and Flow Analysis

In practical applications, size capability clearly distinguishes floating designs from trunnion designs. Due to the weight of the ball and hydraulic forces, floating designs become impractical above 6 inches. Trunnion valves effectively handle large diameters through their mechanical support system.

Actuator Requirements and Energy Efficiency

There are significant differences in actuator sizing and energy consumption between floating and trunnion designs. These differences directly affect automation costs and long-term operating expenses. Electric actuators for trunnion valves require 30-50% less capacity, reducing initial costs and energy consumption. Pneumatic systems benefit from lower supply pressure requirements and reduced air consumption.

Maintenance and Service Life Comparison

Maintenance requirements and service intervals vary greatly between the two valve types. The trunnion design allows seat replacement without removing the valve from the pipeline, reducing maintenance downtime by 60-80%. Despite higher individual service costs, the extended service life of trunnion valves typically reduces total maintenance costs.

Valve Selection Guide: Making the Right Choice

A comprehensive valve selection guide must consider multiple factors, including pressure, size, automation requirements, and lifecycle costs. System pressure is the primary selection criterion, with floating designs being optimal below 1,000 PSI and trunnion designs required above 1,500 PSI. Valve size is another clear decision point, as floating designs above 6 inches are impractical due to operating torque requirements.
Pressure-Size Selection Matrix:
Small sizes (1-3 inches): For cost efficiency, floating valves are recommended for pressures up to 2,500 PSI; trunnion valves are advantageous for automation compatibility above 600 PSI.
Medium sizes (4-6 inches): With adequate actuators, floating valves can handle pressures up to 1,480 PSI; trunnion valves are preferred above 800 PSI or for frequent operation.
Large sizes (8+ inches): Trunnion valves are required for all pressure applications; floating designs are not recommended due to operating limitations.

Automation Considerations

In automation applications, actuator sizing requirements strongly favor trunnion designs. An electric actuator for a 4-inch floating valve at 600 PSI requires at least 500 inch-pounds of capacity, while an equivalent trunnion design requires only 200 inch-pounds. Pneumatic actuators offer similar advantages, with trunnion valves requiring 80-100 PSI supply pressure, while floating designs under pressure require 120+ PSI. This efficiency means smaller actuators, lower energy consumption, and longer equipment service life.

Cost Analysis and Return on Investment

Compared to equivalent trunnion designs, floating ball valves typically have an initial purchase cost that is 30-50% higher. However, when operational efficiency and maintenance costs are included, total cost of ownership calculations lead to different conclusions.
Lifecycle cost factors: actuator size and energy consumption, maintenance frequency and complexity, service life expectations, downtime costs, and safety considerations. For high-pressure applications, trunnion valves typically achieve cost parity within 3-4 years through reduced maintenance and improved operating efficiency. Automation applications tend to favor trunnion designs due to smaller actuator requirements and consistent torque characteristics.

Industry Standards and Compliance

Both floating ball valves and trunnion ball valves must comply with strict industry safety and performance standards. API-609 and API 6D certification require a 15-minute pressure test at 1.5 times the rated pressure (shell test) and a pressure test at 1.1 times the rated pressure on the seat.
Fire testing in accordance with API 607 places the valve at 1,400°F for 30 minutes, with a maximum allowable leakage of 5 ml per minute per inch of diameter. Fugitive emission compliance according to API 622 limits methane leakage to below 100 ppm over 1,500 thermal cycles. Cycle testing requirements specify a minimum of 5,500 cycles for floating designs and 10,000 cycles for trunnion valves at full pressure rating.

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