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What is the difference between Floating Ball Valve and Trunnion-Mounted Ball Valve?

March 29, 2025

Floating Ball Valve vs. Trunnion-Mounted Ball Valve: Key Differences

While both floating and trunnion-mounted ball valves are types of ball valves, they differ significantly in design, sealing mechanisms, and applications. Below is a detailed comparison to clarify their distinctions:

1. Core Design and Sealing Mechanism

Floating Ball Valve:
- The ball is not mechanically anchored and "floats" between two valve seats.
- Sealing: Fluid pressure pushes the ball against the downstream seat, creating a tight seal.
- Best for: Low-to-medium pressure applications (typically up to 1,000 psi).
Trunnion-Mounted Ball Valve:
- The ball is fixed in place by trunnions (shafts) at the top and bottom.
- Sealing: Uses spring-loaded or mechanically preloaded seats to seal against the ball, independent of fluid pressure.
- Best for: High-pressure (up to 7,250 psi) or large-diameter pipelines (e.g., oil and gas transmission lines).

2. Structural Differences

Feature	Floating Ball Valve	Trunnion-Mounted Ball Valve
Ball Support	No mechanical anchors; relies on fluid pressure	Fixed by trunnions and bearings
Seat Design	Soft seats (e.g., PTFE) or metal-to-metal seals	Spring-energized seats with backup rings
Torque Requirement	Higher torque due to friction from fluid pressure	Lower torque due to reduced seat friction
Size Range	Smaller diameters (2"–12")	Larger diameters (up to 60"+)

3. Performance and Applications

Floating Ball Valve:
- Advantages:
  - Compact, lightweight design.
  - Lower cost for small-scale systems.
  - Suitable for general-purpose use in water, oil, and gas.
- Applications:
  - Residential plumbing, HVAC systems.
  - Low-pressure chemical processing.
  - Fuel dispensing systems.
Trunnion-Mounted Ball Valve:
- Advantages:
  - Handles extreme pressures and temperatures.
  - Minimal wear on seats due to reduced friction.
  - Bidirectional sealing capability.
- Applications:
  - High-pressure oil and gas pipelines (e.g., API 6D-certified valves).
  - Cryogenic LNG storage (-196°C).
  - Large-scale refinery and petrochemical plants.

4. Maintenance and Durability

Floating Ball Valve:
- Maintenance: Seats may wear faster under high pressure; periodic replacement required.
- Lifespan: Shorter in abrasive media (e.g., slurries).
Trunnion-Mounted Ball Valve:
- Maintenance: Long-lasting seats due to spring-assisted sealing; often includes a grease injection system for lubrication.
- Lifespan: Superior in harsh environments (high pressure, corrosive fluids).

5. Cost Comparison

Factor	Floating Ball Valve	Trunnion-Mounted Ball Valve
Initial Cost	Lower	Higher
Operational Cost	Higher maintenance frequency	Lower maintenance needs
Total Cost of Ownership	Cost-effective for small systems	Economical for large-scale, high-pressure systems

Summary: Which to Choose?

Opt for a Floating Ball Valve if:
- You need a compact, affordable solution for low-to-medium pressure systems.
- Space or weight constraints exist (e.g., residential or light industrial use).
Choose a Trunnion-Mounted Ball Valve if:
- Your application involves high pressure, large diameters, or abrasive/corrosive media.
- Long-term reliability and minimal downtime are critical (e.g., oil and gas pipelines).