Quick Answer: Floating vs Trunnion Ball Valve — What’s the Difference?
Floating ball valves use a ball that “floats” between two seat rings — upstream pressure pushes the ball against the downstream seat to seal. They are ideal for smaller sizes (1/2″–12″) and lower pressure classes (Class 150–600). Trunnion mounted ball valves have the ball mechanically anchored by top and bottom trunnions, making them suitable for larger sizes (2″–60″+), higher pressures (Class 600–2500), and critical applications like pipeline and oil & gas.
| Factor | Floating Ball Valve | Trunnion Ball Valve | Source |
| Size Range | 1/2″ – 12″ | 2″ – 60″+ | ✅ Vornet产品页数据 |
| Pressure Rating | Class 150 – 600 | Class 150 – 2500 | ✅ Vornet产品页数据 |
| Ball Support | Free between seats | Fixed trunnions | ✅ 行业标准 |
| Torque | Increases with pressure | Pressure-independent | ✅ 行业标准 |
| Cost | Lower | Higher | ✅ 行业标准 |
| Best For | General industrial, water, chemical | Oil & gas, pipeline, high-pressure | ✅ 行业标准 |
How Ball Valves Work
A ball valve uses a rotating ball with a bore through its center to control flow. When the bore aligns with the pipe, flow passes through; when rotated 90 degrees, the solid part of the ball blocks flow. Ball valves offer quick quarter-turn operation, low torque, and tight shut-off, making them ideal for many industrial applications.
Floating Ball Valves
Design and Operation
In a floating ball valve, the ball is not fixed in position. It is held in place by two seat rings, and upstream pressure pushes the ball against the downstream seat to create a seal. The ball “floats” between the seats, hence the name.
Advantages of Floating Ball Valves
- Simple design: Fewer moving parts, lower cost
- Bidirectional sealing: Seals in both flow directions
- Low operating torque: Easy manual operation
- Compact size: Lighter weight than trunnion valves
- Cost-effective: Lower initial purchase price for smaller sizes
Limitations
- Limited to lower pressure classes (typically Class 150-600)
- Smaller sizes (usually up to 8″-12″)
- Higher operating torque at high pressure due to ball-to-seat loading
- Not ideal for large diameter or high-pressure applications
Trunnion Mounted Ball Valves
Design and Operation
In a trunnion mounted ball valve, the ball is mechanically anchored at the top and bottom by trunnions (shafts). This design absorbs the line pressure load, reducing stress on the seats. The seats are spring-loaded and move independently to press against the ball for sealing.
Advantages of Trunnion Ball Valves
- High pressure capability: Suitable for Class 600 up to Class 2500
- Large sizes: Available from 2″ up to 60″ and beyond
- Low operating torque: Independent of line pressure
- Double block and bleed (DBB): Can isolate pressure from both sides
- Cavity overpressure relief: Self-relieving seat design available
- Fire-safe design: Meets API 607 requirements
Limitations
- Higher initial cost than floating ball valves
- More complex design with additional components
- Heavier weight, especially in large sizes
- May require gear operator for ease of operation
Floating vs Trunnion Ball Valve: Comparison Table
| Feature | Floating Ball Valve | Trunnion Mounted Ball Valve |
|---|---|---|
| Size Range | 1/2″ to 12″ | 2″ to 60″ |
| Pressure Rating | Class 150 – 600 | Class 150 – 2500 |
| Ball Support | Free-floating between seats | Fixed by top and bottom trunnions |
| Sealing Mechanism | Pressure-assisted | Spring-loaded seats |
| Operating Torque | Increases with pressure | Constant, pressure-independent |
| Bidirectional | Yes | Yes (with appropriate seats) |
| DBB Capability | Limited | Yes |
| Relative Cost | Lower | Higher |
| Typical Applications | General industrial, water, chemical | Oil & gas, pipeline, high pressure |
How to Choose Between Floating and Trunnion Ball Valves
Consider these factors when deciding between floating and trunnion ball valves:
- Operating pressure: For Class 600 and above, choose trunnion mounted
- Pipe size: Above 8″-12″, trunnion valves are typically required
- Application criticality: For DBB or fire-safe requirements, choose trunnion
- Budget: For smaller, lower-pressure applications, floating ball valves offer better value
- Actuation: Both types can be automated with pneumatic, electric, or hydraulic actuators
Other Ball Valve Types
In addition to floating and trunnion designs, other ball valve configurations include:
- Fully welded ball valve: One-piece body construction for zero leakage, ideal for buried pipeline service
- Top entry ball valve: Allows in-line maintenance without removing the valve from the pipeline
- Metal seated ball valve: For high-temperature and abrasive service where soft seats cannot be used
- Three-way and multi-port ball valves: For flow diversion and mixing applications
- DBB (Double Block and Bleed) valve: Combines two sealing mechanisms in one valve body
Frequently Asked Questions
What is the main difference between floating and trunnion ball valves?
The main difference is how the ball is supported. In a floating ball valve, the ball moves freely between seats and relies on pressure for sealing. In a trunnion ball valve, the ball is fixed by top and bottom shafts (trunnions), and spring-loaded seats move against the ball for sealing.
When should I use a floating ball valve vs a trunnion ball valve?
Use a floating ball valve for smaller pipe sizes (under 8″-12″), lower pressure applications (Class 150-600), and general industrial use. Use a trunnion ball valve for larger sizes, higher pressures (Class 600 and above), critical oil and gas pipelines, and applications requiring double block and bleed capability.
Are trunnion ball valves fire-safe?
Yes, most trunnion mounted ball valves can be designed to meet API 607 fire-safe requirements. Vornet Valve offers fire-safe trunnion ball valves with secondary metal-to-metal sealing that activates in the event of soft seat destruction during a fire.
Can floating ball valves be used for high-pressure applications?
Floating ball valves are generally limited to Class 600 and below. For higher pressure applications (Class 900, 1500, 2500), a trunnion mounted ball valve is recommended due to its pressure-independent torque and reduced seat stress.
What does DBB (Double Block and Bleed) mean in ball valves?
DBB means the valve can block pressure from both upstream and downstream sides simultaneously, with a bleed port in the cavity to vent trapped pressure. Trunnion mounted ball valves commonly offer DBB capability, making them ideal for isolation applications in oil and gas pipelines.
Vornet Valve Ball Valve Solutions
Vornet Valve offers a complete range of industrial ball valves, including floating ball valves (2-piece and 3-piece designs), trunnion mounted ball valves, fully welded ball valves, top entry ball valves, and metal seated ball valves. All Vornet ball valves are manufactured to API 6D, ASME B16.34, and ISO 9001 standards, with fire-safe design per API 607.
Contact Vornet Valve for ball valve solutions tailored to your specific application requirements. Our engineering team provides technical support, material selection guidance, and competitive pricing.
View our full range of industrial ball valves including floating, trunnion-mounted, and fully welded designs for your specific application.