Main Difference between floating ball valve and trunnion ball valve

Appearance.

1. If you see a ball valve with a down trunnion, it must be trunnion mounted ball valve, because floating ball valve don’t have.

2. When a ball valve has seat injection fitting, there’s no doubt it’s a trunnion ball valve. But you can’t say it must be a floating ball valve, because very small size trunnion ball valve also doesn’t have seat injection fitting, such as 2″ 150LB.

Working Principles.

1. The ball of a floating ball is movable, it moves slightly after the medium give pressure to it, then the ball touched closely with the seat to seal. But in a trunnion mounted ball valve, the ball is fixed, don’t move. The medium pushes the seat move and closely touched with the ball, that’s the way of sealing.

Design and Usage.

1. Trunnion mounted ball valve have a lower trunnion to fix the ball while floating ball valve don’t.

2. Floating ball valve is usually for small size up to 10″ and low pressure, while trunnion type reaches max 60″, pressure up to 2500LB.

3. Trunnion mounted ball valve has double block and bleed function, but a floating type don’t. Trunnion ball valve could block the medium from both upstream and downstream, it’s totally bidirectional design. When the pressure in the valve cavity is higher than the retightening force, it will push the seat move to relief the pressure, so to keep safe

4. The torque of a trunnion ball valve is smaller than a same size and pressure floating ball valve.

5. Trunnion ball valve have emergency seat injection fitting for size bigger than 4″ while floating ball valve don’t.

6. The sealing of trunnion ball valve is much more reliable than floating type, the seat was inserted into a steel retainer, and the retainer supported by the spring, so to keep the seat with enough re-tightening force. Even the sealing face wearing out, it still seals well.