Main Difference between floating ball valve and trunnion ball valve

TRUNNION-VALVEBall valve could be divided into two types according to the ball working principles, floating ball valve and trunnion mounted ball valve. So what’s the difference between floating ball valve and trunnion mounted ball valve ? You would be able to choose which to use for your real condition after knowing below details. Let’s go.


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 have 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 turnnion ball valve also don’t have seat injection fitting, such as 2″ 150LB.

Working Priciples

1. The ball of a floating ball 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 push 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 turnnion to fix the ball while floating ball valve not.

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. Tunnion mounted ball valve have double block and bleed function, but a floating type can’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 pretightening 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 not.

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 surported by the spring, so to keep the seat with enough  pretightening force. Even the sealing face wearing out, it still seal good.

The original posted by http://www.teervalve.com/