Trunnion Ball Valve VS Floating Ball Valve

Trunnion Mounted Ball Valve – A trunnion mounted ball valve has additional mechanical anchoring at the top and bottom on the ball. Moreover, this design allows for reduction in valve torque as the ball is supported in two places. The trunnion mounted stem absorbs the thrust from the line pressure, preventing excess friction between the ball and seats, so even at full rated working pressure operating torque remains low.

Floating Ball Valve– A floating ball valve is not held in place by a trunnion, and instead is attached only to the stem. This sometimes causes the ball to float slightly downstream. However, when this happens, the ball presses against the seat, creating a positive seal.



Trunnion Mounted Ball Valve is suitable for larger and higher pressure flow. The applicable size and pressure ratings as below:

ANSI Class 2500  1-12” and above

ANSI Class 1500  2” and above

ANSI Class 900   2” and above

ANSI Class 600   3” and above

ANSI Class 300   4” and above

ANSI Class 150   4” and above


Floating Ball Valve is suitable for small sizes and pressure ratings as below:

ANSI Class 1500  2” and smaller

ANSI Class 900   3” and smaller

ANSI Class 600   3” and smaller

ANSI Class 300   4” and smaller

ANSI Class 150   6” and smaller



Trunnion Mounted Ball Valve is usually designed as DBB. Both seat can block the flow from upstream and downstream seperately, if the flow is caught in the valve ball, the pressure in the ball rises at 1.33 times of the valve design pressure, the flow will be self-relieving to the downstream.

For Floating Ball Valve, the ball is floating slightly when it is under the pressure as required, generally speaking no pressure is caught in the valve ball, also both seats cannot block the flow at the same time.

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