In terms of valve structure, we could divide ball valve into floating ball valve and trunnion-mounted ball valve.

The working principle for floating ball valve:
The ball inside the valve body is floating, since it does not have lower stem to fix and support the ball. Under medium pressure, the medium pushes the ball, and the ball can generate a certain displacement and press on the sealing surface at the outlet. The floating ball can only ensure outlet sealing but not for inlet sealing. The floating ball valve is usually suitable for small size valves, better less than 6 inch.

The working principle for trunnion ball valve:
In contrast, the trunnion ball is fixed and supported by seat support as well as the upper & lower stem. Under the medium pressure, the valve seat will move, so that the sealing ring is pressed against the ball to ensure the seal. When the fixed ball valve is working, the pressure of the fluid before the valve is transmitted only to the bearing and the valve stem, and does not cause pressure on the valve seat, so the trunnion ball valve has small torque value, small deformation of the valve seat, stable sealing performance and long service life. It can handle higher working pressure and larger sizes.

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