The floating ball valve is simple in structure, small in size and has good sealing, but the ball of the floating ball valve is floating, Under the medium pressure, the ball can produce certain displacement and press on the seat at the outlet end to ensure the seal of outlet port.The floating ball valve is a single-sided forced seal.So floating ball valve generally can not be used for high pressure and large nominal diameter,Large diameter floating ball valve will cause local deformation of the seat, not conducive to sealing.

The design of floating ball valve should consider whether the seat sealing material can withstand the medium load of the valve ball.This floating ball structure is widely used in low-pressure and medium-pressure ball valves because the ball is subjected to the load of the working medium to the outlet seal ring. In addition, the design should also consider large-diameter ball valve operation requires a large torque.
 
The ball of the fix ball valve is fixed and the valve ball does not move under pressure condition. Fixed ball valves are equipped with a floating seat, the valve seat would create movement under pressure condition,so that the sealing ring pressed on the ball to ensure the seal,at the same time the valve seat will not withstand excessive load. Usually in the upper and lower stem with the bearing sleeve, operation torque is small.Therefore, compared with floating ball valve, fixed ball valve has small torque, small seat deformation and stable sealing performance,the fix the ball valves are suitable for high-pressure and large-diameter valves.