What is a floating ball valve?

Floating Ball Valve: Its main characteristic is that the ball is unsupported by an axis and is supported by the valve seats at both ends of the valve body. The valve stem is connected to the ball in a movable manner.The sphere of this type of ball valve is clamped between two valve seats and is in a "floating state". The sphere can freely rotate between the two valve seats through the valve stem with the help of a handle or other driving device. When the flow passage hole of the sphere is aligned with the valve channel hole, the ball valve is in the open state, and the fluid flows smoothly with minimal resistance. When the sphere is rotated 90 degrees, the flow passage hole of the sphere is perpendicular to the valve channel hole, and the ball valve is in the closed state. Under the pressure of the fluid, the sphere is pushed towards the valve outlet (referred to as the valve rear) seat, ensuring tight sealing.

The main advantages of floating ball valves are simple structure, convenient manufacturing, low cost, and reliable operation. The sealing performance of floating ball valves is related to the fluid pressure. Generally, under the same conditions, higher pressure is easier to seal. However, it should be considered whether the seat material can withstand the load transmitted by the sphere, because the force exerted by the fluid pressure on the sphere will be fully transmitted to the seat behind the valve. In addition, for larger-sized floating ball valves, when the pressure is high, the operating torque increases, and the weight of the sphere is also large. The pressure distribution generated by the weight on the sealing surface of the seat is uneven. Generally, the pressure is smaller on the upper half of the channel diameter horizontal plane and larger on the lower half, leading to uneven wear of the seat and leakage. Therefore, floating ball valves are generally suitable for valves with ≤ PN10 and ≤ DN200.

In order to ensure good sealing performance of floating ball valves at lower operating pressures, a certain preload force must be applied between the sphere and the seat. Insufficient preload force cannot guarantee sealing, while excessive preload force will increase friction torque and may cause plastic deformation of the seat material, damaging the sealing performance. For low-pressure ball valves, the thickness of the seal gasket between the center flange can be adjusted to limit the preload force.