What Is The Floating Ball in A Ball Valve?

The floating ball is the core opening and closing element of the floating ball valve. It is not positioned on a fixed shaft, but is supported by valve seats at either end. Under the influence of medium pressure, it slightly ``floats' ', automatically touches the seat, achieving sealing. It is the key part of both sealing and on-off control of ball valves.
This ``floating"characteristic directly determines the sealing principle and application range of floating ball valves, which is different from the shaft fixed ball structure of fixed ball valves.
I. Core Structure and operational principles
The structure design and operation logic of the floating sphere revolve around two core functions: sealing and switching control.
Structural characteristics: Floating spheres are hollow or solid spheres (usually hollow to reduce weight and media resistance). It has a perforation that matched the diameter of the pipe. The top of the sphere is connected to the valve stem and the bottom has no fixed support. It is secured by two valve seats on either side of the inlet and exit. Sealing Principle: When the valve is closed, the pressure of the medium in the pipe pushes the sphere toward outlet valve seat, forming a tight squeeze seal between the sphere and the outlet valve seat. The higher the pressure, the tighter the fit, the better the seal.
Switch control: The stem drives the sphere 90°. When the hole in the ball is aligned with the axis of the pipe, the medium passes through smoothly (the valve is fully open). When the opening is perpendicular to the axis of the pipe, the ball blocks the flow of media (the valve is completely closed), opening and closing the pipe.
ii. Key features
The "floating" nature of pontoons is both a source of merit and a manifestation of their limitations:
Strengths:
No fixed axles are required, resulting in simpler structures, fewer parts and lower manufacturing and maintenance costs.
Seal adopts medium pressure automatic compensation, no additional sealing force, high sealing reliability, especially suitable for low and mediumpressure applications.
The ball has low resistance to rotation and is easy to operate. It is suitable for manual or small actuators. Limitations
Limited pressure tolerance: Under the pressure of the medium, the ball presses against the valve seat. Excessive pressure can lead to excessive wear on the seat or spasms in the sphere. Therefore, it applies only to medium and lowpressure pipelines (usually ≤ 4.0 MPa).
Suitable for smaller spheres: When the diameter is too large (usually more than DN200), the size and weight of the spheres increase, greatly increasing the thrust of the media pressure on the spheres, resulting in seal failure or difficulty of 3. Core difference from Fixed Ball Valves
There are great differences in structure and performance between floating ball ball valves and fixed ball valve, which directly affects the application of valve:
Comparison Dimensions: floating ball fixed ball;
Lock method: No fixed shaft, supported by valve seat solely. The ball is positioned horizontally and vertically on a fixed axis and cannot be moved.
Sealing Force: Press the ball against the valve seat under moderate pressure. Active sealing force is applied by a spring or hydraulic mechanism.
Applicable pressure: Low to moderate pressure (≤4.0 MPa)
Applicable Diameter: Small Diameter (usually ≤DN200) Large Diameter (up to DN1000 and above)
Structural Complexity: simple, low cost; Complex, high cost.