The core differences between floating ball valves and fixed ball valves are mainly reflected in four aspects: structural design, sealing principle, performance characteristics and application scenarios. The specific differences are as follows:
1. Structural design differences
Floating ball valve
Single stem floating structure: The ball is only connected by a single-side valve stem, not completely fixed, and can move slightly along the medium flow direction in the valve body.
No lower support shaft: There is no fixed support at the bottom of the ball, and the medium pressure is relied on to push the ball to the outlet valve seat.
Fixed ball valve
Dual stem fixed structure: The ball is rigidly connected to the valve body through the upper and lower valve stems, and cannot be displaced, but can only rotate.
Bearing support: The upper and lower valve stems are equipped with thrust bearings or sliding bearings to reduce friction resistance39.
2. Differences in sealing principles
Floating ball valve
One-way dynamic seal: When closed, the medium pressure pushes the ball to move toward the outlet valve seat, forming a one-sided forced seal (outlet end seal).
Low pressure depends on preload: When there is no medium pressure, the valve seat preload is used for sealing, and low pressure conditions are prone to leakage.
Fixed ball valve Two-way active sealing: The valve seat is always close to the ball through the spring preload, and the medium pressure further pushes the valve seat to enhance the seal (two-way sealing).
Automatic wear compensation: The valve seat spring can automatically compensate for the wear of the sealing surface and maintain long-term sealing.
3. Performance and application comparison Operating torque Under high pressure, the floating ball valve is pressed against the valve seat due to the pressure of the ball, and the operating torque increases sharply, which is easy to get stuck. Fixed ball valves are supported by bearings and symmetrically stressed, with stable torque, suitable for high-pressure and large-diameter operations (DN≥200 or pressure≥Class 600). Pressure resistance and caliber adaptability Floating ball valves are limited to medium and low pressure (≤PN40) and small and medium caliber (DN≤200) scenarios, and high pressure is easy to crush the valve seat.
Fixed ball valves are suitable for high-pressure (Class 600 and above), ultra-low temperature (-196℃) and large-diameter (DN≥200) pipelines.
Media adaptability
Floating ball valves are suitable for clean media (such as water and air), and media containing particles are prone to damage the sealing surface.
The valve seat of the fixed ball valve can be designed with a scraping structure to withstand media containing solid particles, high viscosity or corrosive media.
4. Typical application scenarios
Floating ball valve: low cost, widely used in non-harsh working conditions such as low-pressure clean water, air conditioning systems, general industrial pipelines, etc.
Fixed ball valve: fields with high safety requirements such as long-distance oil and gas pipelines, chemical high-pressure reaction devices, and LNG ultra-low temperature systems.
