The floating ball valve drives the displacement of the ball through the medium pressure to achieve sealing. Its core working principle and structural features are as follows:
1. Core working principle
Floating ball structure:
The ball is connected to the actuator only through the valve stem, without upper and lower shaft fixation, and can float in the valve cavity.
Sealing mechanism:
Closed state: The medium pressure pushes the ball to move toward the outlet valve seat, squeezing the sealing ring to form a dynamic seal;
Pressure dependence: The sealing effect increases with the increase of medium pressure (depending on the valve seat preload at low pressure).
Opening and closing action:
The valve stem rotates 90° to drive the ball to rotate, so that the ball channel is parallel to the pipeline (fully open) or vertical (fully closed).
2. Key structural design
Valve seat sealing system:
Dual valve seat design (inlet/outlet end), wrapping the ball to achieve two-way sealing;
The sealing material can be PTFE (corrosion resistant), metal hard seal (high temperature resistant) or composite material.
Safety additional structure:
Anti-static device: A conductive spring is set between the ball and the valve stem to conduct friction static electricity;
Fireproof structure: After the soft seal is burned, the metal sealing surface is sealed in an emergency;
Valve stem anti-flying design: Prevent abnormal pressure from pushing out the valve stem.
Locking device: The fully open/fully closed position can be locked to avoid misoperation.
3. Performance characteristics and limitations
| Advantages | Limitations |
|---|---|
| Simple structure and low maintenance cost | Large diameter (DN＞200) valve seat is easy to be damaged under high pressure |
| Small fluid resistance (full bore design) | Weak sealing performance under low pressure conditions |
| Quick opening and closing (90° rotation is enough) | The friction between the ball and the valve seat is large, and the service life is limited |
4. Typical application scenarios
General industrial media: medium and low pressure pipelines such as water, oil, and gas (common pressure ≤ PN40);
Special working conditions:
Natural gas pipelines containing hydrogen sulfide (anti-corrosion valve seats are required);
Oil tank drainage system (floating ball check valve to prevent oil spills).
Prohibited scenarios: working conditions with ultra-large diameter (DN＞300), ultra-high pressure (PN＞64), or frequent flow adjustment.
