What Is The Difference Between A Floating Ball Valve And A Trunnion Mounted Ball Valve?

ball valve core difference between floating ball valve and fixed ball valve is mainly found in structure design, sealing mechanism, suitable working conditions and performance. The specific analysis is as follows:
1.Structural Design Differences
Floating ball valve
Sphere state: The sphere has no fixed shaft support and can float freely in the valve body. It is connected only by a lower valve stem, while a upperer valve stem conveys only torque.
Sealing method: Medium pressure pushes the ball toward the outlet valve seat, forming a single-sided forced seal (mainly the outlet end).
Structure features: Seat fixed, no additional support structure, compact overall design, small size.
Fixed ball valve
Sphere state: The sphere is fixed to the bearing by the upper and lower stem and cannot be moved but rotates around valve stem axis.
Sealing method: Seat is pressurised by spring or float under medium pressure, ball is tightly held, double-sided sealing is achieved.
Structural characteristics: Bearing and valve seat removable components required, complex structure, thicker valve body to accommodate fixed structure.
2.Comparison of sealing mechanisms
Floating ball valve
Sealing principle: press the ball to the outlet valve seat by dielectric pressure. The greater the media pressure, the better the sealing effect.
Potential problems:
When the pressure is low or not medium, the weight of the sphere itself may prevent the sphere from clinging to the valve seat, causing leakage.
The working medium load of the ball is transferred to the outlet sealing ring and the pressure resistance of the seal ring material needs to be considered.
Applicable scenarios: Low to medium pressure conditions (e.g. ≤ 600), usually ≤NPS 8 in diameter.
Fixed ball valve
Sealing principle: Seat through spring preload or dielectric pressure to press the ball tightly, achieve bidirectional sealing, sealing performance is stable, not affected by dielectric pressure fluctuations.
Advantage functions:
Automatic compensation: When valve seat is worn, the spring automatically adjusts the preload force to maintain the sealing.
Bidirectional sealing: Each valve seat can be sealed independently, and there is no flow restriction during installation.
Safety design: with fire protection, antistatic, automatic pressure relief, discharge of the middle cavity and other functions.
Applicable scenarios: High pressure (up to 2500 class), large diameter (up to NPS 60 class) conditions.
3. Differences in operating performance
Floating ball valve
Turn on and closing torque: Under high pressure, the operating torque is larger and needs to be assisted by a larger actuator or gear device.
Repair features: Simple structure, few parts, easy to repair, but valve seat need to be replaced frequently after seal wear.
Friction problem: During opening and closing closing process the ball and valve seat are always in contact, causing friction and abrasion.
Fixed ball valve
Open and closing torque: The ball is fixed to reduce friction, and opening and closing is easier (especially in large diameter and high pressure conditions).
Maintenance features: Seat adjustable or self-compensating, long maintenance cycle, but high maintenance costs.
Friction optimization: During opening and closing, the ball and valve seat are temporarily separated, reducing friction and prolongs life.
4. Typical application scenarios
Floating ball valve
Strengths: Low cost, simple structure, quick switching, suitable for cost sensitive or fast cutting situations.
Typical uses: water treatment, natural gas, acid-base corrosive medium transport, low and medium pressure pipeline systems.
Fixed ball valve
Strengths: High pressure bearing capacity, reliable sealing, stable operation, suitable for harsh working conditions.
Typical applications: high voltage, large caliber pipeline system in petroleum refining, long pipeline, chemical industry, electricity and other fields.