1. Floating Ball Valve
In this type of valve, the ball is "floating"-meaning it is not mechanically fixed in place. Under the pressure of the medium, the ball shifts slightly and presses firmly against the sealing surface at the outlet end, ensuring a tight seal.
Floating ball valves feature a simple structure and good sealing performance; however, the entire load exerted by the working medium on the ball is transferred to the outlet sealing ring. Consequently, the material of the sealing ring must be capable of withstanding these operational loads. This structural design is widely used for low- and medium-pressure ball valves.
2. Trunnion-Mounted Ball Valve
In this design, the ball is fixed in place and does not shift under pressure. Trunnion-mounted ball valves utilize floating seats; under medium pressure, the seat moves to press the sealing ring firmly against the ball, ensuring a tight seal. Bearings are typically installed on the upper and lower stems (trunnions) of the ball, resulting in low operating torque; this design is suitable for high-pressure and large-diameter valves.
To reduce operating torque and enhance sealing reliability, lubricated-seat (or "oil-seal") ball valves have been developed in recent years. Special lubricant is injected between the sealing surfaces to form an oil film, which simultaneously improves sealing performance and reduces operating torque, making them particularly suitable for high-pressure, large-diameter applications.
3. Elastic Ball Valve
In this type, the ball itself is elastic. Both the ball and the seat sealing rings are constructed from metal materials. Because the required sealing contact pressure is extremely high, the pressure of the medium alone is insufficient to achieve a seal; therefore, external force must be applied. These valves are suitable for high-temperature and high-pressure media.