1. Floating Ball Valve
In this type of valve, the ball is not fixed in place; under the pressure of the medium, it undergoes a slight displacement and presses firmly against the sealing surface at the outlet end, ensuring a tight seal. While the structure is simple and sealing performance is excellent, the entire load exerted by the working medium on the ball is transferred to the outlet sealing ring; therefore, the material of the sealing ring must be capable of withstanding this load. This structural design is widely used for low- and medium-pressure ball valves.
2. Trunnion-Mounted Ball Valve
The ball in this valve is fixed and does not move under pressure. Instead, the valve features floating seats; under medium pressure, the seats shift to press the sealing rings against the ball, ensuring a tight seal. Bearings are typically installed on the upper and lower stems supporting the ball, resulting in low operating torque; this design is suitable for high-pressure, large-diameter valves. To further reduce operating torque and enhance sealing reliability, oil-sealed ball valves have been developed; these inject a special lubricant between the sealing surfaces to form an oil film, which improves sealing performance and reduces torque, making them particularly suitable for high-pressure, large-diameter applications.
3. Elastic Ball Valve
This valve features an elastic ball. Both the ball and the seat sealing rings are made of metal, resulting in high sealing contact pressure; since the pressure of the medium alone is insufficient to achieve the required seal, external force must be applied. These valves are suitable for high-temperature, high-pressure media. Elasticity is achieved by cutting a slot into the lower section of the ball's inner wall. When closing the valve, the wedge-shaped head of the stem expands the ball, pressing it tightly against the seat to create a seal. Before rotating the ball, the wedge-shaped head is released, allowing the ball to return to its original shape and creating a small gap between the ball and the seat, which reduces friction on the sealing surfaces and lowers operating torque.
