Ball valves can be classified by structure as follows:
1. Floating Ball Valve
The ball in this type of valve floats. Under the pressure of the medium, the ball can move to a certain extent and press tightly against the sealing surface at the outlet end, ensuring a seal at the outlet.
Floating ball valves have a simple structure and good sealing performance. However, the load of the working medium on the ball is entirely transferred to the outlet sealing ring. Therefore, it is necessary to consider whether the sealing ring material can withstand the working load of the medium on the ball. This structure is widely used in medium and low-pressure ball valves.
2. Fixed Ball Valve
The ball in this type of valve is fixed and does not move under pressure. Fixed ball valves all have a floating seat. Under the pressure of the medium, the seat moves, pressing the sealing ring tightly against the ball to ensure a seal. Bearings are usually installed on the upper and lower shafts of the ball, resulting in low operating torque. This type of valve is suitable for high-pressure and large-diameter valves. To reduce the operating torque of ball valves and increase sealing reliability, oil-sealed ball valves have emerged in recent years. These valves inject a special lubricating oil between the sealing surfaces to form an oil film, enhancing sealing performance and reducing operating torque. This makes them more suitable for high-pressure, large-diameter ball valves.
3. Resilient Ball Valve
The ball in this type of ball valve is elastic. Both the ball and the valve seat sealing ring are made of metal. The sealing pressure is very high, and the pressure of the medium itself is insufficient to achieve a seal; external force must be applied. This type of valve is suitable for high-temperature, high-pressure media.
The elastic ball is achieved by creating an elastic groove at the lower end of the inner wall of the ball. When the passage is closed, the wedge-shaped head of the valve stem expands the ball and presses it against the valve seat to achieve a seal. Before rotating the ball, the wedge-shaped head is released, and the ball returns to its original shape, creating a small gap between the ball and the valve seat, reducing friction on the sealing surfaces and operating torque.
