Classification and function of ball valves

Classification and function of ball valves
Ball valves and plug valves belong to the same type of valve, which uses a ball core with a circular through-hole as the opening and closing element. The ball core is driven by the valve stem and rotates 90 ° around the axis of the valve stem to achieve the opening and closing action of the valve.

Ball valves are mainly used in pipelines to cut off, distribute, and change the direction of medium flow. Ball valves have the advantages of simple structure, reliable sealing, rapid opening and closing, wide applicability (can be used for various pipelines of different sizes and high and low pressures), and easy maintenance and operation.
With the improvement and development of China’s industrial level, the application of ball valves is becoming more and more widespread. Some special applications such as large-diameter and high-pressure ball valves have achieved continuous breakthroughs and localization, providing huge support for the application of special industries such as West East Gas Transmission, natural gas transmission, and nuclear power in China.
Classification of ball valves
1、 According to the structural form
Ball valves can be divided into floating ball valves, fixed ball valves, and elastic ball valves according to their structural forms. Below are brief introductions for everyone:
1. Floating ball
The ball of a floating ball valve is floating, and under the pressure of the medium, the ball can produce a certain displacement and press tightly against the sealing surface at the outlet end, ensuring the sealing performance at the outlet end.
Floating ball valves have advantages such as simple structure, good sealing performance, and low price. However, since the load of the working medium borne by the sphere is all transmitted to the outlet sealing ring, it is necessary to consider whether the sealing ring material can withstand the working load of the sphere medium. This type of ball valve structure is currently widely used in applications with medium/low pressure and small diameter.
2. Fixed ball
The ball of a fixed ball valve is fixed and will not move when subjected to medium pressure. Fixed ball valves are equipped with floating seats, which move when subjected to medium pressure, causing the sealing ring to press tightly against the ball to ensure sealing performance. Therefore, fixed ball valves are usually equipped with bearings on the upper and lower shafts of the ball, with low operating torque, especially suitable for high-pressure and large-diameter valves.
In order to increase the operating torque and sealing reliability of the Zang Shaoqiu valve, oil sealed ball valves have emerged in recent years, which inject specially formulated lubricating oil between the sealing surfaces to form a layer of oil film. This not only enhances the sealing performance but also reduces the operating torque, making it more suitable for high-pressure large-diameter ball valves.
3. Elastic ball
The ball of an elastic ball valve is elastic. The ball and valve seat sealing ring are both made of metal materials, and the sealing pressure ratio is very high. Relying on the pressure of the medium itself cannot meet the sealing requirements, and external force must be applied. This type of valve is suitable for high temperature and high pressure media.
An elastic sphere is formed by creating an elastic groove at the lower end of its inner wall to obtain elasticity. When closing the channel, use the wedge-shaped head of the valve stem to expand the ball and press it against the valve seat to achieve sealing. Release the wedge-shaped head before rotating the sphere, and the sphere will return to its original shape, creating a small gap between the sphere and the valve seat, which can reduce friction and operating torque on the sealing surface.
2、 According to the form of the ball core
Ball valves can be divided into two types based on the form of the ball core: “V” – shaped ball valves and “O” – shaped ball valves.
The “O” type ball valve is mainly used for the on/off of media, achieving the circulation and cutoff of media through the opening and closing of the ball core.
The “V” type ball valve is mainly used to regulate the flow rate of the medium, playing a role similar to a regulating valve.
Attention: When the medium contains solid particles, is prone to crystallization, etc., using a ball valve can easily cause blockage and prevent the valve from operating. At this point, it is strongly recommended to use the multifunctional regulating valve produced by Chongqing Puhui Si Valve as a substitute. The multifunctional regulating valve has good anti blocking performance.
3、 According to the sealing form
Ball valves can be divided into two categories based on their sealing forms: hard sealed ball valves and soft sealed ball valves.
Hard sealed ball valves refer to valves with metal hard sealing materials for both the valve core and seat. Therefore, hard sealed ball valves are suitable for special working conditions such as large pressure differentials, high temperatures, and wear resistance. However, they are relatively expensive, usually 2-3 times more expensive than ordinary soft sealed ball valves, or even higher.
Soft sealed ball valves generally refer to ball valves with valve seats made of non-metallic materials such as PTFE and ball cores made of metallic materials. Soft sealed ball valves are widely used in medium and low-pressure control applications due to their advantages such as low cost and minimal leakage (usually zero leakage).