Ball valve and the working principle of the same plug, are by rotating the valve plug to open or close the valve. The valve spool is a perforated ball, when the center of the hole and the valve inlet and outlet of the central axis coincide, the valve open; when rotating the ball 90 °, so that the central axis of the hole and the valve inlet and outlet of the central axis When vertical, the valve closes.
(1) floating ball valve. The sphere has a certain amount of float, which can be displaced toward the outlet end and press the seal under media pressure. This ball valve structure is simple, good sealing. But due to the ball floating, the media pressure will be passed to the sealing ring, so that the burden of heavy seals; taking into account the bearing capacity of the restrictions, but also take into account the large ball valve, such as the use of this structure, is bound to operate effort, Medium and low pressure small diameter valves.
(2) fixed ball valve. The sphere is fixed and can not move. Usually on the lower bearing with a rolling bearing or sliding bearings, opening and closing lighter. This structure is suitable for the production of high pressure large diameter valves.
Seat seals are made of polytetrafluoroethylene, because of its small friction factor, excellent corrosion resistance, wide temperature range. Polychlorotrifluoroethylene can also be used, which is slightly worse than the former corrosion resistance, but high mechanical strength. Rubber sealing performance is very good, but the pressure, poor temperature performance, only for low temperature low-pressure pipeline. Large ball valve, can be made of mechanical transmission, but also by the power, hydraulic, power to operate. Ball valve and plug valve, can be made of right angle, three links, four links and other forms.
① The biggest feature of the ball valve is in many types of valves in the fluid resistance of the smallest flow characteristics of the best.
② for the requirements of fast opening and closing of the occasion generally use the ball valve.
③ compared with the butterfly valve, its weight is larger, the structure size is relatively large, it should not be used for too much diameter pipe.
④ ball valve and plug valve compared to the switch light, relatively small size, it can be made into a large diameter valve.
⑤ ball valve seal is reliable, simple structure, easy maintenance, sealing surface and the ball is often in a closed state, not easily eroded by the media.
⑥ with the butterfly valve, long-term impact it can not be applied in the petrochemical production plant is the problem of thermal expansion or wear will cause a tight seal. Soft seal ball valve has better sealing performance, but when it is used for flammable, explosive media pipeline, still need to fire safety test and anti-static test. Therefore, the petrochemical production unit on the ball valve application is not much. In recent years, many ball valve manufacturers have developed a number of new structure of the ball valve, such as the ball valve, eccentric ball valve, etc., some ball valve seat will be set into metal elastic seat, so that in the case of thermal expansion and wear is still good seal. Therefore, these ball valves have been used in the petrochemical production plant.
⑦ through the ball valve for cutting off the media, three-way ball valve can change the direction of the media flow or distribution. Articles from the network, by the Shanghai Zize pump to adjust the ball valve opening and closing quickly, easy to achieve emergency cut off the accident. As the throttling may cause damage to the seal or the ball, generally do not use ball valve throttling. Full channel ball valve is not suitable for regulating flow.
The ball valve has a long service life and maintenance-free period, will depend on the following factors: normal working conditions, maintain a harmonious temperature / pressure ratio, and reasonable corrosion data.