The ball valve is evolved from the plug valve. Its open-close disc is a ball, By rotating the ball with 90° around the axis of the stem to achieve the purpose of opening and closing. The ball valve is mainly used for cutting off, distributing, and changing the flow direction of the medium.
① With the lowest flow resistance (actually 0)
② Can be used reliably in corrosive media and low boiling point liquids because it will not get stuck when working.
③ In a larger range of pressure and temperature can be completely sealed.
④ Rapid opening and closing can be realized, and the opening and closing time of some structures is only 0.05~0.1s, so as to ensure it can be used in the automation system of the test bench. When the valve is opened and closed quickly, the operation has no impact;
⑤ The spherical closure can be automatically positioned at the boundary position.
⑥ The medium is sealed reliably on both sides
⑦ When fully open and fully closed, the sealing surface of the ball and the valve seat is isolated from the medium, so the medium passing through the valve at high speed will not cause erosion of the sealing surface.
⑧ Compact structure, lightweight, it can be considered as the most reasonable valve structure for the low-temperature medium system;
⑨ Valve body symmetry, especially welded valve body structure, can well withstand the stress from the pipeline;
⑩ The closure can withstand the high-pressure difference during the closing
⑪ All-welded type ball valve can be directly buried in the ground
so that the valve internal parts are not corroded, and the maximum service life
can reach 30 years, is the best choice for oil, and natural gas pipelines.
Disadvantages of Ball Valve:
① As the main material of the sealing seat of the ball valve is Teflon. It is inert to almost all chemical substances and has a small coefficient of friction, stable performance, not easy to aging, wide temperature range of application, and good sealing performance of the comprehensive characteristics. However, the physical properties of Teflon, including a high coefficient of expansion, sensitivity to cold flow, and poor thermal conductivity, which require that seat seals be designed around these properties. Therefore, when the sealing material hardens, the reliability of the seal is damaged. In addition, Teflon has a lower temperature resistance grade and can only be used when it is less than 180℃. Beyond this temperature, the sealing material ages. Considering the case for long-term use, it is generally only used below 120℃.
② Its regulating performance compared to the globe valve is a little worse, especially the pneumatic valve (or electric valve).