Advantages and disadvantages of various valves-Ball valve

Author:     Published time:2022-05-14 15:40     Reading times:21    


Ball valve: it is evolved from the plug valve. Its opening and closing part is a ball. The ball rotates 90 ° around the axis of the valve stem to achieve the purpose of opening and closing. The ball valve is mainly used to cut off, distribute and change the medium flow direction on the pipeline. The ball valve designed as V-shaped opening also has good flow regulation function.




advantage:

① It has the lowest flow resistance (actually 0);

② Because it will not get stuck during operation (when there is no lubricant), it can be reliably applied to corrosive media and low boiling point liquids;

③ Complete sealing can be realized in a large pressure and temperature range;

④ It can realize rapid opening and closing, and the opening and closing time of some structures is only 0.05 ~ 0.1s, so as to ensure that it can be used in the automation system of the test-bed. When opening and closing the valve quickly, the operation has no impact;

⑤ The spherical closing part can be automatically positioned at the boundary position;

⑥ The working medium is reliably sealed on both sides;

⑦ When fully open and fully closed, the sealing surface of the ball and 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 With compact structure and light weight, it can be considered as the most reasonable valve structure for low-temperature medium system;

⑨ The valve body is symmetrical, especially the welded valve body structure, which can well bear the stress from the pipeline;

⑩ The closing part can withstand the high pressure difference during closing. (11) the ball valve with fully welded valve body can be directly buried underground, so that the valve internals will not be corroded, and the maximum service life can reach 30 years. It is the most ideal valve for oil and natural gas pipelines.

Disadvantages:

① Because the main valve seat sealing ring material of the ball valve is polytetrafluoroethylene, which is inert to almost all chemicals, and has the comprehensive characteristics of small friction coefficient, stable performance, not easy to aging, wide temperature application range and excellent sealing performance. However, the physical characteristics of PTFE, including high expansion coefficient, sensitivity to cold flow and poor thermal conductivity, require that the design of valve seat seal must focus on these characteristics. Therefore, when the sealing material hardens, the reliability of the seal is damaged. Moreover, the temperature resistance grade of polytetrafluoroethylene is low and can only be used under the condition of less than 180 ℃. Beyond this temperature, the sealing material will age. When considering long-term use, it is generally not used at 120 ℃.

② Its regulation performance is worse than that of the stop valve, especially the pneumatic valve (or electric valve).

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