Features and application ranges of valves with different connection methods

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Features and application ranges of valves with different connection methods (1) Threaded connection valves. This type of connection typically involves machining the inlet and outlet ends of the valve into tapered or straight pipe threads, allowing it to be connected to tapered thread fittings or pipelines. Since such connections may have large leakage channels, sealants, sealing tape, or fillers can be used to block these channels. If the material of the valve body is weldable, but there is a large difference in expansion coefficients, or if the operating temperature varies significantly, the threaded connections must be sealed by welding. Valves with threaded connections are mainly those with a nominal diameter of 50 mm or less. If the passage size is too large, it is very difficult to install and seal the connection part. To facilitate the installation and removal of valves with threaded connections, pipe fittings can be used at appropriate locations in the piping system. For valves with a nominal diameter of 50 mm or less, pipe sleeves can be used as pipe fittings, with the threads of the pipe sleeve connecting the two parts together. (2) Flanged valves. Valves with flange connections are easy to install and remove. However, they are heavier than valves with threaded connections, and their price is correspondingly higher. Therefore, it is suitable for pipe connections of various diameters and pressures. However, when the temperature exceeds 350 degrees, as the bolts, gaskets, and flanges become loose, the load on the bolts is significantly reduced, which may lead to leaks in flange connections that are under high stress. (3) Weld the valves together. This type of connection is suitable for various pressures and temperatures, and it is more reliable than flange connections when used under severe conditions. However, valves with welded connections are difficult to disassemble and reinstall, so their use is limited to applications where reliable operation over a long period is required, or in conditions with high stress and temperature. Such as on pipelines in thermal power plants, nuclear energy projects, and ethylene production facilities. Welded valves with a nominal diameter of 50 mm or less typically have welded sockets to receive pipes at the load-bearing end. Since socket welding creates a gap between the socket and the pipe, this gap may be corroded by certain substances, and the vibration of the pipe can cause fatigue at the connection point; therefore, the use of socket welding is subject to certain limitations. In applications with a large nominal diameter, severe operating conditions, and high temperatures, the valve body is often welded using grooved joints. Additionally, strict requirements are placed on the weld seams, necessitating the use of highly skilled welders to carry out this work.