Connection of pipeline valves

This post was last edited by jfwzf on 2018-8-2 at 12:45. Ignoring the routine maintenance of the valve, welding is used. Valves are connected using flanges, which facilitates disassembly and maintenance.

There are three main connection methods for valves: welding, threading, and flanging. For valves with large nominal diameters, under severe operating conditions and at high temperatures, the valve body is often welded using grooved joints. Additionally, strict requirements are placed on the weld seams; therefore, skilled welders must be employed to carry out this work. Welded valves with a nominal diameter of 50 mm or less usually 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; as a result, the use of socket welding is subject to certain limitations. Welded joints are suitable for various pressures and temperatures, and they are more reliable than flanged joints 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 the pipelines of thermal power plants, nuclear energy projects, and ethylene production facilities. 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. Threaded connections typically involve 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. 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 joints, with the threads of the pipe sleeve connecting the two parts together. Valves with flange connections are easy to install and remove. However, they are heavier than valves with threaded connections, and their price is also higher; as a result, they are suitable for connecting pipes of various diameters and pressures. When the temperature exceeds 350 degrees, as the bolts, gaskets, and flanges become loose, the load on the bolts is significantly reduced, which can lead to leaks in flange connections that are under high stress. :victory::victory::victory: