Features and application scope of valves with different connection methods

1. Threaded valve. This connection is usually processed into the taper or straight pipe thread at the inlet and outlet ends of the valve, which can be connected to the taper pipe threaded joint or pipe. Because this connection can have large leaky channels, these channels can be blocked with a sealant, sealing tape, or packing. If the material of the valve body can be welded, but the expansion coefficient is very different, or the range of the change in operating temperature is large, the threaded connection must be honey sealed.
Threaded valves are mainly valves with a nominal diameter of less than 50mm. If the diameter is too large, it is difficult to install and seal the connection portion.
In order to facilitate the installation and removal of threaded valves, pipe joints are available at appropriate locations in the piping system. Valves with a nominal diameter below 50mm can use pipe sleeves as pipe joints, and the threads of the pipe sleeves connect the two connected parts together.
Second, the flange connection valve. Flange-connected valves are easy to install and remove. But it is heavier than a threaded valve, and the corresponding price is also high. Therefore, it is suitable for pipeline connection of various diameters and pressures. However, when the temperature exceeds 350 degrees, as the bolts, gaskets and flanges become loose, the load of the bolts is also significantly reduced, and leakage may occur to the flange connection under great force.
Third, the welding connection valve. This connection is suitable for a variety of pressures and temperatures, and is more reliable than flanged connections when used under more severe conditions. However, it is more difficult to disassemble and reinstall the welded valve, so its use is limited to places that can usually run reliably for a long time, or where the conditions are high, and the temperature is high. Such as thermal power stations, nuclear energy projects, ethylene projects on the pipeline.
Welded valves with a nominal diameter of less than 50mm usually have welded sockets to support pipes at the flat end of the load. Since socket welding forms a gap between the socket and the pipeline, it is possible that the gap will be corroded by some media, and the vibration of the pipeline will fatigue the connection part, so the use of socket welding is limited to a certain extent.
In the case of larger nominal diameter, load conditions and higher temperature, the valve body often uses bevel butt welding. At the same time, the weld joint has the original grid requirements, and we must use a skilled welder to complete this work.