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(1) Threaded connection valve

This connection is usually to process the valve in and out of the end into a tapered tube or straight pipe thread that can be connected to a tapered threaded joint or line. Because of the possibility of large leak ingress in this connection, sealants, sealing tape, or fillers can be used to clog these passages. If the material of the valve body can be welded, but the coefficient of expansion varies greatly, or the range of changes in operating temperature is large, the threaded connection must be welded honey seal. Threaded lying valves are mainly valves that are commonly known as general passages below 50mm. If the diameter size is too large, the installation and sealing of the connection part is very difficult.

In order to facilitate the installation and removal of threaded-connected valves, fittings are available in the appropriate position of the piping system. Valves with a common diameter of less than 50mm can be used as a fitting, and the threads of the sleeve joints connect the two parts of the connection together.

(2) Flange connection valve

Flange-connected valves, which are easy to install and remove. But it is more bulky than threaded-connected valves, and the corresponding price is higher. It is therefore suitable for a variety of diameter and pressure pipe connections. However, when the temperature exceeds 350 degrees, a leak may occur to the heavily constrained flange connection due to the relaxation of the bolts, gaskets and flanges, as well as a significant reduction in the load on the bolts.

(3) Welding connection valve

This connection is suitable for a variety of pressures and temperatures and is more reliable than flange connections when used in more time-called conditions. However, welding of connected valves is difficult to remove and reinstall, so its use is limited to the usual long-term reliable operation, or use conditions, high temperature occasions. such as coal-fired power stations, nuclear power projects, ethylene projects on the pipeline.

Welding valves with a common diameter of less than 50mm usually have welding sockets to undertake pipes at the holet plane end. Because the plug welding between the socket and the pipe to form a gap, so it is possible to make the gap by some media corrosion, while the vibration of the pipe will make the connection area fatigue, so the use of plug welding is limited.

In the case of a large nominal diameter, use conditions, high temperature, the valve body often uses bevel-to-welding, at the same time, the welding seam has the original requirements, must choose a skilled welder to complete the work.