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How to connect valves and pipes?


How to connect valves and pipes?

Valves are usually connected to pipelines in various ways such as thread, flange, welding, clamp, and wafer. So in the selection of use, how to choose?

Threaded connection. Threaded connection is the form in which the two ends of the valve are processed into internal threads or external threads to connect with the pipeline. Generally, ball valves below 4 inches and globe valves, gate valves and check valves below 2 inches are mostly threaded.

The threaded connection structure is relatively simple, the weight is light, and the installation and disassembly are more convenient for maintenance and replacement. Since the valve will expand under the influence of ambient temperature and medium temperature during use, in order to ensure good sealing performance, the expansion coefficients of the two materials at the connection end should be fully considered.

There may be large leakage channels in threaded connections, so sealants, sealing tapes or fillers can be used to block these channels to increase the sealing performance. If the process and the material of the valve body can be welded, it can also be sealed after the threaded connection. Sex would be better.

Flange connection. Flange connection is the most common connection method in valves. Installation and disassembly are very convenient, and the flange connection is reliable in sealing, which is more common in high-pressure and large-diameter valves. However, the flange end is heavy and the cost is relatively high.

Moreover, when the temperature exceeds 350 ℃, due to the creep relaxation of bolts, gaskets and flanges, the load of the bolts will be significantly reduced, and the flange connection with great stress may leak, which is not suitable for use.

Welded connection. Welded connection usually has two structural forms: socket welding and butt welding. Generally speaking, socket welding is used for low-pressure valves. The welding structure of socket welding valve is simple to process, and the welding installation is also convenient;

The high-pressure valve has a high cost, and the welding needs to be grooved according to the pipeline standard, which is difficult to process, and the welding and installation process is also more complicated. In some processes, radiographic non-destructive testing is also required for the connection welding.

When the temperature exceeds 350 °C, the load of the bolts will be significantly reduced due to the creep relaxation of the bolts, gaskets and flanges, and leakage may occur in the flange connection with great stress.

Clamp connection. Clamp connection structure is similar to flange, but its structure is light and low cost is commonly used in sanitary pipelines and devices. Sanitary pipelines need to be cleaned, and it is strictly forbidden to have residues to produce bacteria, so flange connections and threaded connections are not suitable, and welding connections are difficult to install and disassemble. Therefore, clamp connections are the most common in raw pipelines. a connection method.

Wafer connection. Wafer is generally more common in butterfly valves and check valves. In valve installation, the valve needs to be clamped between two flanges. Compared with flange connection, wafer connection is more cost-effective. , easy to install.

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