There are two types: one is cutting, that is, pulling out a short pipe. Used for welding pressure points and pressure valves on pipelines. One is the short section of external thread. In other words, there is an external thread at one end, usually kg1 / 2 ', and there is no thread at one end. After determining the pressure point on the pipeline, weld the end without screw to the pressure point (open hole) of the pipeline, and directly tighten the internal thread stop valve (primary valve) at the end with screw. No matter what form of pressure is applied, the installation of pressure source components must meet the following conditions