Pre-installation: the most important link of the pre-installation of the sleeve type pipe joint, directly affects the reliability of the seal. Special precursors are generally required. Small diameter joints can be preinstalled on the bench pliers. The specific approach is to use a connector as a matrix, the nut, sleeve pressure on the pipe can be. There are mainly bayonet straight pipe connector, bayonet end straight through connector, bayonet three - way pipe connector and other types. The author found that, even if it is a batch of goods from the same manufacturer, the depth of the conical hole on these joints is often not the same, resulting in leakage, and this problem is often ignored. The correct way is to use what kind of joint body to connect one end of the pipe, and preinstall the corresponding end with the same type of joint, so as to minimize the leakage problem. (2) pipe end should be flush. After the pipe is cut, it shall be polished flat on the grinding wheel and other tools, and the burr shall be removed, cleaned and cleaned with high-pressure air before use. (3) pre-installation, should try to maintain the tube and joint body coaxiality, if the tube deflection is too large will cause sealing failure. (4) the pre-installed force should not be too ambassador sleeve of the inside edge just embedded in the pipe wall, the sleeve should not be obvious deformation. When connecting pipelines by the Carbon Steel Pipe running nipple, assemble according to the specified tightening force. ф 6-1 card set of tight force of 15 n, 16, 64-1 ф mmr259n 18 mm, ф 450 n. If the sleeve is badly deformed during pre-installation, the sealing function will be lost.