Generally speaking, the hot-melt connection of pe pipes is suitable for pe pipes with pipe diameter >: =dn63. The method is to weld pipes with a hot-melt machine, which is fast and low in cost, and suitable for pe water supply pipes and pe gas pipes. Related hot melt welding methods and precautions are as follows:
The hot-melt connection of pe pipes, that is, the hot-melt connection of polyethylene piping system, includes hot-melt butt joint (including saddle connection) and hot-melt socket connection. Hot-melt socket connection is suitable for pipes and fittings with relatively small diameters (generally below DN63), because the pipes and fittings with small diameters have thin walls and small cross sections, and it is difficult to guarantee the quality by butt joint. Hot-melt butt joint is suitable for pipes and fittings with larger diameter, which saves materials and is easy to manufacture than socket joint. Moreover, because the oxide surface layer is cut off before welding, the welding pressure can be controlled and the quality can be easily guaranteed. From the development trend, hot-melt docking is the mainstream.
The test shows that pipes and fittings made of different brands of polyethylene pipe special materials (which meet the standards and have little difference in melt flow rate MFR) can be connected by hot melt. However, because the commonly used materials of polyethylene pipes and fittings produced in China are not up to standard, it is suggested that different brands and batches of polyethylene pipes and fittings should be tested and tested before hot-melt connection.
Hot melting equipment-hot melting machine. The technology and equipment (tools) for hot melt connection of polyethylene pipeline system are relatively simple. In recent years, there are many problems in the joints of polyethylene pipeline laying projects in various places. The difficulty is that it is difficult to detect the quality of hot-melt connection on site (without destroying the connection). In foreign countries, ultrasonic testing of the quality of hot-melt joints is being explored, but it has not been widely used in the field. At present, this field is generally based on' visual testing'.
The guarantee of the quality stability of hot-melt connection mainly depends on strictly observing the specified operating procedures (especially strictly controlling the three parameters of temperature, pressure and time). It is suggested that polyethylene pipe fittings manufacturers should work out detailed operation procedures suitable for their own pipes and fittings through tests and tests according to relevant specifications (provisions of comparison principle) (combined with the characteristics of hot-melt connection equipment adopted). And help builders master the operating procedures through training and consultation.
Most large companies that produce polyethylene piping systems in the world have these operating procedures to guide hot melt connections. A practical quality control method is introduced in the PPI manual of the United States: a trial hot welding joint is made on site every day, and a' bending test' is carried out (no destructive test of equipment is needed) to judge whether it is necessary to adjust the process and equipment.