The connection joints of all polyethylene pipes must use electric fusion or hot fusion connection methods, and must not use mechanical connection methods. The joints of hot fusion connection are stronger than the pipeline itself. The joints or connectors are made of plastic, so there is no corrosion problem. The selection of the pipe connection method depends on the requirements and recommendations of the pipe manufacturer, as well as the technology mastered by the on-site construction personnel. The hot-melt connection first trims, cleans, and aligns the pipes, and then heats them to their melting point and connects them together.
In industry, we generally use hot-melt butt joints. The hot-melt butt joint is a method in which the end interfaces of polyethylene pipes are heated and melted by a heating plate and then joined together by cooling and fixing. Usually, a hot-melt electric welding machine is used to heat the end pipe, make it melt, and quickly attach it, maintain a certain pressure, and achieve the purpose of welding after cooling. Polyethylene pipes of all sizes can be connected by hot-melt butt joints. However, capacitor connection is recommended for pipes with a nominal diameter less than 63mm. This method is economical and reliable, and its interface has higher strength than the pipe itself in both tension and pressure.
Hot-melt connection preparation: the pipes of butt joints should be the same, and the same factory supporting materials should be used as far as possible; the outer diameter and wall thickness of the butt joints should be the same; the inner and outer surfaces of the welded pipes and fittings, especially the vicinity of the ports, should be smooth and flat. Abnormal shape; the size deviation of the pipe should meet the requirements; the butt pipe section should have good processing and welding performance matching the welding machine; check the welding system and power supply matching situation, clean the heating plate, and connect the power supply of each part of the welding machine , And should have grounding protection; set the heating plate temperature to the welding temperature according to the welding process parameters given by the welding machine; if it is an automatic welding machine, also set parameters such as heat absorption time and cooling time.
Key points of hot-melt butt welding operation: When using this method, the equipment only needs a hot-melt butt welding machine. The key points of operation are as follows: Place the connecting pipe on the welding jig and clamp it, then clean the pipe to be connected at the end, and mill the connecting surface. Straighten the two butt joints so that the amount of misalignment is not more than 10% of the wall thickness. Then put it on the heating plate and heat it up. After heating, take out the heating plate. Finally, the two heating surfaces are quickly joined, the pressure is increased to the welding pressure, and the pressure is maintained and cooled.
