The connection joints of all polyethylene pipes must be connected by electric fusion or thermal fusion, but not by mechanical connection methods. The joints of thermal fusion connection are stronger than the pipeline itself. The joints or connectors are made of plastic and there is no corrosion problem. The choice of pipe connection method depends on the requirements and recommendations of the pipe manufacturer, and the skills of the site construction staff. Hot-melt connections are first trimmed, cleaned, aligned, and then heated to their melting points and joined together. There are two types of hot-melt technology in the industry: hot-melt and socket connection.
⑴Hot melt butt
Hot-melt butt jointing is a method in which the end interfaces of polyethylene pipes are heated and fused with a heating plate to fuse with each other, and are fixedly connected together after cooling. Usually, a hot-melt electric welding machine is used to heat the end pipe, make it melt, quickly attach it, maintain a certain pressure, and cool it to achieve the purpose of welding. Polyethylene pipes of all sizes can be connected by hot-melt butt jointing. However, for pipes with a nominal diameter of less than 63mm, capacitor connections are recommended. This method is economical and reliable, and its interface has higher strength than the pipe itself when under tension and pressure.
Ready to work. The butt pipe sections should be consistent in pipe material, and the same factory supporting materials should be used as much as possible; the outer diameter and wall thickness of the butt pipe section should be the same; the inner and outer surfaces of the welded pipe and fittings, especially near the port, should be smooth and flat, without abnormalities; the size of the pipe Deviations 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 conditions, clean the heating plate, switch on the power of each part of the welding machine, and there should be grounding protection ; Set the temperature of the heating plate to the welding temperature according to the welding process parameters given by the welding machine; if it is an automatic welding machine, set parameters such as heat absorption time and cooling time.
Main points of hot-melt butt operation. When using this method, the equipment only needs a hot-melt butt welding machine. The operating points are as follows: Place the pipe with the connection on a welding fixture and clamp it, then clean the end to be connected to the pipe, mill the connection surface, and straighten the two butt pieces. The amount of dislocation is not more than 10% of the wall thickness. Then put it on a hot plate to heat. After heating, remove 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.
⑵Hotmelt socket connection
Hot-melt socket connection In the hot-melt socket connection, the two end portions of the pipe to be connected are respectively heated and melted with the ends of a thicker pipe section, so that each joint requires two hot-melt processes.
When hot-melt socket connection, the pipe port should be chamfered and the connection surface should be cleaned. Draw a marking line on the socket end, and use a heating tool to heat the pipe and fitting connection surface at the same time. When DN≥63mm, use the heating tool of the mechanical device, otherwise it is a manual heating tool. Immediately after heating, exit the heating tool and use a uniform external force to extend the socket into the depth of the socket to reach the standard line to form a uniform flange at the end of the socket.
