What is the difference between electrofusion and hot melting for urban gas pipelines? Also, why is it necessary to cut and flange the pipe during hot melting?

Electrofusion and heat fusion are two different welding techniques, primarily used for joining plastic pipes such as PE (polyethylene) pipes, which are widely used in urban gas piping systems. **Electrofusion joining **is a method of connecting pipes by melting an electrofusion joint (which contains heating wires). The voltage generates heat at the joint, and this heat melts the joint and the pipe, forming a single unit. This method requires a dedicated electrofusion welding machine, which can precisely control voltage and time to ensure stable welding quality. The advantages of electrofusion joining are simple operation and stable joint quality, but the equipment cost is high. **Hot melt welding** (commonly referred to as hot plate welding or butting welding) involves using a hot plate to heat the ends of a pipe until they melt, after which the two ends are pressed together to form a single unit. This method does not require additional connectors, the equipment is simple, and the cost is low. However, this method requires a higher level of technical skill, and the quality of the connection is greatly influenced by the operator’s proficiency. As for cutting the flange, this is an important step in the heat fusion joining process. After heating, a layer of molten material forms on the molten surface of the pipe; this is what is known as \"flanging\". If this layer of molten material is not removed, it will harden as it cools, which may affect the sealing quality and strength of the joint. Therefore, it is necessary to remove this layer of molten material immediately before pressing to ensure the quality of the connection. .