Keyword: «preheating»

The paper studies the evolution of the thermal process during electrofusion welding of polyethylene pipes at low ambient temperatures. It is proposed to preheat the pipe assembly with a coupling by means of a built-in heater mounted in the body of the connecting part. To obtain a temperature distribution close to uniform in the heat-affected zone, alignment is carried out. The duration of heating and leveling are determined by calculation. It is proposed to control the cooling process using a built-in heater. The power of the embedded heater with controlled cooling is determined by the solution of the inverse problem of controlling the thermal regime of the technological process.

The welding of a branch saddle to a polyethylene pipe in open air at low temperatures is investigated. In contrast to previously studied electrofusion welding methods, the branch saddle's complex configuration prevents the application of established methods for determining welding parameters based on two-dimensional thermal process modeling. Three-dimensional mathematical modeling of the thermal process is employed to propose methods for determining welding parameters at low temperatures during the preheating and temperature equalization stages. The results indicate that the temperature distribution at the end of the equalization stage is non-uniform. Nevertheless, the boundaries of the heat-affected zones at the end of heating under standard conditions are nearly identical at both permissible and low temperatures.