Method and device for the welding of pipes

A method of welding a pipe of a weldable polymer material to a muff of a weldable polymer material, where the pipe has ends, where the method comprises:

• placing the muff with an overlap over the ends of the pipes;
• welding the muff to the ends of the pipes through placement of an electrically conducting band that is permeable to molten plastic between the pipe and the muff;
• connecting a power supply to the band through feed cables;
• measuring the initial ambient temperature of the weld;
• calculating the initial resistance of the band;
• supplying an electrical current in order to heat the band and the surrounding polymer material such that they melt together around the band in order to form a weld,
• measuring a voltage across the band;
• measuring the electrical current-supplied to the band;
• causing the electrical current supplied to the band to increase;
• calculating the resistance of the band based on the voltage and the measured current;
• calculating the change in resistance;
• calculating the increase in temperature of the band based on the change in resistance;
• calculating the temperature of the weld through adding the initial ambient temperature of the weld and the increase in temperature of the band;
• and
• terminating supply of current to the band based on the calculated temperature of the weld.