Method and device for the welding of pipes

摘要

Pipes of a weldable polymer material are welded with a muff of a weldable polymer material. The method includes 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, and 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. The temperature of the weld is calculated through adding the initial ambient temperature of the weld and the increase in temperature of the band.

主权项

1. 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, wherein the initial resistance of the band is calculated as a ratio of voltage across the band and current supplied to the band before the band is heated; 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, wherein the current is supplied such that the temperature of the band is caused to reach a first target value of temperature during a heating phase, wherein the temperature of the band is caused to reach a second target value of temperature during an equilibrium phase, and wherein the first target value of temperature is higher than the second target value of temperature; 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 as a difference between the resistance of the band and the initial resistance of the band; calculating the increase in temperature of the band based on the change in resistance based on the change in resistance and a material-specific conversion factor; 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, wherein the calculated temperature of the weld is compared with a pre-determined final temperature of the weld, and wherein the supply of current to the band is terminated when the temperature of the weld has reached the pre-determined final temperature of the weld.