THERMOPLASTIC FITTING ELECTRIC HEAT WELDING METHOD AND APPARATUS

摘要

Thermoplastic fitting contg. an electric resistance heating element is heat welded by supplying a regulated quantity of electrical power to it thereby ensuring a high quality weld. The fitting is connected to a controlled electric power source and the initial magnitude of the current flowing through the resistance heating element is sensed and its magnitude compared with predetermined current levels for various sizes of fittings to determine the size of fitting being welded and the total time for which the controlled electric power should be supplied to make a high quality weld. The control equipment continues to sense one or more electrical characteristics of the resistance heating element during the time the power is supplied comparing the characteristics at predetermined time intervals with predetermined current levels.