Welding metal tube forming part of plastic-metal-plastic composite pipe

摘要

The butted joint (4) of the metal tube (2) containing the inner plastic lining (1) is welded first. Second welds are then carried out on either side of the first. An Independent claim is included for the composite pipe produced. Preferred features: The second welding operation is divided into two independent welding processes. The complete sequence of welding operations pass a point (A) in succession. The first penetrative seam-welding operation consumes more power than the second welding operations. Transverse welding head (3a-3c) spacing can be increased from zero. The corresponding longitudinal spacing can be adjusted to 5 mm or more. The welding units have burners operated with a shielding gas. On completion of welding, the metal pipe is encased in a plastic outer pipe.