Socket fusion welding is a widely used technique for assembling plastics piping systems using injection moulded fittings. Operating principles are straightforward, the welding cycle essentially consisting of a heating phase and a cooling/welding phase.
A metal socket mounted on a hot plate heats the outside circumference of the pipe (see process schematic below). Heating occurs along a defined length which will vary depending on the size of pipe and fitting being welded. A metal spigot on the opposite side of the hot plate simultaneously heats the inside surface of the injection moulded fitting. The length of the heated region is the same as that for the pipe.
Both fitting and pipe are heated for a set length of time after which the heated socket/spigot tooling is removed and the pipe is pushed into the fitting. Pipe and fitting are left for a predetermined time to cool and form a weld.
Depending on the size of pipe, socket fusion welding can either be done by hand or carried out on a manually operated machine.
More information is available in Butt and socket fusion welding of plastic pipe - a guide to best practice.
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