PE Welding Machine

At the forefront of PE jointing technology is fusion welding, which can be used to join pipes directly or through fittings. Jointing methods for polyethylene pipe also include push-fit systems, mechanical couplings and many others.


FUSION WELDING

There are three methods of fusion butt fusion, electrofusion and hot iron. Butt fusion is a technique which has been used for many years in joining polyethylene pipes above 50mm. Electrofusion has now largely superseded the hot iron technique – used for jointing pipes with socket-type fittings.



BUTT FUSION
In butt fusion the pipe ends to be joined are brought together in a dedicated butt fusion machine. The end faces are squared up by planning with a mechanical trimmer, then heated with thermostatically controlled non-stick heater plate. When molten, the faces are pushed together and allowed to cool.
The butt fusion process generates weld beads both inside and outside the pipe. These can be removed easily to produce a smooth bore or outer surface. Inspection of the beads also provides a useful quality check on the weld.
Codes of practice for mains-laying stipulate that this jointing method should be applied to pipes only, thus all fittings are delivered to site with half-meter ‘pups’ of pipe prefabricated to them. Detailed instructions on butt fusion technique is given under ‘A Guide to Good Welding’ below.

ELECTROFUSION
This method uses socket-type fittings with integral heating elements to construct a pipe system. Couplers are used to join mains pipes; saddle fittings are used to connect service pipes. Fittings such a flange adaptors are spigotted and can be used in conjunction with electrofusion couplers and reducers.
Within an electrofusion fitting there is a resistive heating wire connected to surface terminals. An electric current passed through the wire melts the polymer and fuses the fitting to the pipe wall.
The pipe to be welded is first prepared by scraping away the outer surface layer, then pipe and fitting are clamped together to restrain movement. An electrical current is applied across the terminals from a generator via a control box (generally 40V in the UK). After welding the assembly is allowed to cool thoroughly before under clamping.