Electro-fusion and Butt Fusion of Pipes FAQs
Q: What is electro-fusion?
A: Electro-fusion is used to weld pipes made from polyethylene (PE) in the water industry.
The system allows the jointing of pipes and fittings with minimal equipment. It is easy to use for repairs and needs little space.
The electro-fusion process uses fittings which the ends of pipes are introduced to. An internal stop (central register) prevents the pipe ends from meeting and ensures that both pipes are entered sufficiently far in to the fitting.
Fusion indicators are often featured in the fitting, so that once sufficient melt pressure has been achieved the indicators will protrude - showing that the welding process has been completed successfully.
A careful joint preparation procedure is followed to ensure that contamination and displacement effects which could compromise the fusion process are minimised.
Pipe joint ends are finished square to ensure that a central cold zone contains the melt. Pipe surfaces are scraped to expose (un-oxidised) uncontaminated polythene and pipe and fitting are clamped during welding to eliminate relative movement and ensure that molten polymer is held at the fusion interface to develop a strong joint.
Electrofusion fittings are typically available in sizes from 16mm to 500mm. However, sizes up to 710mm are now available.
Q: What is butt fusion?
A: Butt fusion welding is used in the water industry for welding pipes made from polyethylene (PE). Pipe work is held within clamps to ensure perfect alignment before use of the butt fusion equipment. Pipe ends are planed to ensure that they are flat and square and re-checked for alignment.
A flat hot plate is positioned between the two pipe ends. The pipes are pushed towards each other and come into contact with the hot plate. The pipe ends melt and the contact pressure forces the molten polythene to form 'weld beads' inside and outside the pipe.
Pressure is then reduced whilst just maintaining pipe contact with the hot plate. This allows the melt depth to increase and at the end of this 'heat soak' stage, the pipe ends are pulled away from the hot plate. The hot plate is removed, and the two molten pipe ends are pushed together. This causes further growth of the weld bead and is called the 'bead roll over' stage. The pressure is maintained until the weld is fully cooled.
Butt fusion welding of thermoplastic pipes can be carried out on a wide range of pipe sizes, typically between 63 and 800mm outside diameter. Manual, automatic and semi-automatic butt fusion welding machines are available commercially from a number of suppliers.
