What is Poly Welding
There are three types of Poly Welding: Butt Fusion Welding, Electrofusion Welding, and Extrusion Welding.
Butt Fusion Welding:
Butt Fusion is a common method for joining HDPE Pipe, especially larger lengths. To do this, a Butt Welding machine is used to hold, face, and heat the two pipe ends, before pressing them together hydraulically and holding them in place until the join cools, welding the two ends together.
Electrofusion is a method of joining HDPE and other plastic pipes using special fittings that have built-in electric heating elements which are used to weld the joint together.
The pipes to be joined are peeled and cleaned, inserted into the electrofusion fitting and a voltage (typically 40V) is applied for a fixed time depending on the fitting in use. The in-built heater coils then melt the inside of the fitting and the outside of the pipe wall, which weld together producing a very strong homogeneous joint. The assembly is then left to cool for a specified time.
Electrofusion welding is beneficial because it does not require the operator to use dangerous or sophisticated equipment. After some preparation, the Electrofusion Welder will guide the operator through the steps to take. Welding heat and time is dependant on the type and size of the fitting. All Electrofusion Fittings are not created equal – precise positioning of the energising coils of wire in each fitting ensures uniform melting for a strong joint and the minimisation of welding and cooling time.
The operator must be qualified according to the local and national laws. In Australia, an Electrofusion Course can be done within 8 hours. Electrofusion welding training focuses on the importance of accurately fusing EF fittings. Looking at both manual and automatic fittings you will learn the importance of preparation, timing, temperature, pressure and cooldown.
To keep their qualification current, a trained operator can get their fitting tested, which involves cutting open the fitting and examining the integrity of the weld.
Another type of Poly Welding is Extrusion. Extrusion welding is done with a hand tool, known as an Extrusion Welder.
An Extrusion Welder has a nozzle for hot air and an extruder that pushes filler material out. The process involves heating the two joining surfaces and adding a material filler (extrudate). The extrudate is applied using pressure and then allowed to cool, welding the surfaces together.
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