Most gas, water and industrial pipe distribution systems are specified to consist of high strength, rugged plastic
polyethylene and HDPE pipe. Sealing joined portions of PE and HDPE pipes has traditionally been accomplished by fusion
involving the application of heat to the areas to be connected. This renders areas in close proximity to the heating
element into a molten state, which is followed by the application of mechanical compression for completing the joint.
An alternative method includes a socket or outer sleeve with electric heating elements or wire conductors permanently embedded
in close proximity to its’ I.D. A piece of PE or HDPE pipe is inserted into each end of the sleeve until they butt up against
a stop positioned at the middle of the sleeve which prevents the pipe ends from meeting. An electric current is applied
to the conductor coil which heats both socket and pipe to a molten state thus fusing them together. After cooling,
the fused portions of the pipe and sleeve are rendered stronger then the pipe itself.
With the advent of newer sleeves and electrofusion equipment the process has become extremely simple with minimal
installer training required. But that does not mean that installation procedures need not be followed to the letter.
For successful joining of pipes, at least three important pipe preparation stages must be followed.
- Pipe ends must have finished squared ends to ensure that the central cold zones function to contain the melt.
- Pipe surfaces to be jointed must be properly scraped to reveal uncontaminated material. Any contamination on the pipe surface is retained at the joint interface, which can significantly reduce the strength of the joint.
- Pipe and fitting should be clamped during welding to eliminate relative movement to ensure molten polymer is contained at the fusion interface, allowing the development of a strong joint.
The advantages of electrofusion are many. The pipe segments can be preassembled in the socket and, because there is no hot tool to remove,
there is no pipe movement required during the installation process. This advantage alone facilitates pipe installation and/or
repair work in narrow trenches or restricted space confronted in entry/exit pits and urban manholes.
Because the coupler does not require direct pipe to pipe welding, the method can be used to join PE pipes with dissimilar
melt flow characteristics. Similarly, pipes of the same outer diameter but differing thickness may be electrofused.
Following is a list of ASTM Specifications that relate to Electrofusion of PE pipe:
- ASTM F2600-09 Standard Specification for Electrofusion Type Polyamide-11 Fittings for Outside Diameter Controlled Polyamide-11 Pipe and Tubing
- ASTM F1055-98(2006)Standard Specification for Electrofusion Type Polyethylene Fittings for Outside Diameter Controlled Polyethylene Pipe and Tubing
- ASTM F1290-98a(2004) Standard Practice for Electrofusion Joining Polyolefin Pipe and Fittings
- ASTM F2767-09 Standard Specification for Electrofusion Type Polyamide-12 Fittings for Outside Diameter Controlled Polyamide-12 Pipe and Tubing for Gas Distribution
