Electrofusion jointing

Joints of all sizes may be made with heat fusion techniques. Fused joints may be made with either electrofusion or conventional heat fusion. Electrofusion joints are made with fittings which have embedded heating wires. Conventional fusion joints are made with special machines which trim the pipe ends, apply heat, and then force them together to form a bond. Consult the manufacturer regarding the sizes for which electrofusion fittings are available. 

The other popular type of electrofusion joint is the service saddle joint. This is used to make tee connections between a small diameter service and a larger diameter main pipe. These were also originally heated tool type welds but electrofusion reduces operative involvement and provides a greater level of control in fusion conditions. The technology has also been extended to larger size saddle connections that produce pipe branches that can be made whilst the main pipe is still under pressure. 

New pipe concepts with multilayer structures, or so-called functional layers, have helped to expand the applications of HOPE. Pipes with special protective layers (on the outside and/or inside) can be laid without a sand bed under some circumstances. This significantly reduces the pipe laying costs. There have also been new developments in joining technology. For example, electric welding fittings up to 700 mm are now available. Electrofusion jointing of PE pipes for gas distribution is also applied. 

There are basically two ways to oeate fused joints. The first type uses heating tools to heat the materials to be joined. A second type uses electric current to make an electrofusion joint. This is done for socket joints and saddle-type joints. 

Electrofusion is another way to join plastic pipe with a fused joint. The main difference between electrofusion and regular fusion joining is the process of heating the materials. An electrofusion joint is made by heating internally rather than externally. This can be done with either a wire coil at the interface of the joint or by the use of a conductive polymer. Electrical current creates the heat needed to fuse a joint. 

ISO 12176-2 2000 Plastics pipes and fittings - Equipment for fusion jointing polyethylene systems - Part 2 Electrofusion... 

Techniques, used by the gas and water industries to join and repair pipelines, include butt fusion, electrofusion socket welding and socket jointing (309). The study of bond strength testing for solvent joints in piping systems has noted extreme sensitivity to minor variations in sample preparation (259). 

Section of an electrofusion socket joint. The embedded copper wires have been used to melt the polyethylene sur ces. 

Electrofusion technology for PE joint connections is essentially common to gas, water and industrial applications of MDPE and HOPE pipes and, 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. Where pipework of mixed history may occur this is a considerable advantage over butt welding. Similarly pipes of the same outer diameter but differing thickness, which cannot be securely butt welded, may be electrofused. Electrofusion couplers have also been made for PP and PB industrial and heating pipe systems. 

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