# 2001 Munich
Crosslinked polyethylene (PE-X) pipes, successfully used for decades in house installations and heating systems, have found a new and growing application in buried gas and water supply systems, in recent years. The reason for the renewed success of PE-X is due to its unsurpassed resistance to notches. The use of sand bedding, usually required for PE pipe, can be eliminated with PE-X, owing to the notch resistance and other proven material advantages. The pipe can also be readily installed using trenchless methods (e.g. auger boring, hammer moles) without additional protective means or fear of damage. However, the decisive reason for the success of the pipe material is that there is a reliable connection method available, which works under site conditions, is simple and safe to handle, and of course also economical - electrofusion. When heated PE-X seems to have an elastomeric behaviour and in contrast with polyethylene it does not melt. This is the reason for PE-X in the past being considered not suitable for fusion jointing. The DVGW, German society for Gas- and Water distribution, awarded a contract for a research project to prove the fusion capabilities of peroxide crosslinked polyethylene (PE-Xa) with PE electrofusion couplers. In 1997 the positive results were published by GASTEC. Test-methods to prove the fusion characteristics of PE-Xa-pipes with electrofusion fittings made of PE80 and PE100 in general, and the fitness of purpose of the joints under site conditions shall be shown. In this presentation also an overview shall be given about latest research activities and results in fusion and butt welding of different PE-X types.