Cooling Times for PE100 Electrofusion Joints

After electrofusion welding a PE100 joint, the prepared joint must not be disturbed or stressed, prior to completion of the manufacturer’s recommended fusion cooling time. PE100 Electrofusion joints should cool to ambient conditions, before filling the pipeline and must not be quenched to rapidly cool the fusion joint. Polyethylene crystallizes as the polymer melt cools, where the length of this cooling period affects the mechanical properties of the PE, as the polymer melt solidifies to form the joint. Polyethylene consists of long molecular chains (macromolecules).  These molecules may be branched and the degree of such branching and the length of side chains have an important effect on the properties of polyethylene.  Parts of the long molecular chains arrange themselves by folding into very small crystallites which are joined together by amorphous regions to form macrostructures knows as spherulites.  The shorter the chains, and lesser the branching, the better the process of crystallization. The crystalline region has a higher density than the amorphous region and therefore different density values are obtained depending on the degree of crystallinity. The longer the fusion cooling time the better the creep tensile strength development and long term performance of the joint.  As a result the degree of crystallinity, molecular orientation and the ramella structure vary with the cooling time, where differences of molecular structure change the long term performance of the joint. Electrofusion welding machines are uploaded with heat fusion and cooling programs to ensure the joint develops optimum properties. Deviations from the standardised conditions voids any warranty and creates an uncertainty for the joint performance and long term...

Reply to Machines and Tools for PE Jointing

It is always strongly recommended for any installer to comply exactly with the manufacturers recommended and published installation procedures. This includes the use of the manufacturer’s recommended cleaning fluids and methods. The use of incorrect cleaners can result in joint failure. Georg Fischer recommends a minimum concentration of 85% isopropyl or ethanol alcohol be used to ensure complete evaporation and removal of dirt & grease from the fusion area.   The PIPA document POP001 – installation guidelines for EF and published by the  Plastics Industry Pipe Association of Australia  also details the recommended jointing methods that must be adhered to. This document is available via the website www.pipa.com.au .   Some of the most common reasons for jointing failure during electrofusion welding are: Contamination of the fusion area, e.g. bad handling and cross-contamination. Ineffective peeling and removal of the oxide layer on the PE pipe. Misalignment in the joint and fittings due to the lack of the use of alignment clamps Inadequate insertion of the pipe into the EF fittings   Electrofusion jointing is the welding together of the un-oxidised and uncontaminated PE fitting and pipe surfaces to form one homogenous layer in the fusion area. Peeling and cleaning of the fusion area are critical aspects of the electrofusion process and particular care needs to be taken when jointing.   The need to use alcohol cleaning tissues has been recommended standard practice and part of GF’s Installation Procedures for many years. The purpose of alcohol based cleaning fluids is to act as a de-greaser and cleaner of the FUSION SURFACEs ONLY. It is recommended that the manufacturers recommended cleaning wipes...