Electrofusion has been used successfully for joining PE pipes for approximately 50 years. Over time the range and size of fittings has increased markedly with diameters now available beyond DN1000. Standardisation of pipe and fittings compounds and performance requirements of the EF equipment has resulted in EF being a very reliable jointing method provided the correct procedures are followed.

International Standards Organisation (ISO) has expert working groups responsible for destructive and non-destructive testing of PE joints, resulting in the publication of several Standards and Technical Specifications.

For EF assemblies, the destructive peel decohesion test has long been a primary means of validating the combination of technique, equipment and materials in diameters equal to or greater than 90 mm. An ISO crushing decohesion test has also existed for many years. Thirteen years ago the strip bend test was also adopted as an ISO test method. These tests have two components. Firstly, there is the mechanical test followed by subjective interpretation.

Locally and internationally, it has been recognised that a lack of understanding of the EF process has sometimes led to misinterpretation of peel decohesion results and unfortunately the condemnation of good welds. ISO TC138 SC5 WG12 (Test methods for polyolefin pipe fitting assemblies) is currently revising both ISO 13954 (Plastics pipes and fittings — Peel decohesion test for polyethylene (PE) electrofusion assemblies of nominal outside diameter greater than or equal to 90 mm) and ISO 21751 (Plastics pipes and fittings — Decohesion test of electrofusion assemblies — Strip-bend test) to provide more guidance regarding the interpretation phase and to rationalise the terminology in the two methods. Additionally, the strip-bend procedure is being updated with respect to the equipment needed and specimen details to provide an acceptable level of repeatability.

Improvements to both methods will include detailed photographs showing acceptable and unacceptable fracture surfaces and, for example, that tearing of the PE fitting material between the heating wires must mean a satisfactory fusion has been achieved across the pipe – fitting interface. In the meantime, PIPA has published POP020 (Principles of polyethylene (PE) electrofusion welding and assessment) to assist in the interpretation of the results of the peel decohesion test.

With respect to non-destructive testing of EF welds, ISO TS 16943 -2023 (Thermoplastic pipes for the conveyance of fluids — Inspection polyethylene electrofusion socket joints using phased array ultrasonic testing) has been published. A micro-wave technique is expected to follow.