Pipe joining | process feature
Preparation is very important when joining plastic pipes – whether the pipeline is buried underneath the city or out in the desert. Lou Reade reports
Putting it together
Whe n it comes to joining plastic pipe together, contrac- tors are faced with many different welding choices – each of which are valid in particular circumstances. Bartlomiej Grabski, research and development
specialist at Fox Fittings of Poland, told delegates at the recent Plastic Pipes in Infrastructure conference that electrofusion (EF) welding had become a universal method of connecting different types of polymer. He said that despite a few downsides to the tech- nique – such as the higher cost of fi ttings, reduced availability of fi ttings in larger sizes, and the need for more demanding preparation processes – it had become an established process due to a greater number of advantages. These included: a less complicated technology;
shorter welding time; faster installation; low cost and weight of the welding machine; the ability to repair active pipelines, and access hard-to-reach places; and, the ability to apply the fi ttings to just about any indus- trial and non-industrial installation. In terms of speed, he pointed out that fi ve hours of
welding – using EF – could cover around 15km, while a similar time on butt welding might cover around 5km. And, he stressed the wide range of materials that EF
can be applied to: from HDPE fi ttings, including for high pressure applications; PE-RT, to withstand tempera-
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tures above 110°C; many variants of polyamide; and specialist polymers such as PVDF, ECTFE and PB.
EF solutions Robert Eckert, manager of project management at Friatec in Germany, told delegates of a number of typical problems of EF joining issues – and how to solve them. “Preparation is essential for fusion quality,” he said,
listing a number of key processing criteria that must be followed. Remove oxide layer within required upper and lower limits using mechanical scraper tools;
Check that the jointing area is clean, dry and free of contamination; and,
Ensure correct pipe insertion depth of EF socket fi ttings and clamping of EF saddles. He also had advice regarding design criteria for EF fi ttings. Non-covered heating coils allow for direct heat transfer, while short fusion and cooling times are less sensitive to contamination of the pipe surface or oxide layer in fi tting jointing areas;
Long fusion zones improve reliability of strong joints, processed under site conditions;
Long pipe insertion depth and cold zones in the fi tting improve processing stability – even under pipe
June 2016 | PIPE & PROFILE EXTRUSION 37
Preparation is essential for pipe fusion quality, says Friatec
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