MACHINERY | PIPE INSPECTION


Right: Sikora’s Centerwave 6000, which will be seen at Fakuma next month, uses millimetre wave technol- ogy to measures pipe dimensions


by measuring weight loss. Pipe samples were exposed to 100% hydrogen for 1,000 hours – and found no evidence of chemical attack. And, while hydrogen is a far smaller molecule than methane – and so might be expected to permeate a plastic barrier more easily – Kiwa found that perme- ability was low. Projected gas low was very low – at less than 1m3


per year from


an SDR 11 pipe at 2 bar. Because it is such a small


amount, he said that venting the hydrogen was a safe option, with minimal risk of fire or explosion. To further mitigate the risk, he said that a casing pipe should not be used – in case of hydrogen build up.


Kiwa also found that PE100 was suitable for welding after exposure to hydrogen (allowing the use of electrofusion coupling to repair pipes). “It is possible and safe to use PE100 RC to


transport hydrogen,” he said, but stressed: “In service, safety precautions – such as a more frequent leak surveys – must be taken, due to the different nature of hydrogen.” Another area of concern was fracture toughness when moving from methane to hydrogen – which Hermkens said “needed evaluation”.


Facing failure At the same event, Michail Kalloudis, technical manager at Impact Solutions, took delegates through the many reasons for pipe failure – and how testing can help to avert them. He said a using a combination of “popular, accurate, efficient and low cost” techniques could help to determine potential problems in the raw material. These techniques include: Fourier Transform


Infrared spectroscopy, which gives a ‘fingerprint’ of a polymer sample; differential scanning calorimetry (DSC), which accurately measures thermal transi- tions such as melting and crystallisation in a polymer – which can determine contamination; thermogravimetric analysis (TGA), which gives information on thermal stability; and melt flow rate (MFR) analysis, which determines the molecular weight of the polymer. “These techniques still require experts to do the


analysis,” said Kalloudis. He added that they can be supported by more


18 PIPE & PROFILE EXTRUSION | October 2018


advanced techniques such as scanning electron microscopy (SEM), gas chromatography- mass spectrometry (GCMS) and nuclear magnetic resonance (NMR). Kalloudis presented


several case studies to illustrate various types of pipe failure, including hot water PVC pipe and PE100 water pipes. Several failures of the


PVC pipe had caused a factory shutdown. Some pipe sections were re- moved and analysed by DSC – which revealed that the PVC’s glass transition temperature had been


lowered – as the elevated temperatures had led to thermal relaxation and resulted in physical ageing. PE100 water pipe butt welds were exhibiting


brittle mode failures, though no problems were identified in the welding process. The problem was identified through micrographs – which revealed large agglomerates of carbon black. This was confirmed using SEM. In a similar case, a butt fusion-welded PE100 pipe showed excessive blistering on the welding surface – though DSC, FTIR and SEM showed nothing suspicious. However, GCMS revealed trace amounts of a saturated hydrocarbon on the non-heated side of the pipe – leading to the conclusion that diesel had contaminated the PE100 during processing.


As well as using techniques like these to identify


the reasons for failure, Kalloudis said it was vital to implement effective QA and QC programmes. “Although a lot of research has been done in the


production of PE pipe materials, bad QA and QC processes can threaten the pipelines,” he said. “Contractors and utility companies must establish tight QA/QC procedures and follow the require- ments of the relevant standards.”


CLICK ON THE LINKS FOR MORE INFORMATION: � www.festo.com � www.echologics.com � www.zumbach.com � www.betalasermike.com � www.inoex.de � www.sikora.net � www.kiwa.com � www.impact-solutions.co.uk


www.pipeandprofile.com


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