processing | Infrastructure pipe Right: GPS


is involved in the London Medium Pressure


project to fit 29km of gas pipe across the city


sulphide, shear and joint failure, and aggressive ground water. Kaye said that PVC-O’s lower modulus of elasticity


helped it to keep surge pressures low – around 75% lower in this case. “This is significant not just for the pipe itself, but for


other components in the piping system,” he said. At the same time, its thinner walls – compared with


HDPE – resulted in a 25% lower velocity, which helped to reduce surge pressures, even bearing in mind HDPE’s lower modulus. “PVC-O was the best of all the plastics for coping


with surge – and all plastics fared better than ductile iron,” he said.


PVC-O benefits Wavin said that MRS50 material classifications for bi-oriented PVC-O have now been developed for larger diameter pipe – meaning that 20 or 25 bar applications are now feasible for drinking water. “Alternatively, significant weight savings can be


achieved when MRS50 substitutes MRS45,” said Andre Nijland, of Wavin Overseas. He accepted that “significant” extra investment was needed in PVC-O, but that the savings – a 58% reduction in resin, for instance – meant that payback was “quite short”.


He added that the capability of PVC-O has reached a


ceiling. “We are reaching almost the limit of what’s possible


wit PVC,” he said. “There may be some gains with certain formulations, but it would only be incremental.” He also told delegates that Wavin has developed a


Future needs for water pipe


In his presentation, Steve Kaye of Anglian Water Services said he looked forward to the day when plastic pipes could be made ‘smarter’ – by imbuing them with sensor capability, for instance. “I’d also like to see disinfectant pipes – so there is no need for


chemicals,” he said. For now, the only answer to this problem is to develop pipe that is


resistant to disinfectant chemicals, such as by using an internal PVDF layer, or by choosing PEX. Repsol of Spain shared details of a pure HDPE pipe material that it says can withstand the effect of chlorine dioxide – a common disinfectant. Alvaro Perez, technical assistance engineer for PE/PP pipes, said that


the company’s Alcudia T100NLS-RD and T80N-RD grades include additives that help them to resist attack by disinfectant – by protecting against phenol extraction from the polymer. In a range of tests – including elongation at break, OIT and leaks – the grades outperformed a number of PE100 grades, he said.


18 PIPE & PROFILE EXTRUSION | June 2017


new coupler for use with PVC-O pipe that allows for pipe movement – such as when pipe is installed in soft soils, or an earthquake zone. The prototype has been built, and moulds are ready,


he said. “We expect to launch it in Latin America this year, then it may be expand it through other Wavin companies worldwide,” he said. The plan is to introduce it for smaller pipe, and work


towards larger diameters, he said. For its part, Molecor of Spain – which makes PVC-O pipe and the machinery to produce the pipe – said that it had recently developed machinery to make products up to 1200mm in diameter. The company currently produces pipe up to 800mm


diameter, but plans to move up to 1200mm pipe in the near future. Recently, it has also developed a new line of PVC-O fittings, which it said was a very complex project. However, it expects the products – elbow, coupler, repairing coupler and reducer, up to 400mm – to be available towards the end of this year. The advantage, said Molecor, is that PVC-O pipes will be connectable with fittings in the same material – rather than ductile iron.


Looking ahead, the company said there was still


room to expand into larger diameter pipes – possibly as far as 2000mm diameter.


Pressure’s on Dominic O’Sullivan, head of product marketing at GPS PE Piping Systems, explained details of a huge project to install new gas pipe in London. London Medium Pressure is an £18bn project that will lay 29km of gas main over the next eight years. It is expected to affect around 2m people.


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PHOTO: ALIAXIS


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