PVC-O pipe | materials feature
Whether it’s made from nylon, PEX, PVC-O or PE100, pipe that can withstand high pressures is appropriate for a wide range of applications. Lou Reade reports
Keeping the pressure on
Modern grades of polyethylene such as PE100 are increasingly specifi ed for high pressure pipe applica- tions like gas and water transport – and it is vital that their lifetime is accurately assessed. Frans Scholten, senior consultant for polymeric
materials at Kiwa Technology in the Netherlands, told delegates at the recent Plastic Pipes in Infrastructure conference that his company is developing a new test that may one day be able to predict accurately the lifetime of the latest generation of tough HDPE plastic pipes. The company is doing this in a curious way: by analysing samples of old PE50 plastic pipes. “These are the fi rst generation of HDPE plastic pipes, which were installed between 1961 and 1979,” he said. “Many are still in the ground, especially in Germany and the Netherlands.” His research is trying to understand the infl uence of
point loads on plastic pipe lifetime. A point load happens when something like a stone or tree root presses on the outer surface of the pipe. Excess plastic material is then forced through the pipe, so that a bulge appears on the inner surface – which generates tensile stress that can cause pipe failure. “This is the only generation of HDPE pipe for which
actual failure data is available,” he said. Point loads cause PE50 to fail prematurely, as it adds
to the stress caused by the internal gas or water pressure. The fi rst failures were seen in 1987. “This puts the pipe lifetime at between eight and 26
www.pipeandprofi
le.com
years – when it should be 50,” he said. Next, he says he will continue to test PE80, PE100 and RC materials. He said that PE80 pipes tend to last around 10 times longer than PE50 pipes in point load testing. “We want to know when PE80 pipes fail,” he said. “Will it be before or after 50 years?” Kiwa also intends to develop point load tests for PE100 RC pipes.
Oriented pipe Dutch water company WMD recently installed a 19km molecularly oriented PVC (PVC-O) pipeline – using Biax pipe from Wavin – between the cities of Assen and Beilen. All pipe sections were 24m long and were jointed together with double couplers and a total of 200 tensile resistant joints. Also, 60 tensile resistant bends were installed. Water from Assen was of the right level of hardness, so it was transported to Beilen via the 400mm PVC-O potable water transport pipeline. It helped WMD resolve two problems. Firstly, drinking water produced in Beilen could be mixed with softer water from Assen, ensuring supply of good water quality to all the customers. And secondly, the pipeline also supplies water in case of “calamities”. By connecting both cities, each city can supply the other city with drinking water in case of maintenance or extension of the network. WMD chose Biax pipe because it knew that PVC-O
June 2016 | PIPE & PROFILE EXTRUSION 23 PVC-O pipes
are far lighter than those made from traditional
materials like ductile iron
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54