TRENCHLESS PIPE INSTALLATION | PROCESSING
Trenchless installation methods help to ensure that failing pipelines can be rehabilitated but with minimal disruption. Lou Reade reports
Infrastructure improvements
Pipe infrastructure – whether for fresh water, sewage, or gas – is failing in many areas of the world, as the existing network was often fitted many years ago. The job of ripping out old pipe and fitting new is time-consuming and expensive, which is why many authorities are choosing to use various forms of trenchless technology – where a flexible plastic pipe is inserted inside the existing concrete or steel pipe. For instance, Agru of Austria has used trenchless
installation to fit a PE100-RC pipe inside a leaking sewage pressure line near Linz, in order to keep traffic disruption there to a minimum. The project uses the Agru Close-Fit liner for the
renovation. This pressure-resistant liner is designed for relining without an annular gap and can be pulled in through existing shafts or small trenches thanks to its small bending radii. In the area concerned, just a few metres sepa-
rate the B129 main road and the River Danube, which run parallel to each other. The sewer to be repaired lies directly behind the crash barrier. Replacing the 5.2km section using the ‘cut-and- cover’ method would have reduced the width of the road and caused severe traffic disruption. To
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overcome this, trenchless rehabilitation of the ductile cast pipe system was chosen. The renovat- ed pipe must be able to withstand an operating pressure of 3 bar.
Due to the long lengths involved (up to 620m), the PE liners had to be shaped on-site. The Close-Fit liners are usually folded at the factory, meaning this project placed new demands on the lining system. Civil engineering company RTI Austria, which specialises in pipe renovation, was awarded the contract. RTI uses Agru’s Close-Fit liner for its pressure pipe renovations, which for this project is made of PE 100-RC. The liner is a folded pipe that is easy to pull into an old pipe in need of repair because of its reduced cross section. Its ‘memory effect’ enables it to reshape itself into a circular pipe after installation, using pressure and temperature. This causes the Close-Fit liner to lie tight against the old pipe and form a frictional connection with it. This method allows the greatest possible internal cross section to be retained in the old pipe and an annular gap to be avoided completely. The surface of the Agru Close-Fit liner remains smooth throughout its service life, improv- ing the flow properties of the sewerage line.
� September 2018 | PIPE & PROFILE EXTRUSION 39
Main image: Agru’s close-fit liner is a folded pipe that is easy to pull into an old pipe because of its reduced cross section
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