The medium-pressure gas pipeline from the year 1970 running underneath the Wehntalerstrasse had already exceeded its lifetime. In order to prevent potential negative consequences resulting thereof, Energie 360° AG decided to rehabilitate the steel transport pipeline preventively. In doing so, they wanted to keep the civil engineering effort as low as possible and the construction time as short as necessary. Traffic should continue to flow unhindered and residents should not be affected by noise, detours or even road closures. “This road has many residents and a lot of traffic. We can best organise this with a trenchless method,” explains Rosa Immler, Project Manager Network Infrastructure with Energie 360° AG.
Trenchless method preferred: Medium-pressure gas pipeline rehabilitated on a busy road in Zurich
The choice of the Zurich enterprise to realise the trenchless rehabilitation was taken in favour of the Primus Line® system by Rädlinger primus line GmbH from Cham in Bavaria. “We could rehabilitate a longer stretch with Primus Line®, because we needed less construction pits,” Rosa Immler is pleased. Instead of the originally planned 260 metres of rehabilitation, the final length was 420 metres. For this, only one start and one end pit were needed to insert the inliner along the entire length in one rehabilitation section within just a few hours. An intermediate pit served for cleaning the host pipe. Furthermore, the flexible inliner passed two 30°-degree bends on its way. Due to the static self-supporting capacity of the Primus Line® system, a targeted cross-section reduction was also achieved by installing a Primus Liner DN 250 in the old DN 300 steel pipe.
After completion of the preparatory works – shutdown of the steel gas pipeline by a separately commissioned civil engineering and pipeline construction company, cleaning and CCTV inspection twice each and milling off sharp-edged welding seams inside the pipe – the installation team of Rädlinger primus line GmbH pulled in the liner by means of a pulling winch. The liner was then rounded to its final form with the aid of pressurised air. Following the installation of the Primus Line system connectors, which were specially manufactured for this application, at the pipe ends and a successful pressure test, Energie 360° AG released the pipeline for operation again. After a total of only eight days of construction time – with just one day required for the insertion of the Primus Liner and the connector installation – the rehabilitation work was completed and the lifetime of the gas pipeline extended by another 50 years.
Since this was the first rehabilitation project of Energie 360° AG with the Primus Line® system, the Swiss energy company as well as the Bavarian manufacturer and their Swiss installation partner, Huber Leitungsbau GmbH, had invited interested, potential customers and media representatives for a site visit: Around 50 people accompanied the insertion of the liner live on site.
