Stadwerke Klagenfurt operates a pipeline network of approximately 525 km in length, which covers an annual water consumption requirement of almost 9 million cubic metres.

Stadtwerke Klagenfurt Head of the Underground Works Division Günther Kumerschek said “It is our job to make reliable plans for the future. That is our reason for attaching great importance to pipes and pipe materials which are safe, secure and durable. The experience we have had in the past with Duktus pipes has been excellent.

“That is why we have again relied on ductile iron pipes from Duktus for this latest operation, which comprised the replacement of 1 km of drinking water pipeline within the municipal area.”

There were four stretches of road where old pipelines had become damaged and needed to be replaced. Hydraulic calculations showed that a reduction in cross-section was not possible and that there were even areas that needed to be increased by at least one pipe size.

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A consultation between Stadtwerke, Duktus’s Applications Engineering Department and Swietelsky-Faber, who was contracted to complete the installation work, determined that the pipe bursting technique would be the most economical method of replacement and the best one in technical terms.

The Duktus pipe system was selected for the job because of its cement mortar coating (ZMU), which is able to meet all the demands made by the pipe bursting technique, and the large pulling forces the joint used with the pipe is able to withstand.

Stadtwerke Klagenfurt Head of Water Business Area Erich Plimon said “The decision to use the ductile material for the new pipes meant that we were on the safe side, because the fragments of the old grey cast iron pipelines would have been too much of a risk with any other material.”

Because the soil was a difficult coarse gravel, the four pipe burst installation sites, totalling 1 km in length, were divided into sections of approximately 150 m.

A 40 tonne bursting rig, manufactured by Tracto-Technik, suited to the 80–150 mm pipe sizes being installed, was used to carry out the bursting process.

Each section was able to be replaced in two working days. Stadtwerke engineer Johannes Schuster, who was responsible for the installation operation, said “The expectations we had of the combination of the pipe bursting technique and the ductile iron pipes have been fulfilled.

“Thanks to the uncomplicated laying properties of the Duktus pipes we were able to meet the tight deadlines laid down by the road maintenance authority.

“The trenchless pipe laying technique enabled the amount of trenching work to be reduced by more than 80 per cent. This saved the population of Klagenfurt from about 300 lorry trips across the municipal area and from the nuisance from noise and dust that they would have caused,” Mr Schuster said.

Tracto-Technik said that this project has demonstrated that No-Dig techniques and the use of Duktus pipe systems can save time and money as well as benefit to the environment.