Hydraulic burst lining enables pipe renovation in Poland

WARSAW, Aug. 30, 2007 -- In the old historical part of Warsaw in Poland, a ND 400 mm clay pipe required replacement over a length of 30 m. Inspection of the mains by the water and sewerage company in Warsaw showed regular sand on the bottom of the mains, so that it was apparent that the main was fractured and bits and pieces had fallen to the bottom of the pipe. This presented a permanent problem of undercarving of the road surface -- an imminent danger to the public. To verify the problem, an inspection of the pipe by camera was planned but could not take place because the camera simply could not overcome the sand and other debris lying on the bottom of the pipe.

The Warsaw water and sewerage company therefore decided to replace the section of the main completely -- but to find a trenchless way because the pipe replacement using an open trench method at a depth of 6 m would have created enormous costs coupled with a high degree of traffic disturbance. Due to the density of the road circulation, it was impossible to close down traffic on that road -- even to find an alternative route via neighboring roads was ruled out. The city expected complete traffic chaos and did not allow any open trenching solutions to the problem.

The only alternative was found in a hydraulic burst lining procedure -- not only from the handling perspective, but also because the inner diameter of the main and the flow were not to be decreased.

Using the hydraulically operated Grundoburst systems, after the push-in process of the QuickLock rods into the target pit or into the target manhole to renew the pressure or sewage pipes (Static Burstlining), the guiding caliber is exchanged against a roller blade with guiding cone and expander as well as the attached new pipe. Assembly is very simple. A link piece makes the connection of the pipe lengths easier and guides them at the required radius. When pulling the rods back, the old pipe is fractured by the roller blade running at the front.

The roller blade cuts grey cast iron pipes, asbestos, plastic, concrete and stoneware pipes, which are then replaced by PVC/HDPE long or short pipes. Contrary to the standard bursting heads, the roller blades can cut open even the most difficult to destroy materials, such as steel pipes and ductile cast iron pipes with connection sockets and repair sockets.

On the Warsaw site, the city turned to contractor JT Zaklad Budowy Gazociagow using a Grundoburst, Type 1250 G with 125 tons of pull-back (produced by Tracto-Technik D-57368 Lennestadt).

When the site preparations were made, the sandy soil around the main, coupled with a high level of the groundwater, required a well-prepared starting pit. Additionally and to complicate matters, working space was restricted because of an existing ND 800 cast iron water main found over the suggested working pit.

The main to be replaced (ND 400 clay pipe) ended in a collector, made from brick, of 2 m height and 1.20 m width. Due to these further space restrictions, the pipes to be installed from inside the collector could not be the usual butt-fused long HD-PE pipes. Short-length pipe modules had to be selected, made from polypropylene PP-HM OD 450 for this particular application.

The only possibility for entry into the collector was positioned about 100 m away from the suggested pipe replacement. Therefore the contractor was looking at a set of tooling that was lightweight and could be easily transported to the site inside the collector. What he found in the Tracto-Technik equipment was the Burstfix, a tensioning device to connect short-module pipes to form a solid pipe during pipe bursting applications.

The Burstfix tensioning system is operated with a portable hydraulic power unit -- the functions are operated with a remote control. The indicated pressure allows itself to be converted into the occurring (permissible) thrust force.

On the Warsaw site, once the preparations were done, the short pipes connected and the equipment in place, it took barely 3 working hours to replace the old pipe with the new PP-HM OD 450 pipe. With the friction on the new pipe increasing during the pipe pulling, a pulling force of up to 80 tons was required, showing that the choice of the Grundoburst 1250G with 125 tons of thrust had been the right decision. A replacement was done virtually unnoticed by the general public, underground, and without traffic disruption.

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