Grundoburst 1250 G in Warsaw, Poland

Oct 30, 2007

In the old historical part of Warsaw in Poland a ND 400 mm clay pipe required replacement over a length of 30m. Inspection of the mains by the Warsaw water and sewerage company showed regular sand on the bottom of the mains, so that it was apparent that the main was fractured and debris was falling to the bottom of the pipe. This presented a permanent problem of road surface subsidence – an imminent danger to the public. The problem could have been confirmed by an internal pipe inspection but this could not take place because the camera simply could not pass through the sand and other debris lying at the bottom of the pipe.

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

The only alternative to solve the problem was found in the hydraulic bursting procedure. Not only from the handling side, but also because the inner diameter of the main and the flow were not to be decreased.

When using the hydraulically operated Grundoburst system, after pushing in the QuickLock rods into the target pit or into the target manhole to renew the pressure or sewage pipes (Static Bursting), the guiding calibre is exchanged for a roller blade with guiding cone and expander as well as the 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 roller blade running at the front fractures the old pipe.

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 authorities turned to contractor JT ZAKLAD BUDOWY GAZOCIAGOW who used a Grundoburst, Type 1250 G with 125 tons of pull-back (produced by: The TT Group).

During the site preparations, the sandy soil around the main, coupled with the high level of the ground water 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 long butt-fused HD-PE pipes, but short-length pipe modules had to be selected, made from polypropylene PP-HM OD 450 for this particular application.

The only place to enter the collector was positioned about 100 m away from the suggested pipe replacement. Therefore the contractor was looking for a set of lightweight tooling that could be easily transported to the site and which would fit inside the collector. What he found in the TT Group 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 used with a portable hydraulic power unit and operated with a remote control. The indicated pressure can be converted into the occurring (permissible) thrust force.

On the Warsaw site, once the preparations were complete, 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 generated, showing that the choice of the GRUNDOBURST 1250G with 125 tons of thrust had been the right decision. The replacement was carried out virtually unnoticed by the general public, using a trenchless technique that did not disrupt the traffic.

The Warsaw water and sewerage company expressed their total satisfaction and have advised the contractor of more sites in the near future.

Further information:
Windsor Road
Bedford MK 42 9SU
Tel: (+44) 1234 342566
Fax: (+44) 1234 352184

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