TPi July 2010

developments products &

3m OD pipes jacked for Poland’s largest wastewater treatment plant

The Czajka wastewater treatment plant is currently being erected on the right bank of the Vistula River in Warsaw, Poland. After its completion, it will treat 80% of the Polish capital’s effluent, and will ensure that no more untreated sewage will harm the flora and fauna of the Vistula – 30% of effluent currently flows directly into the river. As part of the plan, a collector leading to the plant is also under construction. Due to this project’s size, it was broken down into three sections. The first is approximately 5.7km long and realised with Hobas Jacking Pipes OD 3000 (DN 2800), which were installed along the right side of the Vistula, with 1.4km OD 3000 being laid on the left bank. The pipelines meet in the third section, where two DN 1600 lines are inserted in a 4.5m diameter concrete tunnel crossing beneath the Vistula. The consortium of contractors, Hydrobudowa 9, PRG Metro and KWG (all belonging to the PBG Group), has completed 1,600m of the first pipeline section. One of the challenges faced was the high ground water level that lies around 1 to 2m below the surface, and therefore reaches 4 to 8m above the pipe top. Piles by Larsen were set up around the thrust pits and jet-grouting was added to prevent too much water from pouring in. This made it possible to reduce the volume of water being constantly pumped out, from 200- 300m³/h down to 20-30m³/h. Due to the grouted screens, it was also safer to lift the drilling heads in and out of the pits. On the 840m long part of the first section, the pipes were supposed to be jacked from both ends, meeting in the middle. However, the Hobas pipes could be installed so precisely that the section could be jacked with one single drive and from one side only. The smooth and even outer surface and high stiffness (SN 50000 and 64000) of the relatively light-walled Hobas pipes were significant for this success. Despite the small friction and low forces, the contractor followed the project plan and erected an intermediate jacking station every 100m. None of these but the last was put into service – although

even higher jacking forces would have been possible on the Hobas Jacking Pipes: SN 40000 – 15,725 kN; SN 50000 – 17,526 kN; SN 64000 – 19,539 kN. The longest single drive was conducted in two shifts. After its completion, the intermediate stations that were replaced by Hobas Tangential Shafts are reused for different sections of the project. The tunnelling progressed at an average of 3m per hour, with the separator processing 84 tons of soil per hour (42m³/h), and a 3m-long pipe takes roughly half an hour to be jacked. The preparation (disassembly and reassembly of electric cables, slurry pipes and hydraulic hoses) takes 40 to 60 minutes. Considering this, and including breaks for the workers, an average of ten pipes could be put into the ground per day. At this speed it was possible to accomplish the first sections weeks ahead of schedule. Currently, pipes are continuing to be jacked beneath the main road of the district Bia ł o ł ę ka. An open trench would not have been possible here, since the

construction work would have affected traffic on the important six-lane road. The pipeline route runs beneath the middle, the green line, of the road and a single drive over 910m will break the record of the longest single drive in the project. Two curved stretches with 450 and 900m radii are part of the section and are realised with 1m pipes – the angular deflection being well held within the couplings. The 450m radius is implemented over a stretch of 100m and a laser to measure the inclination of the pipeline can only be used on straight sections. In curves this is done with the help of a gyroscope and water level. Extra large pipes require extra large manholes: the large-scale Hobas Tangential Manholes, which incorporate two accesses due to their extreme length, are produced and delivered as convenient modular units that can be easily assembled on-site.

Hobas – Austria info@hobas.com www.hobas.com Aluminium precision drawn small diameter tube

Siddhi Engineers is a manufacturer of aluminium precision drawn small diameter tube used for applications such as cryogenic fuel supply lines for SLV (satellite launch vehicles), automobile air conditioners, condensers, heat exchangers, radiators and ferrules.

The size range is 1 to 110mm OD, with thickness from 0.15 to 10mm. The normal tolerance on OD or ID is ±0.09mm, and can be as close as ±0.02mm. The major alloys processed are 1, 3, 5 and 6, and on special request 2 and 7 series can be processed. Small diameter tube up to 20mm can be supplied in coil form, with a maximum coil weight of 30kg.

Siddhi Group – India siddhiindia@siddhiindia.com www.siddhiindia.com

Siddhi manufactures small diameter tubes from aluminium

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July 2010 Tube Products International