Gas Lines in Poland on the Safe Side with HOBAS GRP

A special medium requires special treatment. Gas for instance requires special caution and safety measures. Requirements which are perfectly fulfilled by HOBAS GRP Protective Pipe Systems: They ensure tightness; have a high load capacity and offer a long service life. And, as projects in Poland and in the Czech Republic show, they can be installed by both trenchless and open trench methods.

River Warthe, Poland. A technically, in terms of installation, challenging protective pipeline project was initiated by the company Warszawskie Przedsiębiorstwo BETA in October 1998 in Poland. It comprised the jacking of a twin pipe under the Warta River. Two paralleling lines, 105 and 108 m in length, were executed 50 meters from each other. The 3-m-long microtunnelled HOBAS Jacking Pipes have a diameter of 2047 mm and a wall thickness of 70 mm.

What was the purpose of the undertaking? The to date most modern guided drilling technique and CC-GRP Pipes were employed to overcome an obstacle presented by the Warta river on the construction route of the Yamal-Europe Pipeline, that transports pressurized gas from the Siberian Yamal Penninsula all the way to Germany. In addition to the two steel carrier pipes, 1450 mm in diameter, the GRP pipes should also accommodate a fiber optic cable.

Drilling was conducted in 13 meters depth, 7 meters below the river bed. Despite the large clearance between pipe and river, microtunneling was executed under pressure reaching a level of 1.5 bar due to deep groundwater. The challenge was increased by the diverse geological structure: While the starting pits on one side of the river were surrounded by clay, the receiving pits were situated in in permeable soil (sand and gravel). The contractor was forced to seal the soil around the latter to prevent too much water from running into the pit. If this were not enough, the temperatures fell to as low as -25° degrees which was no problem for HOBAS GRP but made installation arduous for manpower.

In addition to standard jacking pipes, HOBAS supplied also CC-GRP Pipes equipped with nozzles through which a lubricant is pumped between the outer wall of the pipe and the surrounding soil during microtunneling. The low roughness coefficient of HOBAS Pipe Systems alone requires low jacking forces; by adding a lubricant the average force could in this case be lowered to an equivalent of approximately 250 tons.

The job was successfully completed beginning of 1999 meeting all requirements set by the investor, who happily looks back to over 10 years of service.