For the voestalpine AG in Donawitz, a more than 100 m long HOBAS GRP Pressure Pipeline De 1720 has been installed by means of curved jacking. Despite challenging circumstances, the installation has been successfully completed within 2 months only.
An internationally renowned steel company, voestalpine places highest demands not only on the company’s products, but also on the plant infrastructure. When it turned out that a cooling water pipeline had to be replaced, the company looked for a solution that would match the claimed quality criteria and challenging conditions on site. The installation had to be implemented in limited space, with a trenchless method, and in a curve. The new pipeline was to pass beneath a road and some rails, past old foundations and pipelines underground, and further obstacles along the pipeline route had to be expected.
Since the soil did not contain any groundwater, it was decided to realize the curved trenchless installation with open shield tunneling technology. This would allow for a flexible approach to all sorts of challenges along the planned pipeline route. In terms of an adequate top-quality pipe material, voestalpine found what they required at HOBAS. Thanks to their small outside diameter in relation to their inside diameter, HOBAS Jacking Pipes are in fact ideally suited for restricted space conditions, featuring a low weight at maximum compressive strength. A smaller outer diameter requires a smaller borehole, which in turn means less soil to excavate and dispose of.
Another significant advantage concerns the fact that the pipes’ smooth outside surface ensures low friction and resistance during jacking and whenever jacking is (re-)initiated, for instance after standstill periods. In view of the partly unforeseeable soil conditions and necessary adaptations in the course of tunneling works, this was an essential benefit. Thanks to the elasticity of the GRP material, allowing for an optimal transmission of jacking forces without timber packing rings and a high steering precision, HOBAS Jacking Pipes are also ideal for curved trenchless installations.
In early 2016, more than 100 m centrifugally cast HOBAS GRP Pressure Jacking Pipes in 2 m length, with a stiffness of 100000 N/m² and a pressure class of PN 6, were delivered to the voestalpine AG in Donawitz. The construction companies Max Bögl and Hinteregger & Söhne successfully completed the open shield jacking installation, including a curve with a www.hobas.com radius of 300 m, within two months’ time. With an expected lifetime of up to 100 years, the HOBAS Cooling Water Pipes now ensure a reliable and successful service of the steel plant.
Project data at a glance
Year of construction 2016
Construction time 2 months
Total length of pipeline ~105 m
Diameter De 1720
Pressure class PN 6
Stiffness class SN 100000
Application Cooling water pipeline for steel plant
Client voestalpine AG
Installation method Open shield tunneling
Contractors Max Bögl (Germany), G. Hinteregger & Söhne Baugesellschaft m.b.H (Austria)
·Low friction during tunneling thanks to smooth outside pipe surface
· Small outside in relation to inside diameter resulting in installation flexibility
· Low weight and less excavation material
· Optimal transmission of jacking forces and high steering precision in curved trenchless installations
· High compressive strength
· Very long service life