During the motorway expansion planned by the Hanseatic City of Hamburg for the A26 and A7 autobahns, part of the existing 34-inch mineral oil pipeline had to be relocated. The pipeline of Norddeutsche Oelleitungsgesellschaft m. b. H. (NDO) runs from Wilhelmshaven to the HOLBORN Europa refinery in Hamburg-Moorburg (main nominal diameters of 22″ and 34″).
1000 metres of the new section is currently being laid using the horizontal directional drilling (HDD) method and 450 metres in the open pipe trench. For the continuous pull-in of the pipeline into the HDD borehole, it is necessary to weld the 1000-metre pipeline together in advance, to test it non-destructively, subject it to a pressure test and to wrap it in the area of the weld seams using PE and GRP as additional mechanical protection. This work was carried out 500 metres away from the intake hole on a dyke defence path and was moved using a Unimog roller conveyor and winch. Despite difficult soil conditions, the pipe was pulled to the satisfaction of everyone involved.
Once the pipe string had been pulled in, it was laid in an open pipe trench up to the respective tie-in pits. The necessary adapter pieces (tiers) were manufactured and tested in advance. Due to the groundwater level, the tie-in pits were elaborately constructed with sheet piling and a watertight HDI base.
After the successful overall strength pressure testing, we had a time window of five days in which the existing pipeline had to be drained, cut and tied-in to the newly laid section with the adapter pieces. After final inspection of the guarantee joints and expert approval, the pipeline was put back into operation.
Once the entire pipeline was put back into operation with the new section then integrated, the parts of the old pipeline that remain in the ground were dismantled and dammed.
The project started in May 2020 and is expected to be completed in April 2021. We carried out the project as part of a joint venture.