Effective protection of underwater pipelines

Project details

The companies Air Liquide, Thyssengas and OGE are among the largest producers and transmission system operators for natural gas in Germany and Europe. For a long time, they used a pipeline bridge with two pipelines over the Rhine-Herne Canal (RHK) in Oberhausen, North Rhine-Westphalia, to transport oxygen and natural gas. As part of the planned new construction and the associated raising of the parallel B223/Konrad-Adenauer-Allee road bridge, the pipelines currently running over a separate pipe bridge will be replaced by a new culvert. The road bridge with a clearance height of 4.50m has been considered a danger point for years, as the usual clearance height is now 5.20m. In the past, there have been repeated collisions with superstructures and height-adjustable steering positions of barges. The new construction of the road bridge means that the clearance height will be 5.25m in future. To protect the gas and oxygen pipelines, Air Liquide, Thyssengas and OGE decided to dismantle the existing pipeline bridge and replace it with culverts underneath the RHK. The new pipelines were laid 2.50m below the riverbed. A particular challenge: due to the importance of the canal as an important federal waterway in the middle of the densely populated Ruhr area, shipping traffic was not to be interrupted during the construction period.

Solution

The Incomat Pipeline Cover (IPC) pipeline protection system was installed as buoyancy protection to counteract the buoyancy that occurs when pipelines are laid below the water level. The innovative concrete coating also acts as protection against mechanical impacts on the pipelines. Due to the different diameters of the pipelines - 300 mm for the oxygen pipeline and 400 mm for the gas pipeline - as well as the accompanying cables and wires, the result was an ‘egg-shaped’ cross-section. As the tender only specified concrete covers with a length of 73m for each pipe, the choice of construction and therefore the thickness of the cover was at the discretion of the contractor. In this case, the decision was made in favour of the IPC system. Incomat concrete mattresses consist of two high-tensile synthetic fabric layers that are connected to each other by regularly arranged spacers or weaves. They serve as textile formwork for the production of constant concrete cross-sections that can be individually and flexibly adapted to complex installation situations, pipe curvatures and different pipe diameters. For the IPC system, the Incomat standard concrete mattress is manufactured into hose elements that correspond to the respective pipe dimensions. On site, these customised IPC units are then placed around the pipe, sealed with factory-fitted industrial zip fasteners and filled with concrete via a filler neck. Prior to the production of the IPC units, the contractor and HUESKER were in close contact in order to optimise the design. In addition to the minimum weight to ensure buoyancy safety, the maximum permissible weight was another critical factor, as the pipeline and IPC were to be lifted and positioned in the sewer with cranes after being filled with concrete. For this reason, a concrete thickness of 10 cm was selected for the 400 mm pipeline and 6 cm for the 300 mm pipeline. The installation and filling of the IPC elements took less than a day for each pipeline. After the concrete had hardened and been inserted into the canal, divers ensured that it was positioned correctly. The work was carried out in two night shifts so that shipping traffic on the canal was not affected

Advantages

Incomat Pipeline Cover protects the new pipelines against buoyancy and mechanical impacts. To this end, the IPC elements were customised precisely to the specific conditions on site. Thanks to the high-precision prefabrication, the IPC system guarantees a constant thickness of the pipe coating. Another advantage is the high degree of flexibility. Thanks to the flexibility of the textile formwork, the pipe cladding adapts easily to the two required bends of the pipework (25° and 45°). The fast and efficient installation of the IPC pipe cladding also proves to be superior to conventional formwork techniques in terms of construction time. In contrast to other methods, no time-consuming formwork assembly and disassembly is required on site. The filling time of an IPC element is just five minutes thanks to the factory-fitted filling spouts.