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Conduit construction

29. March 2022

A spectacular performance: from production and transport through to integration

Gas pipelines need to be repaired or renewed from time to time so that they continue to comply with the standards set by the supervisory authority (the Swiss Federal Pipelines Inspectorate (FPI)). The existing Grosse Moos station in the Seeland region reached this point in 2021. The installation was renewed and relocated by a few metres.

For this purpose, GVM (Gasverbund Mittelland, the regional gas supplier for the Mittelland region) awarded Josef Muff AG the contract to manufacture and install a new valve station that connects two pipelines (DN 400 and DN 200). The production process was carried out on site at Josef Muff AG. The individual components were welded together with accuracy down to the last millimetre and, at the end of the process, the finished product was surface treated, pressure tested and insulated. After one and a half months, on the agreed date, the ready-to-operate station was able to leave the workshop on a special transporter.

Meanwhile, the preparatory work was under way at Grosse Moos. The construction pit was completed and the existing pipelines were exposed. This preparatory work proved to be somewhat more complex than planned. The flooding in summer 2021 led to several complications. Lake Neuchâtel, not far from the construction site, broke its banks and caused flooding in many regions. It was also a case of "land under water" on Josef Muff AG's construction site. But thanks to a clear drainage concept combined with strict nature conservation measures, the site was dried out again in relatively little time and work was resumed.

The valve station, measuring 10×3.6×3.2 metres and weighing 5.5 tonnes, had to be lifted into the pit by a crane once it had arrived at the construction site. Precise working was also essential here because the valve station could no longer be moved once it was unloaded.

 

Delivery of the valve station
The valve station is lifted into the construction pit.

 

One important requirement was to carry out the network renewal without interrupting the gas supply. For this purpose, a temporary bypass consisting of two stopple T-pieces and a bypass pipe had to be installed until the new station could be commissioned. The stopple T-pieces were supplied and welded into position by T. D. Williamson (TDW), and then JMAG prepared the bypass pipe. Only a few companies in the whole of Europe can manufacture a bypass of this sort. T. D. Williamson is a Belgian company that specialises in gas and oil pipeline construction.

 

Welding work
Welding work

 

The last and most sensitive phase was the "tie-in" or integration. This involved drilling the pressurised gas pipe and inserting the stopples, while operation was maintained temporarily via the bypass pipe (DN 300). Following various rounds of tests and approval from the FPI, the existing pipeline could finally be cut and the new valve station was integrated into the section. After four guarantee seams had been welded and the ultrasound and X-ray inspections had been passed, the points were insulated and the new valve station could be commissioned.

Josef Muff AG thanks all parties involved for collaborating so well to execute the project smoothly and for their trust.

 

Project data

Client
GVM Gasverbund Mittelland AG, Anke Wölflinger

Construction management
B+S AG, Pascal Hagmann, Adrian Wasem

Project Manager
Josef Muff AG, Markus Hartmann

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