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Forgemasters creates emergency gas pipeline repair clamp

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World Pipelines,

Sheffield Forgemasters has delivered two clamp bodies for Oil States each to form a crucial emergency repair back-up for the 1224 km Nord Stream pipeline which runs along the Baltic Sea floor from Vyborg in Russia to Lubmin in Germany.

The hydro-clamp is designed to provide risk mitigation in the event of a breach in a subsea pipeline. Designed by Oil States Industries in Houston, the specialised unit takes subsea engineering design to a new level of expertise.

George Brown, Group Projects Director at SFIL, said: “The Nord Stream clamps are hydraulically operated repair mechanisms, designed to reinforce the Nord Stream Pipeline at any required point along the Baltic Sea floor.

“The size of the forging exceeded the known parameters for the designated material selection and required a new engineering solution to make it possible. Sheffield Forgemasters excels in these realms of manufacture where the practicable realisation of process capability is considered alongside the theoretical metallurgy.

“The clamp comprises of two matched halves, which can be locked around the pipeline in order to stop any leakage. In order to provide the matched pairs of half clamps the forging was produced as a single piece before being cut longitudinally to produce the two halves.

“To achieve this, we worked close to the limits of capable production, starting with a 120 in. dia. ingot, a singular form for the whole clamp was forged, rough machine and heat treated.

“This provided a safe envelope for the finished shape which was then cut along its 22 ft length to produce two forgings which could be independently machined to the tight tolerances required before being finally reassembled and pressure tested.

“With a forged weight of over 200 t, no subsea clamp of this size has ever been produced before and if required, can restore full structural and pressure integrity to the Nord Stream pipeline in the event of a leak or identified weakness.

The unique capability we have at Sheffield Forgemasters, to go from creation of the material to completion of the finish machined pieces, was fundamental to the successful outcome of the clamp manufacture.”

Problems and challenges that occurred throughout production were investigated and resolved with the help of SFIL's in-house R&D resources of RD26, which continues to grow its project team in order to meet the demands for industry led solutions to technological challenges.

The clamps are currently in the testing phase at Oil States in Houston, Texas, before they are shipped to the Nord Stream project where they will be reserved for emergency back-up use.

Nord Stream is the longest subsea pipeline in the world and uses twin pipes which take 27.5 billion m3 of natural gas a year from the Russian continent to the European grid for use in European domestic and business markets.

The pipeline is owned and operated by Nord Stream AG, a conglomerate of Gazprom (51%), Wintershall (15.5%), E.ON Ruhrgas (15.5%), N.V. Nederlandse Gasunie (9%) and GDF Suez (9%).

Edited from source by Stephanie Roker

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