Polyurethane foam makes undersea pipe welding possible

Since April of this year, the crew on the first pipe-laying ship has been working hard on the Baltic Sea, laying the gas lines of the Nord Stream Pipeline Project, which will run between Vyborg, Russia and Greifswald, Germany.

Approximately 200,000 pipes — each measuring 12 metres in length — will be welded together by Swiss-based subsea construction company Allseas Group, calling in turn for 200,000 weld seams to be sheathed. The material selected for the job? Elastopor H, an open-cell polyurethane rigid foam from BASF.

Two years in the making, the weld seam system consists of two liquid components that are mixed together on site using special metering machines and then filled into the hollow space in the sleeve. Subsequently, an exothermal reaction turns the reaction mixture into the actual polyurethane, which is expanded by means of a foaming agent that’s also present in the mixture. “Thanks to its good flow properties, the polyurethane system is quickly and uniformly distributed throughout the hollow space,” BASF said. “In order to prevent the polyurethane rigid foam from being buoyant, it’s configured to be open-celled so that hydrostatic pressure causes it to fill up completely with water.”

Once down on the seabed, the Elastopor H rigid foam also has to be strong enough to withstand contact with the weights used in large dragnets or with the anchors of ships. Tests demonstrated that the foam is able to withstand even higher forces than required without any damage occurring to the steel pipe.

BASF Canada (Mississauga, Ont.); www.basf.ca;1-866-485-2273