The concept

Using the Floating Spiral™ method, pipelines are welded and tested onshore, and fitted with floats, to be towed to the installation site. This part of the process has been successfully used many times to install pipelines up to some 10 kilometres in length. For longer lengths of pipe, however, controlling the long, straight, floating pipe becomes prohibitively difficult. Using the Floating Spiral method, we can go beyond that, to pipelines of much greater length.

To this end, the floating pipeline is guided and bent to form a large Floating Spiral. The inner diameter of the Spiral is over five-hundred times the outer diameter of the pipe. Materials such as steel and concrete, as well as other materials used on offshore pipelines allow an elastic bending up to 0.2 percent, so the pipe material remains fully within its elastic limits during the winding process. The resulting Spiral is compact and strong. A pipe with thirty kilometres of length, with a pipe diameter of some sixteen inches, can be spooled to a Spiral with a two-hundred-and-fifty metre outer diameter, while all of the material remains within its elastic limit.

After production of a Spiral, one or two tugboats can easily transport a Floating Spiral over some 1000 km/week. This means that the Spiral can be produced at a great distance from the installation site. Before towing the Spiral to its installation site it may remain for several weeks without great cost at the spiralling site, for example to wait until weather conditions improve.

At the installation site, the Spiral Pipe Tip is pinpointed to the target box, after which the Spiral is gradually unwound as it is towed over the sea to the second target box. The pipe is carefully guided to the seabed. The stress level is small and well controlled.

Not only oil and gas pipelines can be supported as a Floating Spiral; cables for data transmission or electricity can be spiralled equally well.

The Floating Spiral system is protected worldwide by various patents and patent applications. Floating Spiral™ and Spiral Lay™ are registered trademarks of Eurospiraal B.V.