O-lay

O-lay is a concept for a methodology for installation of submarine pipelines.
The method is a combination of the S-lay method with the pipe being supplied from a large storage of pipeline that is floating in front of the barge that installs the pipe on the sea floor.
The idea is that applying the O-lay methodology will install offshore pipeline faster, and depending on the type of post weld treatment has been given, improve the quality of the installed pipe (specifically the orbital welding quality and the roundness of the pipe) and due to the fast installation the method is more cost effective than traditional methods like traditional S-lay and J-lay.
With this technology it is possible to install concrete coated pipe. Pipe diameters can range from 3" till 32".
With the O-lay method the pipe is being welded onshore in a so called "spool base".
When the pipe has sufficient length it will be pulled in the sea and if needed kept afloat supported by floaters. The pipe will then be bend in its elastic area to form a circle. When the first circle is formed using inflection lines the following circles will follow the outside of the first circle so forming a spiral floating on the water. To stay within the elastic strain limit of 0,2% the spiral formed will have a diameter of 500 times the pipe diameter. The large diameter of the pipe spiral has an advantage compared to the reel-lay because with reel-lay the pipe diameter is being deformed in the plastic area of the steel first in an oval and later into a round shape again. This causes two times strain hardening in the steel which reduces the plastic deformation potential of the pipe and increases the possibility of a wet buckle.
When the predefined amount of pipe has been spiraled, the spiral will be towed to the installation location were it will be pulled over a lay-barge and installed with the S-lay method.

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