O-lay is a state-of-the-art disruptive method to install offshore pipeline in a safe way and with a minimum of costs.
The method has following stages: Welding and construction onshore, pulling the pipe in the water supported by floatation devices, spiraling the pipe in a flat mono-layer spiral on the surface of the water while the steel remains in its elastic area (this is the “O” in O-lay) , transportation of the spiral towards the location where it has to be laid. Finally the pipe is laid to the bottom with the help of a simple but specially designed lay barge.
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The laying is done with a type of S-lay where the pipe will leave the barge at an end position or through the center of the barge which will give the barge a better stability and a better floating support.This means that the pipe can be laid deeper with a lighter barge.
When the spiral is made the method makes use of special bending method whereby at certain intervals “points of inflection” are applied. These points are actual end points of anchor lines in the outer circumference of the ‘spiral to be made’. The method can also be used to retrieve pipe from the sea bottom. Instead of the anchor lines, the method makes use of small but powerful boats which are then attached to the pipeline for creating the perfect circle. All boats are attached to a dynamic positioning system that will “coordinate” the whole operation.
With this method pipes can be laid in very shallow water (some meters of depth whereby a special pontoon will be used) and very deep water (several thousands of meters with the aid of a lay barge)
Due to the fact that almost all work is prepared onshore (including welding and inspecting the pipe) the pipe can be installed at a speed of 25 km per day.
[mappress] Subsea World News Staff, April 9, 2013; Image: o-lay.net