Creating the spiral
The spiral is created with the help of a central barge which has the capability to stay
in a determined spot due to its dynamic positioning system or applied anchors. This
barge is the a center point (or central mooring system) of the method and will act as a
pivot in a later stage of creating the spiral.
Around this central barge are several small auxiliary boats .
In later stages these boats are used to rotate the spiral .
Pulling the pipe in the water
The pipeline will be pulled in the water past point A as is shown in the picture
First part of the floating spiral being laid.
The dynamically positioned auxiliary boats together with winches on the centre barge perform the initial
bending and rotation of the spiral. The inserted picture shows the central barge that is either dynamically positioned or put in place with anchor lines.
When a sufficient part of the pipeline has been pulled past point A, (more than 2/3 ofthe
length of the circumference of the spiral diameter) the pipe will be connected, at
point A to the centre line and outer anchor line in such a way that the pipeline cannot
move sideways anymore at point A.
Bending the pipeline in its elastic area
The end of the pipeline can now be pushed/pulled by a support boat together with the
auxiliary boats in the direction of the central point in such a way that the pipeline will
be following the line at a predefined radius from the centre point. When the pipeline
will pass point B in above figure. the pipeline will be attached to the 2nd centre and outer
anchor line. This way the pipeline spiral parameters are fixed and the first layer of the
spiral will not become too small and the deformation of the pipeline will stay in the
elastic area due to the restriction applied by the anchor lines in the outer periphery.
The pipeline will be pushed/pulled further with the small motorboats around the centre
point. At point C, D and E the pipe will be attached to the centrelines and to outer
anchor lines in the outer periphery of the spiral to be.
When the pipe reaches point F only the centre line should be attached. From the
moment that the small support boat has brought the length of pipeline in the semi
circumference and the centre lines are attached, the anchor lines in the outer
periphery at A, B en C, D and E can be released . These anchor lines form a
restriction to rotate the pipeline around the centre point.
Forming the spiral
While the tensioner, which is located onshore, is feeding pipe into the system the
pipeline will rotate around the centre point of the spiral, increasing the amount of pipe
that is in the flat floating spiral. This way many layers of pipe can be produced, all
floating in the plane of the surface of the water.
It is possible to create more than 100 km of pipe in one piece while the spiraled floating pipeline is still workable by the boats that created the spiral. When the total length of the pipeline has been created into a floating spiral, the pipeline should be prepared for transport. As is shown in the picture the auxiliary boats are first used to bend and later used to rotate the pipe and form the spiral or floating O.