S-lay method is the oldest and the most commonly used method for offshore pipeline installation. This is named as “S-lay” because the shape of the pipe line while being installed looks like S-shape (Figure 1).
Figure 1 – S-Lay Method (Courtesy of Allseas)
While installing pipe line using S-lay method, the pipe line is eased off the stern of a pipeline installation boat as the vessel moves forward. The pipe line is transferred into the sea until it reaches the sea bed which is called the “Touch down poin.t. Each joint of pipe line is welded on the installation vessel and eased off the boat. A stringer located at the stern, whose length can be up to 300 ft., helps supports the pipeline when it is transferred into the sea. Some installation barges can be equipped with an adjustable stringer which is used to control the length of a stringer. This stinger is vulnerable to damage in bad weather.
Figure 2 – S-Lay Diagram
