Assembling the Pipeline Stack-Up
The pipeline model in this example is comprised of a single pipe section connected to a very short section (initially at least) of cable, with a pullhead at the intersection. More complex pipelines could contain several pipe sections as well as other ancillary components. The Line component allows you to combine as many individual sub components as you need to define your pipeline. This arrangement of sub-components is often referred to as a “stack-up”.
Create a Line component by first selecting the Line folder and then right-clicking and selecting New > Line > Line. Rename this component to Pipeline.
The Component View for the empty Line component is shown in the figure below.
Line Component View
Various components which have been previously defined may now be added to the stack-up to specify the pipeline configuration. In this case, you need to add the cable, the pullhead and the pipe section that you already defined. The Add Component button near the top of the Component View adds a section of the type listed in the Component Type drop-down list to its left. Firstly, select Cable from the list as shown in the figure below.
Component Type List
Pressing the Add Component button then brings up the list-type dialog shown in the figure below. Select the relevant component, Winch Cable, from the list of Cable components (only one should available for selection if you have been following this example exactly), input zero for the cable length, and press OK to confirm. Winch Cable then appears in the stack-up.
Add Cable Dialog
Note that although the cable has zero length as you have just specified it, it is important to include it in the pipeline stack-up. In the second and subsequent stages of the analysis, the length of cable will be increased, while the vessel is being offset, to simulate the abandonment process. This is further described in ‘Running the Installation Stages’.
To add the pullhead, select Ancillary from the Component Type drop-down list, press the Add Component button, select Pullhead from the list, and press OK to confirm. Pullhead then appears in the stack-up above the cable.
In a very similar way, to add the pipe section, first select Pipe Section from the Component Type drop-down list. Press the Add Component button, select Pipe from the list, enter the length of 800 meters and press OK to confirm. Pipe then appears in the stack-up.
The specification of the Line component is now complete. The resulting stack-up is shown in the figure below.
Completed Line Component
Note that the order in which the components appear in the stack-up is important. As you have added the components in the order cable-ancillary-pipe, the cable is at the end of the line while the pipe is at the start. This is because newly added components appear above the currently selected component in the stack up list. However, note that you can reorder the stack-up list at any time by using the and buttons on the right-hand side of the component view. The significance of the ordering of components becomes apparent when the line start and end points are defined in the model. For example, in the case of this stack-up, if you intend to have the pipe resting on the seabed then you must ensure that the start point in the model is also on the seabed.