Model - Adding a Line
Once connection points have been defined, it is possible to add a pipeline. To add a line, you click on the Lines folder in the sub-component list and then click on Add, or else double-click on the Lines folder. This opens the Line – Add menu as shown below.
Line – Add Dialog
The drop-down list at the top provides a list of all the Line components currently defined in the project. Once you select the required line, a default name is associated with it, but you can change this name if you want. The Start Point and End Point entries define where the pipe is located within the model. Start Point and End Point are again drop-down lists which will show all of the connection points you defined in the model. Typically you might connect the line to the seabed at one end and to a vessel at the other end. You may leave one end of a pipeline “free” or unattached if you choose to do so, but not both. You may also optionally associate an internal fluid with the line, in which case the internal fluid is associated with all pipe sections within the line. The level to which the internal fluid reaches within the line corresponds to a level above mudline input on the Internal Fluid component, which if not specified defaults to the water depth.
The Sag Option drop-down list allows you to specify where the transition between sagbend and overbend regions for the line occurs. Four options are provided, namely Auto (the default), Manual, Guide and None. If you choose the first option, PipeLay automatically determines the sagbend and overbend regions for you. This is based on the assumption that the curvature in the line changes sign going from overbend to sagbend (usually around the stinger tip region). If you choose Manual, you can manually specify the changeover point using the Sag Distance input (which is only enabled when Manual is selected). The Guide option means the changeover point is assumed to occur at the last (lowest) support on the stinger. Finally, selection of the last, None, option results in no definition of sagbend and overbend regions.
The significance of the division into sagbend and overbend regions will become more apparent when you are working with the Analysis component. For example, you may wish to specify installation criteria (such as bending stress) for a particular region, or to monitor loads/stresses in the respective areas during postprocessing.
The model preview window is automatically updated to continually reflect alterations to the model. A sample model is shown in the figure below, showing a vessel, a line, a connection point on the seabed, and one on the vessel.
Refer to 'Model Best Practice' for the recommended specification of line lengths.
Sample Model Component