Vessel - Stinger, Supports & Motions
To associate a stinger with the vessel, you select the relevant Stinger component from the Stinger drop-down list. The options combo provides a list of all the Stinger components currently defined in the project. Once a Stinger component has been selected, the Location button becomes enabled. You use this dialog you to define the location of a point known as the stinger origin. This point is the origin of a local stinger axis system which is used to define the locations of all of other components that are referenced by the Stinger, specifically supports and stinger sections. Note that as with all locations defined on the vessel, the stinger origin location is specified in local vessel co-ordinates.
Typically, the stinger is positioned over the vessel stern, and so is aligned with the local negative surge axis of the vessel. However, you may optionally specify that the stinger is not aligned with the vessel surge axis, and a Stinger Angle input on the Location dialog accommodates this.
To position supports on the vessel deck, you click on the Support Locations button. This opens the dialog as shown in the figure below, allowing you to define the support locations and the type of support provided.
Vessel - Support Locations Dialog
The drop-down list in the first column provides a list of all the Support and Tensioner components currently defined in the project. To add a new support, you select the required Support or Tensioner component and specify its location. These co-ordinates are again specified in the local vessel axis system. The orientation of a support with respect to the horizontal is defined by the Angle entry.
You may optionally offset a support away from its normal location using the Fine Tune Offset and Fine Tune Direction entries. This allows you to examine the effect of a change in support position, while still displaying the original support location. Both entries are optional. The Fine Tune Offset defaults to [CALCULATED] and the Fine Tune Direction defaults to -90º with respect to the support’s Angle. A Max. Offset and Min. Offset may also be optionally specified. These two entries are only relevant if the Fine Tune Offset entry is set to [CALCULATED]. They correspond to the maximum and minimum Fine Tune Offset limits that you wish to apply to the support. The default calculation of support offsets is discussed over subsequent paragraphs.
An option is available to instruct the user interface to fine tune support elevations to achieve specific pipe radii of curvature. This is done through the Radii of Curvature dialog which is shown in the figure below.
Vessel - Radii of Curvature Dialog
In the Radii of Curvature dialog the user can specify the bend radius they wish the user interface to achieve at various points along the pipe. These entries are input under the Radius of Curvature column; all entries here must be positive and non-zero. The boundary/tangent points between two areas of different pipe curvature are defined in the Y Coordinate column; this entry is local to the Vessel axis system and is mandatory for all Radius of Curvature entries specified. For multiple Radii of Curvature the coordinates are to be in descending order. The final column allows you to instruct the analysis engine to maintain the curvatures achieved by the user interface during a static analysis by running a Support Elevation Optimisation step; the default is Yes and the significance of this input is explained shortly.
Please note that the Radii of Curvature are also to be applied to supports on any associated Articulated S-Lay or Rigid S-Lay type Stinger component using the Explicitly Defined or Hinged configuration where the Fine Tune Offset is set to [CALCULATED].
If the Fine Tune Offset is left as [CALCULATED] in the Support Locations dialog, then the offset value is to be calculated by the user interface based on the data specified in the Radii of Curvature dialog. If no Radii of Curvature data is specified then the calculated offsets are to be given a zero value. All specified Radius of Curvature values are to apply to supports on the stern side of the associated Y Coordinate until a new lower Y Coordinate is encountered after which the new Radius of Curvature is to be applied. If the Y Coordinate for the first Radius of Curvature input is greater than the Y Coordinate for the most forward support on the Vessel then the first boundary/tangent point is to switch back to the most forward support and the first Radius of Curvature is to take effect on the stern side of this support.
The Fine Tune Offset is applied in a direction parallel to the Fine Tune Direction entry. If a support cannot achieve the specified radius of curvature by being offset along its’ Fine Tune Direction, then the [CALCULATED] Fine Tune Offset for the support is set to zero. Similarly, any supports on the forward side of the first boundary/tangent point are to be assumed fixed and so the [CALCULATED] Fine Tune Offset for these supports is a zero value. If you wish to review the offsets calculated/applied by the user interface then a summary of the support data can be obtained via the Support Data button on the Model component or on the Installations Tab of the Analysis component.
Once the user interface has achieved the specified pipe radii of curvature and an analysis is run, you may find the bend radius at the supports differ to what was specified in the Radii of Curvature dialog. This is because under tensile loading the pipe tends to straighten in the spans between the supports and so the profile it adopts is somewhat more piecewise linear rather than curved. The net effect of this is that you get a concentration of curvature at the supports themselves, which could in theory be higher than the curvature specified. To avoid this happening Analysis Optimisation should be set to Yes. This instructs the analysis engine to carry out a Support Elevation Optimisation step during the static analysis procedure which ensures the specified radii of curvature are maintained even after the pipe has undergone significant loading.
The Support Elevation Optimisation step works by constantly monitoring the pipe curvature at the supports and adjusting their elevations in order to ensure the curvatures specified by the user are maintained regardless of how complex the pipeline profile is in reality. Once a Support Elevation Optimisation step has ran successfully, a summary of the support movements is provided in the Support_Data.csv file. This file contains a summary of the supports’ movement as carried out by the user interface and the analysis engine. It is accessible via the View Support Data button on the Results tab of the Analysis component.
See Technical Note 8 for more information on the calculation of fine tune offsets.
To associate vessel motions with the vessel, you use the Vessel Motions drop-down list at the bottom of the Vessel component. This allows you to select the Vessel Motion component you want from all of the Vessel Motion components that are currently defined in the project.