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Pipeline Span Estimator

This Span Estimator module will estimate the spans that might form along a connection installed across an uneven seabed. The Span Estimator module uses simple structural engineering equations to calculate the vertical deflection of the connection spanning across uneven seabed. These deflections are used to create a second elevation profile for the connection.

The module will display the new 2D connection profile alongside the seabed bathymetry profile. The User can also elect to have this modified Span Estimator connection profile replace the original connection profile created in the 3D view of the project.

Span Detection

Before the simple structural engineering equations can be deployed on a potential span, the Span Estimator must conduct a search for the potential Span Shoulders along the connection route. The Span Search does a very rapid evaluation of the seabed using a very approximate stiffness model for the connection. The default Shoulder Search Stiffness should be adequate for most steel pipeline connections and those with smaller physical EI values.

Warning

This module is a pre-engineering module to assist you with quick span estimations in the concept phase to accelerate and optimize field layouts. You should always do your final span calculations in your engineering software of choice. Please see the Assumption and Limitation section for more information

Parameteres

Within the Span Estimator module, the user must provide the following data in the corresponding input fields for the selected connection:

Sample Width - The sample width (resolution) input field allows you to set the distance in units between each sample reading on the connection.

Shoulder Search Stiffness - Input the value for the shoulder search stiffness.

Young’s modulus(E) – Input the elastic (Young’s) modulus of the connection material.

The moment of inertia(I) – Input the moment of inertia value of the connection’s cross section geometry (m4).

Submerged Weight(Q) – Input the submerged weight of the connection (Newton per m) .

Span Estimator Commands

The following commands are available:

Estimate Span

Press this button to perform the span estimation calculation on the selected pipeline profile with the set of parameteres defined above.

Export Profile

Allows you to export the span estimation results. Simply press the Export Profile as XYZ button to export the selected profile at any time to an ASCII text file with x,y,z coordinates. This file will be saved in your Download folder.

Assumptions and Limitations

The following assumptions and limitations exist in this release of the Pipeline Span Estimator:

  • Nonlinear geometric effects excluded in the Span Estimator calculations.

  • The impact of any axial forces (i.e. residual lay tension or thermo-mechanical forces) that exist in a pipeline are ignored.

  • Thermal and internal/external pressure effects on the spans of a pipeline connection are ignored.

  • Seabed stiffness is ignored.

  • Friction between the seabed and connection are ignored.

  • Pinned boundary conditions (BC) are assumed at the shoulders of the spans.

  • The overall slope of the seabed at the span shoulder location is only considered in an approximate manner by the Span Estimator.

  • Spans with a span gap between the connection and seabed of less than 0.25 meter will not be reliably estimated.

TERMINOLOGY

The following terminology is used throughout this documentation:

Span Shoulder - The portion of the seabed adjacent to the connection/pipeline span on either end of the span.

Span Gap - The distance between the bottom of the pipeline and the seabed in the span.

Pinned-Slider End Condition (Boundary Condition) - Shown on the RHS of Figure 2. The small lateral motion of the beam under the unform load will be ignored in this Span Estimator.

FIGURE 2

Figure2