FEA – Dropped Object Assessment

Background

ABAQUS Finite Element Analysis (FEA) software was employed to assess a pipeline’s response to a potential dropped object event which could occur during the course of intervention work for freespan rectification. Proving that pipeline rupture was not a credible event as a consequence to the threat was of particular focus for obtaining environmental regulatory approval for the campaign.

Work Performed by Atteris

Atteris interfaced with the asset operator and installation contractor to establish design data for the construction of the FEA model and development of a case matrix. A draft case matrix was prepared for an optimisation workshop with the objective of bounding the analysis to reduce engineering cost to our client.

It was established through review of the installation procedures that two principal configurations were required to be modelled.

  1. Impact to freespans – assessment of maximum midspan stress and local buckling failure at freespan shoulders.
  2. Impact to pipeline on seabed – assessment of resistance to local buckling failure.

A number of sensitivity cases were identified to support the findings of the study. These included parametric studies such as impactor properties, drop heights, and impact energies.

Benefit

Through the use of FEA modelling, Atteris was able to demonstrate that a loss of containment (rupture) event was not a credible consequence to the threat thus satisfying environmental approvals requirements and saving the operator from having to shutdown operations.

Furthermore, Atteris’ execution strategy and case matrix optimisation reduced engineering effort; proving a greater return on investment for our client.