On-Board Pipeline Installation And Fatigue Monitoring System

As subsea pipeline developments continue to move into deep and ultra-deep water locations, there is an increasing need for the accurate prediction of expected pipeline fatigue life. A significant factor that must be considered as part of this process is the accumulated fatigue damage experienced by a pipeline weld during installation, i.e. before commencement of operations.

Previously, the installation-related damage for a pipeline could only be estimated onshore using appropriate finite element models and assumed environmental loadings. The drawback of this traditional approach is that it often results in an over-conservative value for the predicted installation fatigue damage sustained by the pipeline, and so leads to a reduction in the estimated fatigue life for the pipeline. The primary source of the over-conservatism is the fact that limiting sea-states must be applied as part of the fatigue analysis. Such requirements are often overly stringent given that there is only a small probability of normal lay operations being carried out offshore during such severe sea-states.

Advanced subsea engineering company, MCS, now offers a quantum leap forward with the development of a pipeline installation and fatigue monitoring system for use on-board pipe laying vessels.

This software tool can be used to estimate the fatigue damage suffered by the pipeline during the installation phase based on certain measured inputs (such as vessel position, tension, current profile, sea-state etc.). The primary output from the system is the fraction of the pipeline fatigue life that has been used-up during the installation process. Further secondary outputs from the system include typical installation parameters such as pipe tension, stresses, strains, etc. These outputs are provided in pseudo-real-time based on the latest measured inputs. The system can also provide vessel positioning advice in order to keep the pipeline on-route.

The on-board tool itself is mostly based on the capabilities of the MCS pipeline installation analysis software PipeLay. PipeLay is an integrated engineering tool designed specifically for the analysis of a range of pipeline installation scenarios. The software combines an intuitive Windows™-based Graphical User Interface (GUI) allowing rapid data specification, with powerful analytical capabilities. PipeLay has been developed with significant input from many of the biggest names in the pipeline installation world, including Allseas, Heerema, Saipem, Technip and Petrobras.

From the viewpoint of the user, PipeLay is designed as an engineering tool rather than a finite-element package. Inputs are all in engineering terms and the software automates many of the tasks associated with building complex finite element models, running and post-processing multiple load cases and presenting results in a concise report-ready format. These features contribute to the significant labor-saving potential of the software.