Page 36: of Offshore Engineer Magazine (Nov/Dec 2014)

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ASSET INTEGRITY MANAGEMENT

The bigger picture

Proving that riser life can be extended involves more than dem- onstrating the fatigue life of the pipe through analysis. Cathodic protection systems, coating systems and fexjoints need verifca- tion that they are operating as designed. The life extension of the mounting structure (which is part of the hull, and therefore subject to corrosion, overstress and fatigue) also requires verif- cation. If the analysis predicts that a life extension assessment is not feasible, then other approaches can be taken.

Monitoring of riser motions can be used to determine the actual riser response to a particular environment. The fnite element analysis is typically conservative, and having actual measured data allows better calibration of the analysis model.

However, the most important item of any life extension assess- ment is the availability of past design data, knowing the current condition of the component and operational data. This informa- tion is key to more confdent assumptions and reduced conser- vatism in the engineering models.

Motion loggers installed on a riser help assess fatigue.

Integrity management (IM) as a process the metocean criteria for use in assessing existing OCS plat- One of the many advantages provided by a long-term IM program is the ready availability of condition assessment data for an SCR. An forms and related structures. Metocean changes such as this

IM process by defnition requires the periodic condition assess- affect the expected loading on the riser system and must also be ment of the equipment with a few examples described below: accounted for in life extension assessments. • A design, fabrication, installation and operations dossier (DFIO)

Further examples of changes in design criteria include unex- is a gathering of the reports, drawings, and assessments completed pected souring of the well or increased pressures and tempera- on a SCR through the life. The DFIO discusses each component, tures due to a newly drilled tieback, and changes in analytical along with an exhaustive listing of documentation related to the methods used.

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