ASSESSMENT AND ANALYSIS OF PIPLINE BUCKLES

Geometric anomalies in pipelines are mainly represented by dents, ovalities and buckles. Dents can occur either during pipeline construction or in-service. Buckles and wrinkles may result from cold bending or from loss of stability during offshore pipe-laying. The challenge to the pipeline operator is the identification of those defects that may threaten the future integrity of the pipeline from those defects that are dormant and require no further action. Codes and regulations contain limit state criteria to prevent buckles from happening during construction and in service; however, there is practically no acceptance guidance. In cases when buckles and wrinkles are identified, pipeline operators seek expert opinion. The current industry thinking and research supports the use of advanced assessment techniques (beyond the depth-based rules). These enhanced assessment techniques make use of the detailed profile of a geometry anomaly. Such information is obtained from high-resolution geometry tools and other supporting information on the presence and severity of stress risers from ILI tools. This paper describes how strain-based and stress-based assessment of geometric anomalies can be utilized to assess their significance and need for remediation. Examples are discussed to demonstrate application of the enhanced methods for the assessment of buckles