PR-214-153739-R01 ERW Fatigue Life Integrity Management Improvement-Phase III

While the general fracture mechanics methodology for calculating fatigue lives is well documented and validated, its application in the definition of pipeline system fatigue lives have differed from field experience. The source and magnitude of the conservatism inherent in the calculated fatigue life estimates are a concern when establishing integrity management programs. Of particular interest, are the fatigue life estimates used in the integrity management programs for Electric resistance welding (ERW) pipeline systems that are primarily concerned with pipe wall anomalies oriented along the pipe axis.

In this project, fatigue crack growth rate parameters were generated for pipe body and ERW. Axial flaws of different sizes were machined in pipe body and weld center line of two different pipe geometries and subjected to cyclic pressure tests. Fatigue crack growth rate of the flaws in the full-scale fatigue tests was monitored. The full-scale fatigue tests results were compared to existing codified treatments to quantify the level of conservatism inherent in the current state of practice. Recommendations were provided to enhance the precision and manage conservatism in fatigue crack growth rate calculations used in integrity management.

This report has a related webinar.