PR676-233801-R03 Circumferential Crack Hazard POF Analysis Process

Pipelines that traverse areas of active ground movement may be subject to Tensile Strain Demand (TSD) due to soil-pipe interaction. Independently, the pipe may have locations with reduced Tensile Strain Capacity (TSC) stemming from construction practices or due to pre-existing pipe wall defects, girth weld anomalies, or Circumferential Stress Corrosion Cracking (CSCC). The confluence of elevated TSD and reduced TSC presents a susceptibility to Loss of Containment (LOC) due to circumferential cracking. This study provides a methodology to identify segments and sites with circumferential cracking susceptibility and a Probability of Failure (POF) calculation methodology.

The developed POF calculation draws on NDE-4-24 Framework Deliverable 8, Geohazard Program Considerations, that describes the landslide hazard and scenarios of landslide ground displacement. Likewise, the POF calculation references Framework Deliverable 9, Pipeline Vulnerability Analysis Methodology, for the probabilistic calculation of TSD based on soil-pipe interaction and ground displacement, and vulnerability to circumferential crack LOC taking into consideration the effect of pre-existing circumferential flaws. Validation of the POF calculation is based on an analysis of historical incident case studies as provided in Framework Deliverable 7, Probability of Failure Calculator for Landslides Report.

The overall methodology aligns with the approach defined in Framework Deliverable 2, Pipeline Reliability Thresholds, where reliability thresholds are defined as a function of a risk benchmark and variables that reflect the magnitude of the consequence along the pipeline. Comparison of the POF to a reliability threshold provide a basis for risk-informed circumferential crack management.