(eBook Version) Need: According to present codes and standards, dents that affect girth welds automatically require repair. However, in cases where dent is shallow and the weld is of good quality, this may be an unnecessarily conservative strategy. A technically defensible method for evaluating the serviceability of welds affected by dents is needed.
Result: The Guidelines for the Assessment of Dents on Welds describes a method for evaluating the serviceability of pipeline girth welds affected by otherwise plain, shallow indentations that are free to reround under pressure. The user makes a cumulative fatigue damage assessment, considering the effects of dent size, weld quality, and the severity of the pipeline operating pressure spectrum. An accompanying diskette provides a rainflow cycle-counting algorithm for use in evaluating the operating pressure spectrum, along with other spreadsheet tools to facilitate the analysis. The serviceability is established by an estimate of the pressure-fatigue life of the weld-dent combination. Examples are presented. Field inspection and repair issues are also discussed.
Benefit: The guidelines can be used to determine whether a dent-weld combination might be safely left in service, or to determine an appropriate interval before a repair should be made. In many cases it will be possible to show that a given dent-weld combination will never be a safety concern in the projected lifetime of the facility.
