PIPELINE DEFECT ASSESSMENT USING ASME B31G
ASME B31G is extensively employed as a standard for assessing pipeline defects, primarily for pipelines utilized in the oil and gas industry. This standard provides a straightforward and cautious technique for appraising the residual strength of damaged or corroded pipelines.
The B31G approach relies on a basic stress analysis of a pipeline containing a longitudinal crack or corrosion flaw. This method involves determining the critical flaw size, which is the largest defect size that a pipeline can handle before collapsing under applied stress. The critical flaw size is established by considering the pipeline's diameter, wall thickness, material characteristics, and pressure and temperature during operation.
After establishing the critical flaw size, the actual defect size is evaluated in comparison to the critical flaw size using a dimensionless measure known as the "severity factor." The severity factor is a function of the defect depth-to-wall thickness ratio and the defect angle relative to the pipeline's longitudinal axis. If the severity factor is equal to or less than 1.0, the defect is considered acceptable, and the pipeline can continue operating. If the severity factor exceeds 1.0, the defect is deemed unacceptable, and the pipeline must be repaired or replaced.
It should be noted that the B31G approach is a conservative method and may result in excessively cautious assessments in certain cases. As a result, it is suggested to utilize this method together with other assessment approaches, such as finite element analysis, to obtain a more precise evaluation of pipeline defects.