Pipeline and Hazardous Materials Safety Administration September 25, 2008 – Federal Register Recent Federal Regulation Documents

Recent observations by PHMSA indicate possible inconsistencies in how natural gas transmission pipeline operators assess and repair anomalies, such as corrosion defects, and apply the results of calculations to their decision making for further action. Special permits granted by PHMSA over the past two years prescribe specific assessment and repair procedures for pipelines operating under a class location change and maximum allowable operating pressure special permit. Moreover, recent research indicating that existing methods of predicting the remaining strength of corroded pipe could provide non- conservative results (i.e., the pipe will fail at a pressure lower than that predicted) in some circumstances. Non-conservative results could be obtained even when the dimensions of pipeline anomalies are known with precision. PHMSA is sponsoring a Workshop on Assessment and Repair of Anomalies in Pipelines to allow stakeholders of the pipeline safety community to learn about and discuss these research results, current evaluation practices, and methods to assure pipeline safety. The discussion of current evaluation practices and methods to assure pipeline safety should include: A review of safety factors used to evaluate anomalies when assessing in-line tool and excavation results, review of how outside forces and overpressure may effect anomaly stresses, how ILI tool accuracy is applied to anomaly evaluation, and how anomaly growth rates in assessments are considered.