Pipelines comprised of materials manufactured prior to about 1980 are more likely than those comprised of newer materials to contain manufacturing or transportation-induced defects. These defects may become enlarged and fail in service because of pressure-cycle-induced fatigue crack growth. While such defects do not account for a large number of service failures, they clearly are a potential threat to pipeline integrity. In fact, the current U.S. pipeline integrity management regulations require seam-integrity assessments for certain types of pipe materials that appear to be particularly susceptible to this risk. To manage the risk of failure from pressure-cycle-induced fatigue a pipeline operator may need to carry out periodic seam-integrity assessments via either hydrostatic testing or in-line inspection using a reliable crack-detection tool. The appropriate period for reassessment depends on the sizes and growth rates of potential defects that may still exist (just-surviving defects) after an initial hydrostatic test or in-line inspection. The pressure cycles applied to the pipeline may cause the just-surviving defects to grow at a rate inherent in the material and its environment. Long-established principles can be used to predict the times to failure if the effective crack growth rate is known. A pipeline operator can use these principles to plan timely re-assessments to prevent failures. This paper describes one approach to predicting reassessment intervals. This approach has evolved over a period of more than 10 years. The authors have discovered some pitfalls and blind alleys that can lead to inappropriate predictions. The purpose of the paper is to show that while the well-known and widely available basic principles are sound, their application to pipeline integrity management requires an in-depth understanding of the particular pipeline being subject to assessment.

This report details the work undertaken by the International Gas Union (IGU) Study Group 3.4 during the triennium 2003–2006. The initiative that launched this work came during the 22nd World Gas Conference where it was noticed that use of pipeline incident information often is not fit for purpose. A comparative analysis has been carried out considering the most frequently used and reliable high pressure gas pipeline incident databases. The four main objectives of the analysis were to determine the differences and similarities of existing databases, create a reference model to be used when developing a new pipeline incident database, assess if harmonization of existing databases is possible and to provide recommendations regarding the above.

This document presents an analysis of “Reportable Incidents” on gas transmission and gathering pipelines in the U.S. during the 16-year period from 1985 through 2000 and on liquid pipelines in the U.S. from 1986 through 2000. The reporting format changed after 1985 for the liquid incidents. The purposes of this analysis are to improve the pipeline industry’s understanding of the causes of incidents and their consequences, to monitor trends that may indicate the need for action, and to diagnose potential problems in the database that might be general in nature and to identify areas for potential improvement in the data collection process that can help pipelines address the issue of risk management. After third party, accounting for 27.6 percent of all gas incidents, the next four leading causes of reportable incidents are: internal corrosion 12.8 percent, external corrosion 9.9 percent, incorrect operation 7.0 percent, and miscellaneous 6.8 percent. For the liquid incidents, third party incidents are also the leading cause at 20.5 percent. External corrosion was responsible for 18.5 percent, followed by miscellaneous incidents at 9.9 percent, incorrect operations at 8.6 percent and internal corrosion at 6.2 percent. For natural gas pipelines, it appears the number of third party and external corrosion incidents are decreasing while the number of internal corrosion incidents is increasing slightly. For liquid pipelines, the numbers of incidents attributable to third party damage and internal corrosion have remained relatively constant, while there has been a slight decrease in incidents caused by external corrosion. The consequences of incidents are of great importance in terms of assessing their impact on public safety. The consequences of pipeline failures are expressed in the incident reports in terms of fatalities, injuries, and property damage.