Modern inspection techniques and efforts have led to the identification of pipe flaws. Many of these have existed within the body of the pipe of the welds since original construction. The pipeline integrity profession may have a need to analyze these defects and evaluate the potential for growth or deleterious effects.
The most important concern is the potential to grow and or cause future integrity concerns. A critical engineering review and analysis should begin with a review of the pipe data, steel specification and chemistry, construction history, operational history. In many cases, it will be reasonable to conclude that certain families, groups or types of flaws are sub-critical and have an operational history that shows that they have not grown over time. If a flaw can be shown to date from the original construction and has survived the years of operation of the pipe, and no history of failure can be identified with a cause originating from this type of defect, then a prudent evaluation could conclude that such flaws are sub-critical.
Flaws which can be assumed to grow over time are a matter of greater concern. Sharp, crack like flaws are certainly a concern. The critical crack length can often be determined via traditional analysis of the pipeline steel, chemistry and mechanical properties.
Restraint of a flaw or defect should always be considered. At a minimum, any restrain will slow propagation and growth and provide additional caution and security while the specific issues can be monitored or investigated. New technologies may provide the ability to measure growth over time, and thus provide data for additional assessments of analysis. Restraint will provide a slower growth rate (if any growth existed). Restraint will provide an increase in the critical flaw length that can exist within the pipe without being detrimental to integrity.
More on Particular Types of Flaws:
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