Applications Guide for Determining the Yield Strength of In-Service Pipe by Hardness Evaluation: Final Report
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Situations arise where pipe tensile properties may not be sufficiently documented to satisfy regulatory requirements thus requiring an additional effort to obtain the data. This more often occurs in the case of older pipelines where records necessary to document the pipe properties may have been misplaced over time or may even be non-existent for very old pipelines.
In such cases, the operator currently has two methods available according to the requirements of Appendix B of 49 CFR Part 192. One method is to adopt the 24,000 psi yield strength and base the pipeline MAOP on that value. The second method is to implement the provisions that permit yield strength to be determined by tensile testing according to the prescribed criteria. Adopting a maximum allowable operating pressure (MAOP) based on an assumed 24,000 psi yield strength has some immediate utility but often results in reduced pipeline throughput. Otherwise, tensile test coupon removal requires removing the pipeline from service. Neither of these alternatives is an optimal solution when additional pipe yield strength documentation of an operating pipeline is required. Additional methods, preferably non-destructive, are needed to provide a reliable assessment of pipeline yield strength without the need for destructive test methods.