(e-Book version)Need: The original criterion for assessing the remaining strength of corroded pipe was an outgrowth of extensive work on the effects of longitudinal cracks in pressurized pipes. This work was carried out in the 1960s under sponsorship of PRCI, and it led to the development of the NG-18 surface flaw equation. Subsequently, an effort was begun under the sponsorship of Texas Eastern Transmission Corporation which continued under PRCI sponsorship which involved adapting the surface flaw equation to predicting the remaining strength of corroded pipe. The result of this work was the ASME B31G methodology for evaluating corrosion-caused metal loss in pipelines.
Benefit: Presents analysis of new information on the behavior of corroded pipe, that is 129 new tests involving corroded pipe or samples containing corrosion-simulation defects, to address the validity of RSTRENG. Eighty-two of the new results, when combined with the original 86 results in the database, yield ratios of predicted-to-actual failure pressures that enhance the credibility of RSTRENG.
Result: The thing that appears to be borne out by the new data is the previous observation that some of the early test data involving leaks may have had inadequate documentation. The poorest agreement between RSTRENG predictions and actual failure pressures is still associated with old test results, Only two new leak cases produced results where RSTRENG significantly over estimated the pressure at which the leaks occurred, and in these latest two cases, the over estimates were not nearly as bad as in some of the older tests.
