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18 DECEMBER 2016 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 55, NO. 12 MATERIAL MATTERS Continued f rom page 17 operations and maintenance plans mov- ing forward. One of the most signif icant areas of change that will have far-reach- ing impacts on owners and operators focuses on M AOP and pipeline material verif ication. When approaching M AOP validation, Thayer breaks it into a two-part process. The f irst step is materials validation as part of 49 CFR Part 192. 2 For this, a design formula is used that accounts for the pipeline's specif ied minimum yield strength (SM YS), wall thickness, and diameter multiplied by the class location factor, which is based on population den- sity and the number of residents living within close proximity of the pipeline. Operators need to verif y their records are traceable, verif iable, and complete. For the second step, hydrostatic testing or other approved methods must be used to validate the lengths of pipe that have missing information. "During the f irst step we go through the records to identif y gaps, and show that the parameters used in the design formula were accurate and support the pipeline's current M AOP," says Thayer. "The second step is really about proving the pipe through a PHMSA-approved method, the most common of which is hydrostatic testing." Currently, pipelines that were installed before 1970 can rely upon a grandfather clause that allows operation of the pipeline at the highest pressure in the f ive years prior to 1970 without hydro- static test records. In the NPR M, it is rec- ommended that the grandfather clause be eliminated. According to PHMSA, about 60% of natural gas transmission pipeline mileage was installed prior to 1970. "The operating pressures that these pipelines are operating at under the grandfather clause may not have ever been substantiated," says Thayer. "If that clause disappears, as PHMSA is recom- mending, it will affect a large number of owners and operators who are going to need to prove these pipelines through hydrostatic testing or other methods approved by PHMSA." Another change recommended is the def inition of MCAs. Pipelines in the newly def ined MCAs would be required to have complete integrity assessments in addi- tion to those for HCAs, which are cur- rently subject to comprehensive IM regu- lations, and are def ined as pipeline segments with 20 or more buildings intended for occupancy within the impact radius of the pipeline (which is calculated based on the pipeline's diameter and M AOP). MCAs would be calculated using the same formula except the threshold would be f ive buildings rather than 20. According to the NPR M, the intention is that any pipeline location where people are normally expected to be located would be afforded extra safety protec- tions. This would include periodic