I have a situation where an operator wants to use Appendix N5 of B31.8 to verify the minimum yield strength of an existing DOT-regulated line for which there is no documentation. They have a target value in mind and would like to hydro test to an appropriate value to prove that the pipeline remains in the elastic range during pressurization (i.e., Pressure vs. Volume remains linear). The way the Appendix is written, it seems to require pressurizing to the onset of yield as detemined by the deviation of P vs. V from the originally established linear relationship. Is there a specific reason that the code requires pressurization to yield? Testing to a lower stress level and confirming linearity of P-V would seem to me to be conservative. At worst, one could argue the operator is not going to be getting "the most" out of their line because they are using a lower yield strength in their calculations. Am I missing something? Thanks in advance for your help on this.