Low Stress Liquid Pipeline Exemption Issues

PHMSA has recently assessed a penalty against a liquid pipeline operator who claimed the “low stress piping” exemption for delivery pipeline segments at the end of a transmission pipeline system. Even though the pipeline segments were located downstream of a delivery facility, individually operated at low stress, and could be operated independently from the remainder of the upstream pipeline system, PHMSA found that “each of the pipeline segments are a part of a larger system, serving either to introduce products into the system or take products from it. Low-stress pipeline means a hazardous liquid pipeline that is operated in its entirety at a stress level of 20 percent or less of the SMYS of the line pipe, 49 C.F.R. §195.2. I find that at least some parts of Respondent’s 14 inch pipeline system operated at a stress level in excess of 20 percent SMYS and therefore, the two delivery pipeline segments are not a “low stress pipeline” as defined in 49 CFR §195.2.”

Operators should evaluate their liquid pipeline systems to ensure that they fully understand the implications of the “low stress” piping exemption for any delivery and/or origination pipelines that might be considered to be part of a larger, non-low-stress system.