Longitudinal Stresses in Pressure Pipeline Design — A Critical Review

Current standards of practice for the design of steel water pipelines do not adequately and consistently address the potential longitudinal stresses in a pipeline, especially for high pressure applications. For steel pipelines, the low-pressure applications are typically designed using AWWA design manual M11 and the high pressure pipelines are typically designed using ASCE manual of practice for steel penstocks. In handling the longitudinal stresses in the pipeline due to internal pressure, both documents consider the Poisson's effect, but do not consider the complete pressure-axial strain relation (often known as Bourdon effect). In contrast, most mechanical piping designers use this effect in calculating stresses using piping analysis software, particularly for high pressure applications. Despite this shortcoming, current design practice for water pipelines has resulted in numerous successful projects. However, there have also been several failures due to excessive longitudinal stresses and poor or inadequate design of welded joints and thrust supports. This paper presents a comparison of current design standards by AWWA, ASCE and ASME and a proposed approach for estimating the longitudinal stresses for the design of buried pressure pipelines. Also, the paper presents a verification of this approach using a published case history of a pipeline failure.