Reference diameter in calculations of creep strain for steam pipelines

Abstract

Recommended methods of the operational safety assessment of high-pressure steam pipelines include periodic testing that enables determination of creep strain and the creep rate. The accuracy with which the two quantities are determined depends, among others, on the control of the testing conditions and on the assumed reference diameter. The analysis conducted herein concerns the impact of the reference diameter on the results characterizing the creep phenomenon in the pipeline elements (straight sections and bends). In this respect, the initial ovality of the pipeline cross-section is an important parameter. The calculations are made using own results obtained from many years of the steam pipeline creep testing, including tests performed after the expiry of the computational service life.