by Phillip E. Prueter, P.E. / Sep 08, 2016

There have been numerous failures of high-temperature, low chrome piping in the power generation and petrochemical industries.  Several of these failures have been attributed to peaking of longitudinal weld seams.  Generally, local weld peaking occurs during pipe manufacturing due to angular misalignment of the rolled plate. For many piping fabrication standards, no specific tolerance for longitudinal weld seam peaking exists.  Depending on original heat treatment, creep damage progression is known to be accelerated by the mismatch in creep properties of the base metal, weld deposit, and heat affected zone (HAZ).  Local weld seam peaking can induce significant local bending stresses, and for piping components that operate in the creep regime, the presence of local peaking can lead to an increased propensity for creep crack initiation and propagation, and subsequent rupture of the pressure boundary.  Detailed finite element analysis (FEA) coupled with advanced, non-linear creep simulation techniques will be discussed. Such an approach is valuable in estimating the remaining life of low chrome piping and assessing the sensitivity in results to variations in crucial parameters such as operating temperature, peaking magnitude, and pipe heat treatment.  Additionally, commentary on different creep damage failure criteria will be provided.  Simulation techniques such as the ones that will be discussed in this webinar are not only valuable in estimating remaining life of in-service piping, but detailed analysis can be leveraged to establish recommended fabrication tolerances, appropriate inspection practices, and reasonable non-destructive examination (NDE) intervals for in-service high-temperature, low chrome piping systems.

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