Session: MF-05-01 Fitness-For-Service and Failure Assessment-1

Paper Number: 155858

155858 - Wrought Tee Intersections Operating in the Creep Range, Part I: Service Experience and Root Causes 

Abstract: 

Over the last decade hundreds of events in wrought tee intersections designed to ASME B16.9 and stamped as a fitting to A- or SA-234 have been documented by industry. These components are frequently installed in main steam and hot reheat systems, operate in the creep range, are specified to be grade 22, grade 91 or grade 92, and have experienced extensive damage, cracks or leaks in ~40,000 to 150,000 hours of operation. 

Part I of this two-part paper will review several failure case studies to confirm the damage mechanism and identify the contributing factors in the design, operation, fabrication, and metallurgy. Thorough and detailed metallographic observations will be provided for several case studies, and where relevant, the results of destructive mechanical testing. Several key vulnerabilities will be highlighted through the presented case studies to help inform a comprehensive integrated life management strategy that must screen, identify, and assess susceptible tees, and ultimately repair or plan for eventual replacement. The broader activities to address root causes, improve the serviceability of new or replacement tees operating in the time-dependent range, and suggested future actions to improve the minimum requirements in the relevant codes and standards are addressed in Part II.

Presenting Author: John Siefert Electric Power Research Institute

Presenting Author Biography: John graduated from the Ohio State University with a Bachelor’s of Science degree in Welding Engineering in 2008. In 2019 John successfully defended his PhD thesis, awarded by Loughborough University. John has spent the last 14-years working for EPRI in the Materials and Repair Program and now manages its research portfolio. His experiences in welding research are diverse and include the examination of a wide range of materials including creep strength enhanced ferritic materials, advanced stainless steels, nickel-base alloys and dissimilar metal welds, among others. To date, John is the primary or a contributing author to more than 150 manuscripts in his career.

Authors:

John A. Siefert Electric Power Research Institute
Ian J. Perrin Triaxis Power Consulting, LLC
Tom Sambor EPRI