Wrought Tee Intersections Operating in the Creep Range, Part II: Actions to Procure Serviceable Tees

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 addressed the damage mechanisms, identified several common vulnerabilities, and called into question the serviceability of these components for long-term operation. Part II explores the mitigation strategies for new plant or replacement tees. Several actions are detailed that must be incorporated into a robust technical purchase specification to address the shortcomings regarding the complex network of codes and standards to which these tees are typically designed and fabricated. The recommendations presented account for the constraints in the supply chain or the present piping configuration, such as for a replacement tee. Lastly, opportunities are identified for refinement and enhancements to the minimum requirements in existing codes and standards that will be essential to achieving acceptable serviceability in the time-dependent range.