DEVELOPMENT OF WELD STRENGTH REDUCTION FACTORS AND WELD JOINT INFLUENCE FACTORS FOR SERVICE IN THE CREEP REGIME AND APPLICATION TO ASME CODES
|Publication Date:||26 June 2017|
This publication was prepared by ASME ST-LLC and sponsored by ASME and EPRI. The project was conducted by EPRI under a cost-sharing agreement with ASME ST-LLC.
Longitudinal seam-welded, high-temperature piping, given its susceptibility to premature failure with sometimes catastrophic consequences, continues to be of concern. In an effort to provide additional safeguards at the construction phase, the ASME Board on Pressure Technology Codes and Standards (BPTCS) formed a project team to address the concern. To develop a consistent set of Code requirements on long seam-welded piping construction, the project team identified specific needs relating to laboratory data, field experience data, and methods for structural evaluation that could be used in developing the safeguards for use in the Boiler and Pressure Vessel Code and the B31 Power Piping Codes. These needs have been defined as (a) weld strength reduction factors that can be considered inherent to the materials and methods of construction; (b) weld joint influence factors that capture specifics of the structure; and (c) guidance for application of the weld strength reduction factor and the weld joint influence factor in design rules. Consistent with these needs as identified in ASME ST-LLC's request for proposal, this document is presented in three separate parts (reports) as follows.
Part 1: Development and Application of Weld Strength Reduction Factors Guideline (Task 1b/3 project report)
This report ties the elements of Parts 2 and 3 into an application guideline. The guideline includes description of a framework for analyzing laboratory data and using the weld joint influence factor development methods. The Part 1 report provides examples of application to two weld/weldment databases for longitudinal seam welds, illustrating the usefulness of the methodology. The examples are for Grade 91 steel that is susceptible to weld heat-affected zone failure, and Grade 22 steel that has and continues to be used in long seam-welded piping construction. The results are compared with current Code rules, literature findings, and experience.
Part 2: Literature Review, Industry Approach, and Data Compilation in Support of WSRF Development (Task 1a project report)
This report includes a compilation of laboratory and experience data on weldments for select materials of common use and interest - carbon steel, low alloy CrMo steels, austenitic stainless steels, Alloy 800/800H, and Grade 91. A critical part of this extensive database development was collecting relevant information not available to the ASME Code committees when allowable stresses were set for some of these materials. Also given in this report is a summary of approaches that have been taken in establishing weld strength reduction factors worldwide.
Part 3: Development of Weld Joint Influence Factors (Task 2 project report)
The report describes an analysis tool to evaluate the creep rupture strength of a weldment relative to that of base metal, benchmarked against select cases of field experience and laboratory component testing. The methodology can be used for calculating weld joint influence factors for any practical combination of materials and weldment geometries in a relatively quick and computationally efficient manner, also allowing for use of relatively simple materials models readily available to designers.
This publication references the original project task reports that have been reproduced here in the three parts as identified above: Part 1-Tasks 1b and 3; Part 2-Task 1a; Part 3-Task 2.
(EPRI is acknowledged for supporting this publication. EPRI conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent, non-profit organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, affordability, health,
STP-PT-077: Development of Weld Strength Reduction Factors and Weld Joint Influence Factors for Service in the Creep Regime and Application to ASME Codes
safety and the environment. EPRI's members represent approximately 90 percent of the electricity generated and delivered in the United States, and international participation extends to more than 30 countries.
Established in 1880, the ASME is a professional not-for-profit organization with more than 135,000 members and volunteers promoting the art, science and practice of mechanical and multidisciplinary engineering and allied sciences. ASME develops codes and standards that enhance public safety, and provides lifelong learning and technical exchange opportunities benefiting the engineering and technology community. Visit (https://www.asme.org
ASME ST-LLC is a not-for-profit Limited Liability Company, with ASME as the sole member, formed in 2004 to carry out work related to new and developing technology. The ASME ST-LLC mission includes meeting the needs of industry and government by providing new standards-related products and services, which advance the application of emerging and newly commercialized science and technology, and providing the research and technology development needed to establish and maintain the technical relevance of codes and standards. Visit (http://asmestllc.org