Abstract
SA-193 B16 studs are more cost effective and more reliable in high temperature equipment applications than B8 studs, however B16 stud applications are currently limited in a significant portion of North American and other places in the world colder climates due to the current −20F (−30C) impact test exemption temperature in ASME Section VIII, B31, and FFS-1. Furthermore, MDMT adjustments are not permitted for studs due to preload [e.g., UCS-66(b)]. ASME BPVC Section VIII Division 1 specifies an impact test exemption temperature for SA-193 B7 of −55F (−48C) for up to 2 ½” (64 mm) studs, whereas SA-193 B16 studs have a higher impact test exemption temperature of −20F (−30C) up to 7” (175 mm) studs.
The similar material and chemical properties of B16 and B7 studs (both SA-193) give reason to believe that both stud types should exhibit similar fracture toughness properties at low temperatures. Two-phase research and testing programs have been running for the past few years. The initial research and testing were performed on one sample material to determine if the MDMT for B16 and B7 studs was similar at low temperatures for small diameters. Part of this feasibility study involved developing impact test transition curves through Charpy impact testing, as well as fracture toughness testing, which will be detailed in this paper.
Then the second part of the program was about statistical sampling with material sourced from around the world.