Local Stresses in Nozzles in Shells and Formed Heads from External Loads
|Publication Date:||26 June 2015|
This report contains recommendations and supporting data for rules to compute local stresses in nozzles in shells and formed heads due to external loads and pressure. This report is the outcome of an ASME STLLC Research Project No. 07-10 on Nozzle Design Rules (Project No. 07-10). These rules follow the general format used in Part 4 of ASME Boiler and Pressure Vessel Code Section VIII-Rules for Construction of Pressure Vessels Division 2-Alternative Rules (BPVC VIII Section 2).
This report is also considered a continuation of the work done by Paulin Research Group (PRG) for ASME ST-LLC on Research Project No. 07-02, titled "Stress Intensity Factor and K-Factor Alignment for Metallic Pipes" . That research project objective was to align stress intensification and flexibility factors for metallic pipe used in ASME's Pressure Piping Codes (B31) and BPVC Section III-Rules for Construction of Nuclear Facility Components-Division 1-Subsection NC-Class 2 Component and BPVC Section IIIRules for Constructions of Nuclear Facility Components-Division 1-Subsection ND-Class 3 Components. The results were published as "STP-PT-073: Stress Intensity Factor and K-Factor Alignment for Metallic Pipes". Information contained in numerous Welding Research Council, Inc.'s bulletins are also heavily referenced, most notably WRC 497 .
A large series of finite element runs have been performed, following recommended modeling procedures in WRC 497 , BPVC VIII-Section 2 Annex 5.A , and EPRI 110996 , to extend the parameter ranges and geometries evaluated in WRC Bulletins 107 , 297  and 497 .
Comparisons of regressions and results in WRC 497  and TR 110996  are performed to validate the finite element approach, the parameter range limitations, and the signed maximum error approaches discussed in Appendix 1. Appendix 2 contains the recommended rules and supporting tables. Appendix 3 contains result tables for each of the over 24,000 finite element runs.
The rules in Appendix 2 are intended to provide conservative and consistent guidelines in a broad parameter range for nozzles in vessel shells and formed heads for branch to vessel diameter ratios less than 0.7. Part 5 Rules for Design by Analysis of BPVC VIII-Section 2 are recommended when less conservative results are needed or when other geometries must be considered.