Stress indices for nonradial branch connections subjected to out-of-plane moment loadings

The purpose of the subject paper is to disseminate the results and findings of the Pressure Vessel Research Committee (PVRC) Phase 2 program relative to the development of stress indices for 45 degrees lateral connections under out-of-plane moment loading applied on the branch pipe. The objective of the earlier Phase 1 program was to develop stress indices for lateral connections under three load cases namely, internal pressure, and in-plane moment loadings on the branch and the run pipe (or the vessel). A complete discussion of the results and conclusions of the Phase 1 program and the recommended indices for the design of lateral connections in vessels and piping can be found in WRC Bulletin 301. The purpose of the Phase 2 program described herein is to ascertain the relative magnitudes of the in-plane and out-of-plane moment indices through selected parametric studies and recommend comprehensive C2K2 indices for use with equations in NB-3650, Section III of the ASME code and for the design of nozzles per NB-3338 Stress Index Method. The Phase 2 parametric studies performed on PVRC Models 2 and 4 (d/D=0.5, D/T=10,40) indicate that the out-of-plane moment index could far exceed the in-plane index and the use of in-plane index to envelop the resultant moment in piping analysis could be unconservative. (orig.)