Development of B₁ and C₁ Stress Indices for Trunnion Elbow Supports

A finite element analysis of a trunnion elbow support is presented for the case of a long radius elbow subjected to an internal pressure loading. The stress results are categorized as average and linearly varying (through the thickness) stresses. The resulting stresses are then interpreted per Section III of the ASME Boiler and Pressure Vessel Code from which the primary and secondary (B₁ and C₁) pressure stress indices are developed. Several analysis were performed on various structural geometries in order to determine empirical relationships for the stress indices as a function of dimensionless ratios.