Technical Report on Capabilities of API Flanges Under Combinations of Load

This technical report presents the results of analysis work done in to establish the load capacity of all flanges give in the April 1986 editions of API 6A and API 6AB. A total of 69 different geometries were analyzed initially. The various loads considered were bolt makeup (preload), internal pressure, tension, and bending moment. All flanges were analyzed with an axisymmetric finite model for each of the four load cases. A post-processor program was written to calculate the maximum moment capacity for various levels of pressure and tension, based on linear superposition of results. Three different criteria were used to establish the maximum moment: 1. ASME Section VIII, Division 2 allowable stress categories for the flange with the basic membrane stress allowable established by API; 2. Allowable bolt stresses as established by API; and, 3. Loss of preload on the ring joint. The results of this post-processing are presented in plots of pressure vs. allowable moment for variou