(a) External stiffening rings shall be attached to the shell by welding or brazing [see UG 30] Internal stiffening rings need not be attached to the shell when the rings are designed to carry the load[.]
(a) External stiffening rings shall be attached to the shell by welding or brazing [see UG-30] Internal stiffening rings need not be attached to the shell when the rings are designed to carry the loads and adequate means of support is provided to hold the ring in place when subjected to external pressure loads Segments of rings need not be attached when the requirements of UG-29(c) are met.Except as exempted in (f) below, the available moment of inertia of a circumferential stiffening ring shall be not less than that determined by one of the following two formulas: Is p [Do2Ls (t + As / Ls )A] /14 Is′p[Do2Ls (t + As / Ls )A] / 10.9 Is p required moment of inertia of the stiffening ring cross section about its neutral axis parallel to the axis of the shell Is′p required moment of inertia of the combined ringshell cross section about its neutral axis parallel to the axis of the shell I p available moment of inertia of the stiffening ring cross section about its neutral axis parallel to the axis of the shell I ′p available moment of inertia of combined ringshell cross section about its neutral axis parallel to the axis of the shell The nominal shell thickness