Section 178.338-5 - Stiffening rings(a) A tank is not required to be provided with stiffening rings, except as prescribed in Section VIII of the ASME Code (IBR, see § 171.7 of this subchapter).(b) If a jacket is evacuated, it must be constructed in compliance with § 178.338-1(f) . Stiffening rings may be used to meet these requirements.Amdt. 178-77, 48 FR 27704, June 16, 1983, as amended at 68 FR 75754, Dec. 31, 2003