(a) The allowable stresses for an independent tank type A must:

(1) For tank web frames, stringers, or girders of carbon manganese steel or aluminum alloys, meet σB/2.66 or σY/1.33, whichever is less; and

(2) For other materials, be specially approved by the Commandant (CG-ENG).

(b) A greater allowable stress than required in paragraph (a)(1) of this section may be specially approved by the Commandant (CG-ENG) if the equivalent stress (σc) is calculated from the formula in appendix A of this part.

(c) Tank plating must meet the American Bureau of Shipping's deep tank standards, for an internal pressure head that meets §154.439(a), published in “Rules for Building and Classing Steel Vessels”, 1981.

[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983; CGD 77-069, 52 FR 31630, Aug. 21, 1987]