1. (a) An independent tank type B designed from bodies of revolution must have allowable stresses ³ determined by the following formulae:

   σm≤f

   σL≤1.5 f

   σb≤1.5 F

   σL + σb≤1.5 F

   σm + σb≤1.5 F

   where: σm = equivalent primary general membrane stress ^{4 4} See Appendix A for equivalent stress. σL = equivalent primary local membrane stress ⁴ σb = equivalent primary bending stress ⁴ f = the lesser of (σB/A) or (σY/B) F = the lesser of (σB/C) or (σY/D) A, B, C, and D = stress factors in Table 2.

   Table 2—Values for Stress Factors

   	Nickel steel and carbon manganese steel values	Austenitic steel values	Aluminum alloy values
   Stress factors:
   A	4.0	4.0	4.0
   B	2.0	1.6	1.5
   C	3.0	3.0	3.0
   D	1.5	1.5	1.5

2. (b) An independent tank type B designed from plane surfaces must have allowable stresses specially approved by the Commandant (CG-ENG).

³ See Appendix B for stress analyses definitions.

[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]