(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]
σL = equivalent primary local membrane stress4
σb = equivalent primary bending stress4
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.
[4] See Appendix A for equivalent stress.
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 |
(b) An independent tank type B designed from plane surfaces must have allowable stresses specially approved by the Commandant (CG-ENG).
[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]