# 154.447 Allowable stress.
(a) An independent tank type B designed from bodies of revolution must have allowable stresses
<sup>3</sup>
[^] determined by the following formulae:
<sup>3</sup> See Appendix B for stress analyses definitions.
σ<sub>m</sub>≤f
σ<sub>L</sub>≤1.5 f
σ<sub>b</sub>≤1.5 F
σ<sub>L</sub> + σ<sub>b</sub>≤1.5 F
σ<sub>m</sub> + σ<sub>b</sub>≤1.5 F
where:
σ<sub>m</sub> = equivalent primary general membrane stress
<sup>4</sup>
[^]
<sup>4</sup> See Appendix A for equivalent stress.
σ<sub>L</sub> = equivalent primary local membrane stress
<sup>4</sup>
σ<sub>b</sub> = equivalent primary bending stress
<sup>4</sup>
f = the lesser of (σ<sub>B</sub>/A) or (σ<sub>Y</sub>/B)
F = the lesser of (σ<sub>B</sub>/C) or (σ<sub>Y</sub>/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 |
(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]