154.447—Allowable stress.

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

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Footnote(s): 3 See Appendix B for stress analyses definitions.

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σm≤ f

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σL≤ 1.5 f

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σb≤ 1.5 F

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σL σb≤ 1.5 F

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σm σb≤ 1.5 F
where:
σm=equivalent primary general membrane stress 4
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
(b) An independent tank type B designed from plane surfaces must have allowable stresses specially approved by the Commandant (CG-522).
[CGD 74-289, 44 FR 26009, May 3, 1979, as amended by CGD 82-063b, 48 FR 4782, Feb. 3, 1983]