46 CFR § 154.448 - Calculations.

The following calculations for an independent tank type B must be specially approved by the Commandant (CG–ENG):

(a) Plastic deformation, fatigue life, buckling, and crack propagation resulting from static and dynamic loads on the tank and its support.

(b) A three-dimensional analysis of the stress exerted by the hull on the tank, its support, and its keys.

(c) The response of the tank and its support to the vessel's motion and acceleration in irregular waves or calculations from a similar vessel.

(d) A tank buckling analysis considering the maximum construction tolerance.

(e) A finite element analysis using the loads determined under § 154.406.

(f) A fracture mechanics analysis using the loads determined under § 154.406.

(g) The cumulative effects of the fatigue load from the following formula:

$\sum \frac{n_1}{N_1}+\frac{{10}^3}{N_j}\le C_w$

where:

ni = the number of stress cycles at each stress level during the life of the vessel;

Ni = the number of cycles to failure for corresponding stress levels from the Wohler (S-N) curve;

Nj = the number of cycles to failure from the fatigue load by loading and unloading the tank; and

Cw = 0.5 or less. A Cw of greater than 0.5 but not exceeding 1.0 may be specially approved by the Commandant (G-MTH).

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