46 CFR 154.172: Contiguous steel hull structure.

(a) Except as allowed in paragraphs (b) and (c) of this section, plates, forgings, forged and rolled fittings, and rolled and forged bars and shapes used in the construction of the contiguous steel hull structure must meet the thickness and steel grade in Table 1 for the temperatures under §§ 154.174(b) and 154.176(b).

(b) for a minimum temperature, determined under §§ 154,174(b) and 154.176(b), below −25 °C (−13 °F), the contiguous steel hull structure must meet § 54.25-10 for that minimum temperature.

(c) If a steel grade that is not listed in Table 1 has the equivalent chemical properties, mechanical properties, and heat treatment of a steel grade that is listed, the steel grade not listed may be specially approved by the Commandant (CG-ENG), for use in the contiguous hull structure.

Table 1—Minimum Temperature, Thickness, and Steel Grades in Contiguous Hull Structures

Minimum temperature Steel thickness Steel 1 grade

0 °C (32 °F) All Standards of the American Bureau of Shipping published in “Rules for Building and Classing Steel Vessels”, 1981

−10 °C (14 °F) T≤112.5 mm (1⁄2 in.) B

12.5<t≤25.5 mm (1 in.) D

>25.5 mm (1 in.) E

−25 °C (−13 °F) t≤112.5 mm (1⁄2 in.) D

>12.5 mm (1⁄2 in.) E

1 Steel grade of the American Bureau of Shipping published in “Rules for Building and Classing Steel Vessels”, 1981.