64.17—Minimum tank thickness.
(a)
Except as allowed in paragraph (b) of this section, a tank with a diameter of—
(1)
6 feet or less must have a shell and head of 3/16 inch thickness or more; or
(2)
More than 6 feet must have a shell and head of 1/4 inch thickness or more.
(b)
If the tank has additional framework to guard against accidental puncturing of the tank, the shell and head thickness must be 1/8 inch or more.