Material and thickness of material.

The type and thickness of material for DOT 406 cargo tank motor vehicles must conform to § 178.345-2 of this part, but may in no case be less than that indicated in tables I and II below.

Table I—Minimum Thickness of Heads (or Bulkheads and Baffles When Used as Tank Reinforcement) Using Mild Steel (MS), High Strength Low Alloy Steel (HSLA), Austenitic Stainless Steel (SS) or Aluminum (AL)—Expressed in Decimals of an Inch After Forming Material Volume capacity in gallons per inch of length 14 or less MS HSLA SS AL Over 14 to 23 MS HSLA SS AL Over 23 MS HSLA SS AL Thickness.100.100.160.115.115.173.129.129.187

Table II—Minimum Thickness of Shell Using Mild Steel (MS), High Strength Low Alloy Steel (HSLA), Austenitic Stainless Steel (SS) or Aluminum (AL)—Expressed in Decimals of an Inch After Forming 1 Cargo tank motor vehicle rated capacity (gallons) MS SS/HSLA AL More than 0 to at least 4,500 0.100 0.100 0.151 More than 4,500 to at least 8,000 0.115 0.100 0.160 More than 8,000 to at least 14,000 0.129 0.129 0.173 More than 14,000 0.143 0.143 0.187 1 Maximum distance between bulkheads, baffles, or ring stiffeners shall not exceed 60 inches.

[Amdt. 178-89, 54 FR 25028, June 12, 1989, as amended at 55 FR 37064, Sept. 7, 1990; Amdt. 178-105, 59 FR 55176, Nov. 3, 1994]