(a) The type and thickness of material for DOT 407 specification cargo tanks must conform to Sec. 178.345-2, but in no case may the thickness be less than that determined by the minimum thickness requirements in Sec. 178.320(a). Tables I and II identify the specified minimum thickness values to be employed in that the determination:
Table I--Specified 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----------------------------------------------------------------------------------------------------------------
10 or Over 10 Over 14 Over 18 Over 22 Over 26
Volume capacity in gallons per inch less to 14 to 18 to 22 to 26 to 30 Over 30----------------------------------------------------------------------------------------------------------------Thickness (MS)............................ 0.100 0.100 0.115 0.129 0.129 0.143 0.156Thickness (HSLA).......................... 0.100 0.100 0.115 0.129 0.129 0.143 0.156Thickness (SS)............................ 0.100 0.100 0.115 0.129 0.129 0.143 0.156Thickness (AL)............................ 0.160 0.160 0.173 0.187 0.194 0.216 0.237----------------------------------------------------------------------------------------------------------------
Table II--Specified 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----------------------------------------------------------------------------------------------------------------
10 or Over 10 Over 14 Over 18 Over 22 Over 26
Volume capacity in gallons per inch less to 14 to 18 to 22 to 26 to 30 Over 30----------------------------------------------------------------------------------------------------------------Thickness (MS)............................ 0.100 0.100 0.115 0.129 0.129 0.143 0.156Thickness (HSLA).......................... 0.100 0.100 0.115 0.129 0.129 0.143 0.156Thickness (SS)............................ 0.100 0.100 0.115 0.129 0.129 0.143 0.156Thickness (AL)............................ 0.151 0.151 0.160 0.173 0.194 0.216 0.237----------------------------------------------------------------------------------------------------------------
(b) [Reserved] [Amdt. 178-89, 54 FR 25030, June 12, 1989, as amended at 55 FR 37064, Sept. 7, 1990; Amdt. 178-104, 59 FR 49135, Sept. 26, 1994; 68 FR 19285, Apr. 18, 2003]