(a) The type and thickness of material for DOT 412 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). The following Tables I and II identify the ``Specified Minimum Thickness'' values to be employed in that 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--------------------------------------------------------------------------------------------------------------------------------------------------------
Volume capacity (gallons per inch) 10 or less Over 10 to 14 Over 14 to 18 18 and over--------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------------------------------Lading density at 60 F in pounds per 10 lbs Over Over Over 10 lbs Over Over Over 10 lbs Over Over 10 lbs Over Over
gallon................................. and 10 to 13 to 16 lbs and 10 to 13 to 16 lbs and 10 to 13 to and 10 to 13 to
less 13 lbs 16 lbs less 13 lbs 16 lbs less 13 lbs 16 lbs less 13 lbs 16 lbsThickness (inch), steel................. .100 .129 .157 .187 .129 .157 .187 .250 .157 .250 .250 .157 .250 .312Thickness (inch), aluminum.............. .144 .187 .227 .270 .187 .227 .270 .360 .227 .360 .360 .227 .360 .450-------------------------------------------------------------------------------------------------------------------------------------------------------- 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--------------------------------------------------------------------------------------------------------------------------------------------------------
Volume capacity in gallons per inch 10 or less Over 10 to 14 Over 14 to 18 18 and over--------------------------------------------------------------------------------------------------------------------------------------------------------
--------------------------------------------------------------------------------------------------------------------------------------------------------Lading density at 60 F in pounds per 10 lbs Over Over Over 10 lbs Over Over Over 10 lbs Over Over 10 lbs Over Over
gallon................................. and 10 to 13 to 16 lbs and 10 to 13 to 16 lbs and 10 to 13 to and 10 to 13 to
less 13 lbs 16 lbs less 13 lbs 16 lbs less 13 lbs 16 lbs less 13 lbs 16 lbsThickness (steel):
Distances between heads (and
bulkheads baffles and ring
stiffeners when used as tank
reinforcement):
36 in. or less.................. .100 .129 .157 .187 .100 .129 .157 .187 .100 .129 .157 .129 .157 .187
Over 36 in. to 54 inches........ .100 .129 .157 .187 .100 .129 .157 .187 .129 .157 .187 .157 .250 .250
Over 54 in. to 60 inches........ .100 .129 .157 .187 .129 .157 .187 .250 .157 .250 .250 .187 .250 .312Thickness (aluminum):
Distances between heads (and
bulkheads baffles and ring
stiffeners when used as tank
reinforcement):
36 in. or less.................. .144 .187 .227 .270 .144 .187 .227 .270 .144 .187 .227 .187 .227 .270
Over 36 in. to 54 inches........ .144 .187 .227 .270 .144 .187 .227 .270 .187 .227 .270 .157 .360 .360
Over 54 in. to 60 inches........ .144 .187 .227 .270 .187 .227 .270 .360 .227 .360 .360 .270 .360 .450--------------------------------------------------------------------------------------------------------------------------------------------------------
(b) [Reserved] [Amdt. 178-89, 54 FR 25031, June 12, 1989; 54 FR 28750, July 7, 1989, as amended at 55 FR 37065, Sept. 7, 1990; 68 FR 19285, Apr. 18, 2003]