§179.400-8. Thickness of plates.
49 C.F.R. § 179.400-8
The minimum wall thickness, after forming, of the inner shell and any 2— 1 ellipsoidal head for the inner tank must be that specified in § 179.401-1, or that calculated by the following formula, whichever is greater:
The minimum wall thickness, after forming, of any 3— 1 ellipsoidal head for the inner tank must be that specified in § 179.401-1, or that calculated by the following formula, whichever is greater:
The minimum wall thickness, after forming, of a flanged and dished head for the inner tank must be that specified in § 179.401-1, or that calculated by the following formula, whichever is greater:
The minimum wall thickness, after forming, of the outer jacket shell may not be less than 7/16 inch. The minimum wall thickness, after forming, of the outer jacket heads may not be less than 1/2 inch and they must be made from steel specified in § 179.16(c).
[Reserved]
The annular space is to be evacuated, and the cylindrical portion of the outer jacket between heads, or between stiffening rings if used, must be designed to withstand an external pressure of 37.5 psig (critical collapsing pressure), as determined by the following formula:
Notes, amendments, and revision history
Amendments
[Amdt. 179-32, 48 FR 27708, June 16, 1983; 49 FR 42736, Oct. 24, 1984; 64 FR 51920, Sept. 27, 1999, as amended at 66 FR 45390, Aug. 28, 2001; 68 FR 75763, Dec. 31, 2003; 85 FR 45030, July 24, 2020; 90 FR 26459, June 23, 2025; 90 FR 28044, July 1, 2025]
Source
Source: Amdt. 179-32, 48 FR 27708, June 16, 1983, unless otherwise noted.
Authority
Authority: 49 U.S.C. 5101-5128; 49 CFR 1.81 and 1.97.
Source
Source: 29 FR 18995, Dec. 29, 1964, unless otherwise noted. Redesignated at 32 FR 5606, Apr. 5, 1967.
Amendments
[Amdt. 179-32, 48 FR 27708, June 16, 1983; 49 FR 42736, Oct. 24, 1984; 64 FR 51920, Sept. 27, 1999, as amended at 66 FR 45390, Aug. 28, 2001; 68 FR 75763, Dec. 31, 2003; 85 FR 45030, July 24, 2020; 90 FR 26459, June 23, 2025; 90 FR 28044, July 1, 2025]