# -6 Thickness of plates.

**Citation:** 49 CFR 179.220-6  
**Type / status:** regulation / current  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** 2026-08-18  
**Published:** Not stated

(a) The wall thickness, after forming of the inner container shell and 2:1 ellipsoidal heads must be not less than specified in § 179.221-1, or not less than that calculated by the following formula:

Where: d = Inside diameter in inches; E = 0.9 welded joint efficiency; except E = 1.0 for seamless 

## Document text

(a) The wall thickness, after forming of the inner container shell and 2:1 ellipsoidal heads must be not less than specified in § 179.221-1, or not less than that calculated by the following formula:

Where: d = Inside diameter in inches; E = 0.9 welded joint efficiency; except E = 1.0 for seamless heads; P = Minimum required bursting pressure in psig; S = Minimum tensile strength of plate material in p.s.i. as prescribed in AAR Specifications for Tank Cars, appendix M, Table M1; t = Minimum thickness of plate in inches after forming.

(b) The wall thickness after forming of the inner container heads, if flanged and dished, must be not less than specified in § 179.221-1, or not less than that calculated by the following formula:

Where: E = 0.9 welded joint efficiency; except E = 1.0 for seamless heads; L = Main inside radius to which head is dished, measured on concave side in inches; P = Minimum required bursting pressure in psig; S = Minimum tensile strength of plate material in psi as prescribed in AAR Specifications for Tank Cars, appendix M, Table M1 (IBR, see § 171.7 of this subchapter); t = Minimum thickness of plate in inches after forming.

(c) The wall thickness after forming of the cylindrical section and heads of the outer shell must be not less than seven-sixteenths of an inch.

(d) See § 179.220-9 for plate thickness requirements for inner container when divided into compartments.

[Amdt. 179-9, 36 FR 21340, Nov. 6, 1971, as amended at 66 FR 45390, Aug. 28, 2001; 68 FR 75762, Dec. 31, 2003]

## Provenance

- Official: Yes
- Source: <https://www.ecfr.gov/on/2026-08-18/title-49/section-179.220-6>
- Source ID: `ecfr`
- SHA-256: `a8d444948811ace923c5cf4e33e65bde4598956f059b6a9d0ca2c0d28762d2ce`
- Retrieved: 2026-08-20T05:46:20.606Z
- Exported: 2026-08-25T11:51:50.623Z
- Document slug: `49-cfr-179-220-6`

### Source metadata

```json
{
  "cfrTitle": 49,
  "part": "179",
  "section": "179.220-6",
  "subpart": "Subpart D—Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW, 115AW, and 117AW)",
  "corpusVersion": "2026-08-18",
  "jurisdiction": "US"
}
```