# Minimum thickness of shells and heads.

**Citation:** 49 CFR 178.272-2  
**Type / status:** regulation / historical  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** 2005-10-01  
**Published:** Not stated

(a) The approval agency may authorize a minimum thickness less than that required by § 178.270-5 of this subpart where additional protection against tank puncture provides equal integrity.

(b) The shell and head thickness of a tank must be at least:

(1) 3.18 mm (0.125 inches) for a tank with a max

## Document text

(a) The approval agency may authorize a minimum thickness less than that required by § 178.270-5 of this subpart where additional protection against tank puncture provides equal integrity.

(b) The shell and head thickness of a tank must be at least:

(1) 3.18 mm (0.125 inches) for a tank with a maximum cross-sectional dimension of 1.8 m (5.9 feet) or less; or

(2) 4 mm (0.157 inches) for a tank constructed of the reference mild steel having a maximum cross-sectional dimension exceeding 1.8 m (5.9 feet). For tanks having a maximum cross-sectional dimension exceeding 1.8 m (5.9 feet) constructed of other steels, an equivalent head and shell thickness calculated in accordance with § 178.270-5(c) of this subpart may be used, subject to an absolute minimum of 3.18 mm (0.125 inches).

(c) The following additional puncture protection systems are authorized:

(1) An overall external structural protection, such as a jacket, which is rigidly secured to the tank with a layer of cushioning material installed between the external structural protection and the tank; or

(2) A complete framework surrounding the tank including both longitudinal and transverse structural members.

[Amdt. 178-65, 46 FR 9899, Jan. 29, 1981, as amended at 66 FR 45387, Aug. 28, 2001]

## Provenance

- Official: Yes
- Source: <https://www.govinfo.gov/app/details/CFR-2005-title49-vol2/CFR-2005-title49-vol2-sec178-272-2>
- Source ID: `govinfo-cfr`
- SHA-256: `5945ad05b7b9a199c58d3c72ecea9cc06bf4aa23823725edca55b8eabed7c4f4`
- Retrieved: 2026-08-13T06:37:34.028Z
- Exported: 2026-08-23T14:42:44.917Z
- Document slug: `49-cfr-178-272-2`

### Source metadata

```json
{
  "part": "178",
  "section": "178.272-2",
  "subpart": "Subpart H—Specifications for Portable Tanks",
  "annualEdition": 2005,
  "revisedAsOf": "2005-10-01",
  "govInfoPackage": "CFR-2005-title49-vol2",
  "legalStatus": "official-annual-cfr-edition",
  "effectiveDateNote": null,
  "historicalAnchor": true,
  "historicalAnchorNote": "The section appears in an official annual CFR edition but is absent from the connected current eCFR corpus.",
  "jurisdiction": "US"
}
```