# -7 Tank heads.

**Citation:** 49 CFR 179.400-7  
**Type / status:** regulation / current  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** 2026-08-18  
**Published:** Not stated

(a) Tank heads of the inner tank and outer jacket must be flanged and dished, or ellipsoidal.

(b) Flanged and dished heads must have—

(1) A main inside dish radius not greater than the outside diameter of the straight flange;

(2) An inside knuckle radius of not less than 6 percent of the outside 

## Document text

(a) Tank heads of the inner tank and outer jacket must be flanged and dished, or ellipsoidal.

(b) Flanged and dished heads must have—

(1) A main inside dish radius not greater than the outside diameter of the straight flange;

(2) An inside knuckle radius of not less than 6 percent of the outside diameter of the straight flange; and

(3) An inside knuckle radius of at least three times the head thickness.

## Provenance

- Official: Yes
- Source: <https://www.ecfr.gov/on/2026-08-18/title-49/section-179.400-7>
- Source ID: `ecfr`
- SHA-256: `e4749f109744a7ee228ccecf78cd4732f6effa8d8edfa2babd5028f7460cd64e`
- Retrieved: 2026-08-20T05:46:20.606Z
- Exported: 2026-08-23T19:48:24.646Z
- Document slug: `49-cfr-179-400-7`

### Source metadata

```json
{
  "cfrTitle": 49,
  "part": "179",
  "section": "179.400-7",
  "subpart": "Subpart F—Specification for Cryogenic Liquid Tank Car Tanks and Seamless Steel Tanks (Classes DOT-113 and 107A)",
  "corpusVersion": "2026-08-18",
  "jurisdiction": "US"
}
```