# -7 Tank heads.

- **operation:** document
- **citation:** 49 CFR 179.400-7
- **title:** -7 Tank heads.
- **source type:** regulation
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** current
- **official:** true
- **published on:** Not available
- **effective on:** 2026-08-18
- **summary:** (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 
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- **markdown:** https://regulus.evalyn.ai/document/49-cfr-179-400-7.md
- **app url:** https://regulus.evalyn.ai/document/49-cfr-179-400-7
- **source url:** https://www.ecfr.gov/on/2026-08-18/title-49/section-179.400-7
**body:**

(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.
- **truncated:** false
- **body characters:** 410