# -21 Closures for openings.

- **operation:** document
- **citation:** 49 CFR 179.200-21
- **title:** -21 Closures for openings.
- **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) All plugs shall be solid, with NPT threads, and shall be of a length which will screw at least 6 threads inside the face of fitting or tank. Plugs, when inserted from the outside of tank heads, shall have the letter “S” at least 3/8 inch in size stamped with steel stamp or cast on the outside su
- **machine formats:** - **json:** https://regulus.evalyn.ai/document/49-cfr-179-200-21.json
- **markdown:** https://regulus.evalyn.ai/document/49-cfr-179-200-21.md
- **app url:** https://regulus.evalyn.ai/document/49-cfr-179-200-21
- **source url:** https://www.ecfr.gov/on/2026-08-18/title-49/section-179.200-21
**body:**

(a) All plugs shall be solid, with NPT threads, and shall be of a length which will screw at least 6 threads inside the face of fitting or tank. Plugs, when inserted from the outside of tank heads, shall have the letter “S” at least 3/8 inch in size stamped with steel stamp or cast on the outside surface to indicate the plug is solid.

(b) [Reserved]
- **truncated:** false
- **body characters:** 352