# -21 Closures for openings.

**Citation:** 49 CFR 179.200-21  
**Type / status:** regulation / current  
**Agency:** Pipeline and Hazardous Materials Safety Administration  
**Effective:** 2026-08-18  
**Published:** Not stated

(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

## Document text

(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]

## Provenance

- Official: Yes
- Source: <https://www.ecfr.gov/on/2026-08-18/title-49/section-179.200-21>
- Source ID: `ecfr`
- SHA-256: `9fce2479a50fd4778cfae65d18cd1733e167be1943ebc3a725a2541eef7c3986`
- Retrieved: 2026-08-20T05:46:20.606Z
- Exported: 2026-08-25T12:52:38.784Z
- Document slug: `49-cfr-179-200-21`

### Source metadata

```json
{
  "cfrTitle": 49,
  "part": "179",
  "section": "179.200-21",
  "subpart": "Subpart D—Specifications for Non-Pressure Tank Car Tanks (Classes DOT-111AW, 115AW, and 117AW)",
  "corpusVersion": "2026-08-18",
  "jurisdiction": "US"
}
```