49 CFR § 179.200-21 - Closures for openings.

---
identifier: "/us/cfr/t49/s179.200-21"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "49 CFR § 179.200-21 - Closures for openings."
title_number: 49
title_name: "Transportation"
section_number: "179.200-21"
section_name: "Closures for openings."
chapter_name: "PIPELINE AND HAZARDOUS MATERIALS SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION"
subchapter_number: "C"
subchapter_name: "HAZARDOUS MATERIALS REGULATIONS"
part_number: "179"
part_name: "SPECIFICATIONS FOR TANK CARS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "49 U.S.C. 5101-5128; 49 CFR 1.81 and 1.97."
regulatory_source: "29 FR 18995, Dec. 29, 1964, unless otherwise noted. Redesignated at 32 FR 5606, Apr. 5, 1967."
cfr_part: "179"
---


# 179.200-21 Closures for openings.

(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]