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Interpretation Response #09-0111 ([Carroll Welding Supply] [Mr. Wood Smith])

Below is the interpretation response detail and a list of regulations sections applicable to this response.

Interpretation Response Details

Response Publish Date:

Company Name: Carroll Welding Supply

Individual Name: Mr. Wood Smith

Location State: TX Country: US

View the Interpretation Document

Response text:

December 3, 2010




Mr. Wood Smith

General Manager

Carroll Welding Supply

P.O. Box 1897

Abilene, TX 79604

Reference No. 09-0111

Dear Mr. Smith:

This is in response to your letters asking for clarification of the requirements in § 180.212(b) of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you ask about the type of work that may be done to DOT 3-series cylinders and UN pressure receptacles authorized by a cylinder retester. We have paraphrased your questions and answered them in the order you provided. We apologize for the delay in responding and any difficulty this may have caused.

Q1. Under § 180.212(b)(1), may a cylinder requalifier with a valid requalification identification number (RIN) repair a foot ring on a DOT 3-series cylinder by removing it and welding a new foot ring in its place provided the repair does not affect the pressure part of the cylinder?

A1. No. Section § 180.212(b)(1) authorizes the removal and replacement of a neck ring or foot ring that does not affect a pressure part of a DOT 3A, 3AA, 3B or UN cylinder when the repair is performed by an authorized repair facility with a valid "K" number or a cylinder manufacturer of these types of cylinders. The repair must be performed under the supervision of an inspector and must be performed in conformance with the original cylinder specification.

Q2. May a cylinder owner, requalifier, or repair facility clean the internal threads of a DOT 3-series cylinder in any gas service using a thread tap of suitable size for the cylinder? Does insertion of the thread tap constitute a re-threading operation under 180.212(b)(2)?

A2. Any procedure that causes a non-functioning thread section to function properly is considered a "rethreading" operation for purposes of the HMR. When such operations are conducted by a manufacturer of DOT 3 series or UN cylinders, the approval provisions of 49 CFR Part 107, Subpart H, do not apply. If the re-threading is conducted by a person other than a manufacturer, the facility must hold an approval issued under the provisions of 49 CFR 107.805. Note that no DOT or UN specification cylinder may be re-threaded more than once without the approval of the Associate Administrator for Hazardous Materials Safety (Associate Administrator). Cleaning the internal neck threads of a cylinder using a tool such as a chaser, brush, or other similar tool is not consider a re-thread or repair on a DOT 3-series cylinder and may be performed by a cylinder requalifier.

Q3. What does the phrase "repairs not requiring approval" mean?

A3. As used in § 180.212, the phrase "repairs not requiring prior approval" refers to the two operations (removal and replacement of neck rings or foot rings, and rethreading in the manner prescribed) described under that section. The phrase means that the operations described may be performed without first obtaining an approval from the Associate Administrator under 49 CFR Part 107, Subpart H.

I hope this satisfies your request.


T. Glenn Foster

Chief, Regulatory Review and Reinvention

Standards and Rulemaking Division


Regulation Sections

Section Subject
180.212 Repair of seamless DOT 3-series specification cylinders and seamless UN pressure receptacles