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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #15-0011 ([CTC Certified Training Company] [Mr. Darrell K. Garton])

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

Interpretation Response Details

Response Publish Date:

Company Name: CTC Certified Training Company

Individual Name: Mr. Darrell K. Garton

Location State: CO Country: US

View the Interpretation Document

Response text:

April 23, 2015

Mr. Darrell K. Garton
CTC Certified Training Company
4082 Pioneer Road
Montrose, CO 81403

Reference No. 15-0011

Dear Mr. Garton:

This is in response to your January 15, 2015 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the maintenance and requalification of hermetically sealed fire extinguishers manufactured to meet the requirements of a Department of Transportation (DOT) 4DS specification cylinder and several Special Permits issued by the Pipeline and Hazardous Materials Safety Administration (PHMSA) (e.g., DOT-SP 7026, 7945, 8439, 8495, 10867). We have paraphrased your questions and answered them in the order you provided.

Q1. In the August 25, 2014 e-mail response, PHMSA’s Field Services Support Division stated that the "K" approval of DOT 4DS cylinder requalifiers prescribed in §§ 107.805 and 180.211 is required if a rupture disc in a pressure relief device (PRD) is replaced on a cylinder rebuild without heat treatment. You ask if the person rebuilding the cylinder is required to have a "K" approval before he or she can replace a rupture disc on the hermetically sealed DOT 4DS fire extinguishers you described?

A1. The answer is no. In the scenario you described, the PRD is removed from the DOT 4DS to perform a cylinder requalification. If the cylinder passes the requalification, a new PRD is placed on the cylinder by welding it to the "boss." Because the boss is fusion welded to the cylinder and the PRD is welded to the boss, the PRD does not come in direct contact with a pressure part of the cylinder and, therefore, its installation is not a "rebuild" or "repair" as these terms are defined under § 180.203 of the HMR. Persons who replace a rupture disc in a PRD on a DOT 4DS cylinder must be properly trained to perform this task in conformance with 49 CFR Part 172, Subpart H (Training).

Q2. If the procedure to replace the rupture disc on a DOT 4DS cylinder does fall under the rebuilding requirements specified in § 180.211 and a "K" approval is required, please clarify how the approval holder will not be in violation of the HMR when performing this action since it is impossible to comply simultaneously with the requirements prescribed in §§ 180.211(d)(2)(ii) (visual inspection after removal of a non-pressure component) and 180.211(d)(2)(iv) (welding and inspecting a rebuilt cylinder).

A2. As stated earlier, the procedure to replace a PRD that contains a rupture disc on a DOT 4DS cylinder is neither a "rebuild" or "repair" under the HMR criteria, and is not subject to the "K" approval requirements. As a result, the requalifier is required to perform only the visual inspection prescribed in § 180.211(d)(2)(ii).

Thank you for bringing this matter to our attention. We may consider clarifying this requirement in a future rulemaking.

I hope this satisfies your request.


T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

107.805, 180.211,180.203, 180.211, 180.211(d)(2)(ii)

Regulation Sections

Section Subject
107.805 Approval of cylinder and pressure receptacle requalifiers
180.203 Definitions
180.211 Repair, rebuilding and reheat treatment of DOT-4 series specification cylinders