Interpretation Response #11-0237

Interpretation Response Details

February 13, 2012

Mr. Steve Therneau
Chart, Inc.
1300 Airport Drive
Ball Ground, GA 30107

Reference No.: 11-0237

Dear Mr. Therneau:

This responds to your letter requesting clarification of Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the repair and rebuild of Department of Transportation (DOT) 4 series specification cylinders. Specifically, you seek clarification of the definitions of "repair" and "rebuild" with regard to DOT specification cylinders and the associated requirements for the repair and rebuild of DOT specification cylinders.

In your letter, you state it is your understanding that if the inner vessel of a DOT-4 series cylinder has not been compromised, there is no requirement to test the cylinder in accordance with the specifications under which the cylinder was originally manufactured as specified in § 180.211(c)(2)(i).

Your understanding with regard to cylinder repair is not correct. The term "repair" is defined in § 180.203 as a procedure for correction of a rejected cylinder that may involve welding. A repair is not limited to the correction of a rejected cylinder that has had only its" inner vessel compromised. Therefore, DOT-4 series cylinders requiring repair, as defined in § 180.203, must do so in accordance with § 180.211. In addition, DOT 4L cylinders must meet additional requirements for repair specified in § 180.211(c) including being pressure-tested in accordance with the specifications under which the cylinder was originally manufactured. DOT 4L cylinders which undergo procedures that are not defined as a repair in § 180.203 are not subject to the requirements of § 180.211(c) including the requirement to be pressure-tested in accordance with the specifications under which the cylinder was originally manufactured.

Furthermore, you also state it is your understanding that if the inner vessel of a DOT-4 series cylinder has been compromised, it constitutes a rebuild and must be subjected to the requirements specified in § 180.211(d), and a proof pressure test, as specified in § 180.211(e)(3).

Your understanding with regard to cylinder rebuild is partially correct. The term "rebuild" is defined in § 180.203 as the replacement of a pressure part (e.g. a wall, head, or pressure fitting) by welding. While a "rebuild" would be required when the inner vessel of a DOT-4 series cylinder is compromised, it is not the only scenario that would constitute a "rebuild." DOT-4 series cylinders requiring rebuild, as defined in § 180.203, must do so in accordance with § 180.211. In addition, DOT 4L cylinders must meet additional requirements for repair specified in § 180.211(e) including proof pressure testing each inner containment vessel at 2 times its service pressure. DOT 4L cylinders which undergo procedures that are not defined as a rebuild in § 180.203 are not subject to the requirements of § 180.203(e).

If a DOT-4 series cylinder needs repair or rebuild as defined in § 180.203 and that cylinder is designed so that it is not possible to safely pressure test the cylinder in accordance with the specification which the cylinder was originally manufactured, you may request a special permit to except the cylinder from the requirement to be subjected to the pressure tests specified in § 180.211(c) and (e). Your application should be directed to the Approvals and Permits Division and should include specific and detailed information concerning the rationale for excepting the cylinder from the pressure test requirements. The procedures for applying for a special permit are in 49 CFR Part 107, Subpart B. You may also obtain this information at our website at http://www.phmsa.dot.gov/hazmat/regs/sp-a.

We appreciate your bringing this issue to our attention. PHMSA will attempt to improve the clarity of this issue in a future rulemaking.

Sincerely,

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

180.211, 180.203

Regulation Sections