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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 #21-0076

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

Interpretation Response Details

Response Publish Date:

Company Name: American Cylinder and Safety

Individual Name: Myles L. TenBroeck

Location State: TX Country: US

View the Interpretation Document

Response text:

November 18, 2021

Mr. Myles L. TenBroeck
American Cylinder and Safety
P.O. Box 126 
Iowa Park, TX  76367

Reference No. 21-0076

Dear Mr. TenBroeck:

This letter is in response to your July 16, 2021, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to requalification markings for Department of Transportation (DOT) Specification 3A, 3AA, and 3AL cylinders. In your email, you state that “Table 1 to paragraph (a) - Requalification of Cylinders” in § 180.209 references only the use of volumetric expansion for requalification and associated test pressures for DOT Specification 3A, 3AA, and 3AL cylinders. You also state that the use of ultrasonic examination for requalification is referenced in § 180.213(f)(8) only in regard to requalification markings.

We have paraphrased and answered your questions as follows:

Q1. You ask whether the HMR allow for the use of ultrasonic examination as a method to requalify 3A, 3AA, and 3AL cylinders in lieu of the volumetric expansion method.

A1. The answer is no.  Currently, the use of an ultrasonic examination is not authorized in accordance with § 180.205 and would a require a special permit. Section 180.213(f) provides instructions on how to apply cylinder requalification markings for all test methods, including those authorized by a special permit.

Q2. You ask whether a cylinder requalified with the use of both ultrasonic examination and eddy current examination should be marked for both test methods.

A2. As stated in A1, the use of ultrasonic examination for the purposes of cylinder requalification requires a special permit. While the HMR do not specifically address how to mark cylinders that have undergone requalification using multiple test methods, it is the opinion of this Office that the cylinder should be marked for each requalification test method that achieved acceptable results. The marking of any cylinders requalified according to a special permit should be done in accordance with the marking provisions of that special permit.

I hope this information is helpful. Please contact us if we can be of further assistance.


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

180.205, 180.209, 180.213(f), 180.213(f)(8)

Regulation Sections

Section Subject
180.205 General requirements for requalification of specification cylinders
180.209 Requirements for requalification of specification cylinders
180.213 Requalification markings