USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

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

Interpretation Response #13-0137 ([Western Sales and Testing, Inc.] [Mr. Mark Griffin])

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

Interpretation Response Details

Response Publish Date:

Company Name: Western Sales and Testing, Inc.

Individual Name: Mr. Mark Griffin

Location State: TX Country: US

View the Interpretation Document

Response text:

December 13, 2013

Mr. Mark Griffin
Western Sales and Testing, Inc.
114 E. 46th, P.O. Box 2446
Amarillo, TX 79105

Ref. No. 13-0137

Dear Mr. Griffin:

This responds to your June 24, 2013 email regarding the requalification requirements for a seamless steel UN pressure receptacle (cylinder) under § 180.207(d)(1) of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180).  Specifically, you ask whether use of the water jacket volumetric expansion test (i.e., a hydraulic pressure test) is authorized for a seamless steel UN cylinder with a tensile strength = 950 MPa.  

Your interpretation of § 180.207(d)(1) is that ultrasonic examination using ISO standard 6406 is required for a seamless steel UN cylinder with a tensile strength = 950 MPa.  However, you question why the HMR requires this ultrasonic examination and does not authorize the hydraulic pressure test.  You note that the UN Recommendations on the Transport of Dangerous Goods (Model Regulations) allow for use of an acoustic emission or an ultrasound test method instead of a hydraulic pressure test upon approval by the competent authority (re: 6.2.1.5 Note 2).

Your understanding is correct.  As currently required by the HMR under § 180.207(d)(1), a seamless steel UN cylinder with a tensile strength = 950 MPa must be requalified using ultrasonic examination in accordance with ISO 6406 (2005).  Note that the reference citation in the UN Model Regulations for periodic inspection and testing of a seamless steel gas cylinder authorizing the replacement of the hydraulic pressure test with ultrasonic examination in accordance with ISO 6406 has been revised (see 6.2.1.6.1 Note 3).  It still does not include a criterion for required use of ultrasonic examination.

Regarding requirements under the HMR, in a rulemaking entitled “Hazardous Materials: Requirements for UN Cylinders” (HM-220E) we originally proposed in new § 180.207(d)(1) that UN cylinders made of high strength steel with tensile strength < 950 MPa must be requalified in accordance with ISO 6406 and those with tensile strength = 950 MPa must be requalified as specified in § 180.209 or in accordance with procedures approved by the Associate Administrator.  For example, as was proposed, UN cylinders constructed to ISO 9809–1 or ISO 9809–2 with a tensile strength = 950 MPa could be examined by a nondestructive method that is approved by the Associate Administrator (see HM-220E; 70 FR 11774, 11799; March 9, 2005).  

In response to this proposal, industry representatives submitted comments requesting PHMSA to require all seamless steel UN cylinders to be requalified in accordance with ISO 6406.  The representatives asserted that requalifiers would not be able to determine the 950 MPa limitation because the tensile strength is not required to be marked on a cylinder.  We noted that UN seamless steel cylinders with a tensile strength < 950 MPa will bear an “H” mark to indicate compatibility of the steel with corrosive or embrittling gases.  Thus, we stated that those cylinders bearing an “H” mark may be tested hydrostaticly and those bearing no “H” mark must be requalified by ultrasonic examination in accordance with ISO 6406 by an approved requalifier.  However, the regulatory text adopted in the final rule did not fully reflect this preamble discussion.  PHMSA adopted language that required requalification in accordance with ISO 6406 or procedures approved by the Associate Administrator (see HM-220E; 71 FR 33870, 33895; June 12, 2006).  

Subsequently, in a final rule entitled “Minor Editorial Corrections and Clarifications” (HM-189Z), we revised § 180.207(d)(1) to reflect our intent in the preamble discussion of final rule HM-220E.  Specifically, we adopted the requirement that UN cylinders with a tensile strength = 950 MPa must be requalified using ultrasonic examination in accordance with ISO 6406 (HM-189Z; 71 FR 54397; September 14, 2006).

I hope this information is helpful.  If you have further questions, please contact this office.

Sincerely,

Robert Benedict
Chief, Standards Development Branch
Standards and Rulemaking Division

180.207, 180.209

Regulation Sections

Section Subject
180.207 Requirements for requalification of UN pressure receptacles
180.209 Requirements for requalification of specification cylinders