# Praxair Engineering Fellow — Hazardous Materials Safety Interpretation

- **operation:** document
- **citation:** 14-0038
- **title:** Praxair Engineering Fellow — Hazardous Materials Safety Interpretation
- **source type:** guidance
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** guidance
- **official:** true
- **published on:** 2014-04-30
- **effective on:** Not available
- **summary:** 14-0038 response to Praxair Engineering Fellow concerning 180.207.
- **machine formats:** - **json:** https://regulus.evalyn.ai/document/phmsa-interpretation-14-0038.json
- **markdown:** https://regulus.evalyn.ai/document/phmsa-interpretation-14-0038.md
- **app url:** https://regulus.evalyn.ai/document/phmsa-interpretation-14-0038
- **source url:** https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/2014/140038.pdf
**body:**

<<<PAGE 1>>>

U.S. Department
of Transportation
Pipeline and Hazardous
Materials Safety
Administration
1200 New Jersey Avenue, SE
Washington, D.C. 20590
APR 2 8 2014
Mr. Mahendra D. Rana, P.E., ASME Life Fellow,
Praxair Engineering Fellow
Praxair, Inc.
175 East Park Drive
Tonawanda, NY 14151
Ref. No. 14-0038
Dear Mr. Rana:
This responds to your Febraury 27, 2014letter regarding the requalification testing
requirements for a seamless steel UN pressure receptacle (cylinder) under§ 180.207(d)(l)
of the Hazardous Materials Regulations (HMR; 49 CPR Parts 171-180). Specifically, you
ask if the hydrostatic volumetric expansion test is an authorized testing method for
requalifying an "H" marked seamless steel UN cylinder with a tensile strength of< 950
MPa.
The answer to your question is yes; Section 180.207(d)(l) requires that each seamless steel
UN pressure receptacle is requalified in accordance with ISO 6406: Seamless Steel Gas
Cylinders-Periodic Inspection and Testing (see§ 171.7), but that UN cylinders with a
tensile strength 2: 950 MPa must be requalified only by ultrasonic examination. ISO 6406
requires that each cylinder is submitted for either a pressure test or an ultrasonic
examination. The pressure test may be either the hydrostatic volumetric expansion or the
hydraulic proof pressure test.
ISO 11114-1: Transportable gas cylinders, Compatibility of cylinder and valve
materials with gas contents provides guidance in the selection and evaluation of
compatibility between UN seamless steel and the gas content. Specifically, ISO 11114-1
states that UN seamless steel cylinders with a tensile strength ::S 950 MPa, are compatible
with hydrogen, hydrogen mixtures and hydrogen bearing compounds including hydrides.
Section 173.301 b(f) requires that cylinders compatable with hydrogen, hydrogen mixtures,
and hydrogen bearing compounds bear an 'H' mark.
In a final rulemaking (HM-220E; 71 FR 33858, 33870; June 12, 2006) PHMSA stated that
those cylinders bearing an "H" mark may be pressure tested and those bearing no "H" mark
must be requalified by ultrasonic examination in accordance with ISO 6406 by an approved
req ualifi er.
Therefore, "H" marked seamless steel UN cylinders may be pressure tested or subjected to
an ultrasonic examination. PHMSA recognizes that as currently written §180.207(d)(l)
conflicts with ISO 11114-1 with regard to the tensile strength values and the required
requalification method. It was PHMSA's intention that those cylinders bearing an "H"

<<<PAGE 2>>>

mark may be pressure tested and those not bearing the 'H' mark must be requalified by
ultrasonic examination in accordance with ISO 6406 by an approved requalifier. We
intend to clarify the tensile strength values referenced in§ 180.207(d)(l) in a future
rulemaking. A related letter of interpretation (Reference No. 13-0137) is attached for your
reference.
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

<<<PAGE 3>>>

Praxair, Inc.
175 East Park Drive
Tonawanda, NY, 14151
Phone: 716-879-2000
2/27/14
To: Director of Standards Division
Office of Hazardous Materials Technology & Research
US Department of Transportation
Subject: Interpretation Request on Requalification UN cylinders
The present §180.207 (d) (1) on the requalification of UN pressure receptacles requires
that UN cylinders with a tensile strength greater than or equal to 950 MPa must be
requalified by ultrasonic examination in accordance with ISO 6406. UN cylinders designed and
constructed to ISO 9809-1 H mark have tensile strength less than or equal to 950 MPa.
Present wording in the above paragraph (d)(1) precludes the requalification of the H marked
cylinders by hydrostatic test with tensile strength equal to 950 MPa. We are requesting the
following interpretation.
Question: For H marked UN cylinders, can hydrostatic test be used in lieu of the specified
ultrasonic test in §180.207 (d) (1).
Answer: Yes, UN cylinders with H mark may be requlified by hydrostatic test.
Very truly yours,
Mahendra D. Rana, P.E., ASME Life Fellow,
Praxair Engineering Fellow
Praxair, Inc.
1 7 5 East Park Drive
Phone & Fax No: (716) 879-2408/2907
E-mail: Mahendra_ Rana@praxair.com
- **truncated:** false
- **body characters:** 4306