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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 #11-0046 ([Chart Industries] [Mr. Dan Bricker])

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

Interpretation Response Details

Response Publish Date:

Company Name: Chart Industries

Individual Name: Mr. Dan Bricker

Location State: IN Country: US

View the Interpretation Document

Response text:

April 18, 2011



Mr. Dan Bricker

Chart Industries

2800 Airwest Blvd.

Plainfield, In. 46168

Reference No.: 11-0046

Dear Mr. Bricker:

This responds to your letter concerning the transport of cryogenic liquids under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you ask how the definition of the term "service pressure" and the exceptions for cryogenic liquids provided in § 173.320 of the HMR apply to specification DOT-4L welded insulated cylinders used to transport medical oxygen. In your incoming letter, you state that you wish to transport medical oxygen in a 46 Liter insulated liquid oxygen (LOX) container. Your questions have been paraphrased and answered as follows:

Q1: What is the definition of the term "Service Pressure" as it applies to the specification for DOT 4L welded insulated cylinders specified in § 178.57?

A1: As specified in § 173.115, the term "service pressure," as it is used throughout the HMR, means the authorized pressure marking on the packaging. For example, for a cylinder marked "DOT 3A1800," the service pressure is 12,410 kPa (1,800 psig). The 46 Liter insulated LOX container you describe in your incoming letter cannot be considered a DOT-4L cylinder unless it has a water capacity (nominal) not over 1,000 pounds water capacity, a marked service pressure of at least 40 psig but not greater than 500 psig, and the cylinder conforms to all other specifications required in § 178.57.

Q2: Does the 46 Liter insulated liquid oxygen (LOX) container described in the incoming letter meet the exceptions provided in § 173.320?

A2: The packaging exceptions for cryogenic liquids are found in § 173.320 and allow for alternative packaging methods. In accordance with § 173.320(a), atmospheric gases and helium, cryogenic liquids, in Dewar flasks, insulated cylinders, insulated portable tanks, insulated cargo tanks, and insulated tank cars, designed and constructed so that the pressure in such packagings will not exceed 25.3 psig under ambient temperature conditions during transportation are not subject to the requirements of this subchapter when transported by motor vehicle or railcar except as specified in paragraphs (a)(1), (a)(2), and (a)(3) of § 173.320. Provided your container meets the requirements of

§ 173.320, it may be transported in the 46 Liter insulated liquid oxygen (LOX) container you describe. It should be noted, however, that the 25.3 psig referred to in § 173.320(a) is not the service pressure.

Q3: If the 46 Liter insulated liquid oxygen (LOX) container described in the incoming letter does not meet exceptions provided in § 173.320, what packaging specifications would the container need to satisfy in order to transport cryogenic liquids?

A3: The general requirements for cryogenic liquids in cylinders are found in § 173.316. If the medical oxygen packaged in insulated LOX containers does not conform to the exceptions provided in § 173.320, it must be packaged in accordance with § 173.316 and transported in a cylinder marked as a specification DOT-4L cylinder.

I hope this satisfies your inquiry. Please contact us if we can be of further assistance.


T. Glenn Foster

Chief, Regulatory Review and Reinvention Branch

Standards and Rulemaking Division

173.320, 173.115, 173.316

Regulation Sections

Section Subject
173.115 Class 2, Divisions 2.1, 2.2, and 2.3-Definitions
173.320 Cryogenic liquids; exceptions