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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 #10-0073 ([Eastman Chemical Company Texas Operations] [Ms. Marilyn Williams])

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

Interpretation Response Details

Response Publish Date:

Company Name: Eastman Chemical Company Texas Operations

Individual Name: Ms. Marilyn Williams

Location State: TX Country: US

View the Interpretation Document

Response text:

October 20, 2011



Ms. Marilyn Williams

Logistics Representative

Eastman Chemical Company

Texas Operations

P.O. Box 7444

Longview, Texas 75607-7444

Ref. No. 10-0073

Dear Ms. Williams:

This responds to your letter requesting clarification of the applicability of certain regulatory requirements under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) to a tank car that previously contained "UN1038, Ethylene, refrigerated liquid," a cryogenic, Division 2.1 (flammable gas) material. You ask whether the annular space absolute pressure requirement (< 75 microns of mercury) specified in § 173.319(b)(2) of the HMR applies to a tank car containing the residue of ethylene no longer in cryogenic form that is depressurized to 10 psi or less and purged with nitrogen. Additionally, you ask whether movement approval from the Federal Railroad Administration (FRA) under § 174.50 is necessary to offer such a purged, residue tank car for transportation if the absolute pressure does exceed 75 microns of mercury in the annular space when being offered for movement to a repair facility to correct such a deficiency. We apologize for the delay in responding and any inconvenience it may have caused.

As specified in § 173.319(b)(2), when a tank car containing a flammable cryogenic liquid is offered for transportation, the absolute pressure in the annular space must be less than 75 microns of mercury. A DOT 113 specification tank car that no longer contains flammable cryogenic liquid is not subject to this requirement because its monitoring does not provide an accurate indication of potential insulation problems. Because the residue no longer poses a risk in transportation as a flammable cryogenic liquid, the tank cars are not subject to the annular space absolute pressure requirement in § 173.319(b)(2). However, your residue may still meet the definition of a flammable gas and, therefore, be subject to other regulations. In addition, because the nonconforming tank cars are being used to transport a hazardous material residue, they are subject to movement approval by the FRA under § 174.50 when offered for transportation to a repair facility.

I trust 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

173.319, 174.50

Regulation Sections

Section Subject
173.319 Cryogenic liquids in tank cars