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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 #14-0175 ([Linde] [Mr. John P. Smith PE])

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

Interpretation Response Details

Response Publish Date:

Company Name: Linde

Individual Name: Mr. John P. Smith PE

Location State: NJ Country: US

View the Interpretation Document

Response text:

March 13, 2015

Mr. John P. Smith, PE
Senior Transportation Engineer
575 Mountain Ave.
Murray Hill, NJ 07974

Ref. No. 14-0175

Dear Mr. Smith:

This letter responds to your September 19, 2014 email regarding required use of DOT specification rail tank cars under in the Hazardous Materials Regulations (HMR; 49 CFR parts 171-180). In your letter, you indicate that your company has historically used a DOT-105S500W tank car (foam insulated with a steel jacket) denoted with an "S" delimiter in lieu of the "A" to indicate compliance with the requirement for tank head puncture resistance for the transport of carbon dioxide (UN2187, Carbon dioxide, refrigerated liquid). Recently, you have been made aware that a car type DOT-105J500W tank car is now required with the "J" delimiter denoting thermal protection when transporting this material based on § 173.31(b)(4). Specifically, you request clarification of the correct tank car authorized for transportation of "UN2187, Carbon dioxide, refrigerated liquid."

Your tank cars have a thermal protection system that includes a steel jacket, thus, generally, the specification marking must include the "J" delimiter. However, if insulation on the cars in question does not meet the thermal protection requirements, then your tank cars cannot be stenciled with the "J" delimiter indicating thermal protection with a metal jacket. For that case, you will need a special permit to use an "S" delimiter stenciled car in Class 2 service. If the insulation on the respective tank cars does meet the thermal protection requirements, then a Form R-1 amending the certificates of construction must be submitted to the Association of American Railroads, and the stenciling on the cars needs to be changed to reflect the "J" delimiter as required.

A DOT-105 tank car is authorized under § 173.314 for transportation of "UN2187, Carbon dioxide, refrigerated liquid." DOT-105 tank cars transporting a Class 2 material must have a thermal protection or insulation system (see § 173.31(b)(4)) that meets the thermal protection system requirements in § 179.18. The "J" delimiter means the tank car is equipped with a thermal protection system covered by a (metal) jacket and is equipped with a tank head puncture-resistance system. Thus, the requirement to mark with a "J" in lieu of "A" or "S" (see § 179.22(c)). Further, in a final rule published June 26, 1996 entitled "Crashworthiness Protection Requirements for Tank Cars; Detection and Repair of Cracks, Pits, Corrosion, Lining Flaws, Thermal Protection Flaws and Other Defects of Tank Car Tanks; Corrections and Response to Petitions for Reconsideration" (HM-189M; 61 FR 33252), PHMSA revised § 173.31(b)(4)(i) to clarify that a tank car having a thermal protection system (conforming to § 179.18) and a tank car having an insulation system that has a heat flux of no more than 0.613 kilojoules per hour, per square meter, per degree Celsius temperature differential, are considered to meet the thermal protection system requirement. For example, a tank car currently marked "J" or "T," a tank car currently marked "A" but having a thermal protection material applied (e.g., 2-inches of ceramic fiber and 2-inches of glass fiber found on chlorine tank cars), and a tank car that has superior thermal resistance, such as a tank car used for carbon dioxide (refrigerated liquid), are considered to conform to the thermal protection standard.

I trust this information is helpful. If you have further questions, please do not hesitate to contact this office.


Dirk Der Kinderen
Acting Chief, Standard Development
Standards and Rulemaking Division

173.31(b)(4), 173.314, 179.22(c), 173.31(b)(4)(i), 179.18

Regulation Sections

Section Subject
173.31 Use of tank cars
173.314 Compressed gases in tank cars and multi-unit tank cars
179.18 Thermal protection systems
179.22 Marking