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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 #18-0036R

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

Interpretation Response Details

Response Publish Date:

Company Name: Association of American Railroads

Individual Name: Kenneth Dorsey

Location State: DC Country: US

View the Interpretation Document

Response text:

May 09, 2019

Kenneth B. Dorsey
Association of American Railroads
425 Third Street, SW
Washington, DC 20024

Reference No. 18-0036R

Dear Mr. Dorsey:

The Pipeline and Hazardous Materials Safety Administration is clarifying this previously issued letter of interpretation based on further review. In your March 13, 2018, letter, you had requested clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to specifications for DOT-111 and DOT-117 series tank cars. While PHMSA's original response is accurate, it did not fully address all of your concerns. Specifically, we are expanding on our answer to Question 2 to more comprehensively address DOT-111 tank cars retrofitted to a DOT-117R specification.

We have paraphrased and answered your questions as follows:

Q1. You ask whether a DOT-111 tank car manufactured after October 1, 2015, is eligible to be retrofitted to DOT-117R or DOT-117P specification.

A1. The answer is no. In accordance with § 174.310(a)(4), if used to transport flammable liquids, only DOT-111 tank cars manufactured before October 1, 2015 are eligible to be retrofit to the DOT-117R specification.

Q2. Certain jacketed DOT-111 tank cars are equipped with fiberglass insulation, which is not an approved thermal protection system, in accordance with § 179.18(c). You ask whether these tank cars being retrofitted to the DOT-117 specification require documentation of a thermal analysis to show that they are capable of achieving the performance standard in § 179.18(a).

A2. When converting jacketed DOT-111 tank cars equipped with a thermal protection system not on the list of systems that do not require verification (see § 179.18(c)), each tank car owner must ensure a thermal analysis has been conducted, verified and documented (see § 179.18(b)) that demonstrates that the thermal protection system for the tank car(s) being converted meets the performance standard in § 179.18(a). Procedures for completing the thermal analysis are outlined in Part 179, Appendix B. To meet the requirements for the DOT-117P specification tank car, the design must receive additional approval from Associate Administrator for Railroad Safety/Chief Safety Officer, Federal Railroad Administration (FRA). Jacketed DOT-111 tank cars that are retrofitted to the DOT-117R specification do not require additional approval from the FRA, provided the requirements in § 179.18(a) and (b) are met.

Q3. You ask if the minimum plate thickness requirements for DOT-117R specification can be based on the minimum plate thickness requirement at the time of original construction.

A3. The answer is yes. In accordance with § 179.202-13(c), the minimum plate thickness for all tank cars manufactured to the DOT-117R is 7/16 of an inch. However, DOT-111 tank cars manufactured to the Association of American Railroads CPC-1232 standard have a minimum plate thickness of 1/2 an inch. Additionally, when calculating minimum allowable tank shell thickness in accordance with § 180.509(f), the original plate thickness at time of construction must be used for these calculations.

I hope this information is helpful. Please contact us if we can be of further assistance.


Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division

174.310(a)(4), 179.18(c), 179, 179.18(a), 179.18(b), 179.202-13(c), 180.509(f)

Regulation Sections

Section Subject
179.18 Thermal protection systems
179.202-13 Retrofit standard requirements (DOT-117R)
180.509 Requirements for inspection and test of specification tank cars