USA Banner

Official US Government Icon

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure Site Icon

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #23-0014

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

Interpretation Response Details

Response Publish Date:

Company Name: Fleener Consulting LLC

Individual Name: Mr. Arthur Fleener

Location State: IA Country: US

View the Interpretation Document

Response text:

August 21, 2023

Mr. Arthur Fleener
Fleener Consulting LLC
3741 Mathews Rd
Ames, IA  50014

Reference No. 23-0014

Dear Mr. Fleener:

This letter is in response to your February 27, 2023, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the installation of U.S. Department of Transportation (DOT) 400-series cargo tank pressure relief devices (PRDs) on Motor Carrier (MC) 300-series cargo tank motor vehicles (CTMVs). Specifically, you state that the Pipeline and Hazardous Materials Safety Administration (PHMSA) has issued conflicting guidance pertaining to the requirements for a DOT 400-series PRD when installed on an MC 300-series CMTV. You included a copy of a final rule published by PHMSA on June 18, 2018—issued under Docket No. PHMSA-2013-0225 (HM-218H)—in response to appeals of a previously published final rule. You interpret this "Correcting Amendments" rulemaking as stating that a DOT 400-series PRD can be installed on an MC 300-series tank, but it must meet the venting capacity and set pressure requirements of the original specification of the 300-series tank. You also include a PHMSA letter of interpretation (Ref. No. 17-0065) which you interpret as stating that a person may install a DOT 400-series PRD on an MC 300-series cargo tank, but the PRD would not be required to function like an MC 300-series PRD.

We have paraphrased and answered your questions as follows:

Q1. You state that your understanding of the June 18, 2018, "Correcting Amendments" rulemaking is that a modified PRD on an MC-307 CTMV is required to meet the set pressure requirements of the original specification, which is to open at not less than the cargo tank maximum allowable working pressure (MAWP) and not more than 110% of the MAWP, reseating at a pressure of no less than 90% of the MAWP. You have included preamble language from the June 18, 2018, "Correcting Amendments" rulemaking which states that "while the HMR permits DOT 400-series PRDs to be installed on MC 300-series CTMVs, the PRDs must still meet the venting capacity and set pressure requirements of the original specification, in accordance with §§ 173.33(d)(3) and 180.407(h)(2)." You ask whether your understanding is accurate.

A1. Your understanding of the June 18, 2018, "Correcting Amendments" rulemaking is not correct. The June 18, 2018, "Correcting Amendments" rulemaking did not amend § 180.407(j) or any other regulatory text related to the permitted use of modified PRDs on MC 300-series CTMVs. However, in an effort to respond to some ongoing questions around those provisions, we acknowledge that some incorrect and some imprecise preamble language was used in that rulemaking. First, the correct citations in the preamble language you included should have read, "§§ 173.33(d)(3) and 180.405(h)(3)." Second, the preamble language is imprecise when it states that modified PRDs on MC 300-series tanks must still meet the venting capacity and set pressure requirements of the original specification. To be clear, the venting capacity of the original specification must be met as stated in §§ 173.33(d)(3) and 180.405(h)(3), but nowhere in the HMR does it require the set pressure of the original specification to be met. Finally, as explained in letter of interpretation (Ref. No. 17-0065), a modified PRD installed on an MC-307 CTMV would be required to open between 120% and 132% of the MAWP and reclose at not less than 108% of the MAWP, (see § 180.407(j)(1)(ii)(B)).

Q2. You ask whether the June 18, 2018, "Correcting Amendments" rulemaking supersedes the PHMSA letter of interpretation (Ref. No. 17-0065) which states that an MC-307 PRD modified to conform to DOT-407 specifications on a 30 psig MAWP CTMV would be required to open between 36 psig (120% of MAWP) and 39.6 psig (132% of MAWP), as prescribed in §§ 180.407(j)(1)(ii)(B), 178.347-4(c), and 178.345-10(d)(1).

A2. As stated in answer A1, PHMSA acknowledges that there is incorrect and imprecise preamble language in the June 18, 2018, rulemaking. Furthermore, the referenced letter of interpretation remains accurate (Ref. No. 17-0065).

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

Sincerely,

T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division

173.33(d)(3), 178.345-10(d)(1), 178.347-4(c), 180.407(h)(2), 180.405(h)(3), 180.407(j), 180.407(j)(1)(ii)(B)

Regulation Sections

Section Subject
173.33 Hazardous materials in cargo tank motor vehicles
178.345-10 Pressure relief
178.347-4 Pressure relief
180.405 Qualification of cargo tanks
180.407 Requirements for test and inspection of specification cargo tanks