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Interpretation Response #18-0118

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

Interpretation Response Details

Response Publish Date:

Company Name: HazMat Resources, Inc.

Individual Name: Daniel Shelton

Location State: TN Country: US

View the Interpretation Document

Response text:

December 3, 2019

Daniel Shelton
HazMat Resources, Inc.
141 Wendover Drive
Kingsport, TN  37660

Reference No. 18-0118

Dear Mr. Shelton:

This letter is in response to your August 27, 2018, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the pressure relief device (PRD) requirements for MC 300 series cargo tank motor vehicles (CTMV).

We have paraphrased and answered your questions as follows:

Q1. You ask what the terms "modify" and "replacement" mean as they pertain to §§ 173.33(d) and 180.405(h).

A1. The terms "modify" and "replacement" are used in the same context regarding the PRD requirements for CTMVs—i.e., "modify" meaning change from a current specification to an authorized alternative specification and "replacement" meaning substituting the old specification PRD with the authorized alternative specification PRD. For example, you may modify an MC 307 PRD by replacing it with a DOT 407 PRD. Furthermore, in accordance with § 180.405(h)(1), until August 31, 1998, the owner of a cargo tank could replace a reclosing PRD with a device which complied with the specification requirements for PRDs in effect at the time the cargo tank specification became superseded (e.g., a new or refurbished MC 300 series PRD). After that date, if the PRD on a MC 300 series CTMV is no longer properly functioning, it must be replaced with a PRD that meets the requirements of § 178.345-10.

Q2. You ask whether the original specification requirements no longer apply to MC 306, 307 and 312 CTMVs currently in-service given that new CTMVs cannot be constructed in accordance with those specifications.

A2. The original specification requirements still apply to in-service MC 306, MC 307 and MC 312 CTMVs. However, a newly constructed CTMV or its components, such as PRDs, are not authorized to be constructed in accordance with the MC 300 series specifications. A newly manufactured PRD must be constructed in accordance with § 178.345-10.

With respect to your comments about the preamble text of final rule, "Hazardous Materials: Miscellaneous Amendments; Response to Appeals; Corrections" (HM-218H), we recognize that this language has caused some confusion. We hope that the responses in this letter can provide further clarity. Moreover, we affirm that the response in Interpretation Letter Ref. No. 16-0183 is accurate.

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

173.33(d), 180.405(h), 180.405(h)(1), 178.345-10

Regulation Sections

Section Subject
173.33 Hazardous materials in cargo tank motor vehicles
178.345-10 Pressure relief
180.405 Qualification of cargo tanks