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Interpretation Response #21-0060

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

Interpretation Response Details

Response Publish Date: 09-28-2021
Company Name: Massachusetts State Police    Individual Name: Scott Maguire
Location state: MA    Country: US

View the Interpretation Document

Response text:

September 28, 2021

Trooper Scott Maguire
Massachusetts State Police
906 Elm Street
Concord, MA  01742

Reference No. 21-0060

Dear Mr. Maguire:

This letter is in response to your May 25, 2021, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to portable tanks and cargo tanks.  We have paraphrased and answered your questions as follows:

Q1. You ask whether it is permissible to weld a specification Department of Transportation (DOT) 51 portable tank to a chassis and convert it to a cargo tank motor vehicle (CTMV) for the transportation of liquefied petroleum gas (LPG).

A1. The answer is no.  The definition of a "cargo tank" as specified in § 171.8 of the HMR does not authorize a bulk packaging that is fabricated to the specification of a portable tank. Additionally, the HMR defines a CTMV as a "motor vehicle with one or more cargo tanks permanently attached to or forming an integral part of the motor vehicle." Therefore, a DOT 51 portable tank which has been permanently attached to a motor vehicle would not constitute a CTMV as the tank is not an integral part of the motor vehicle.

Q2. You ask whether a specification DOT 51 portable tank retains its specification after being permanently attached to a vehicle.

A2. The answer is no. The portable tank as described in your inquiry was originally fabricated as a specification DOT 51 portable tank. However, once the specification DOT 51 portable tank was permanently attached to the motor vehicle, it no longer meets the definition of a "portable tank" as defined in § 171.8. Therefore, the specification DOT 51 portable tank loses its specification because it can no longer be defined as a "portable tank." See Answer A1.

Q3. You ask whether § 173.32(a)(3) applies to both specification and non-specification portable tanks.

A3. The answer is yes. The use of portable tank requirements in § 173.32(a)(3) can apply to both specification and non-specification portable tanks.

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


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

171.8, 173.32(a)(3)

Regulation Sections

Section Subject
§ 173.32 Requirements for the use of portable tanks