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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 #21-0035

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

Interpretation Response Details

Response Publish Date:

Company Name: Momentive Performance Materials

Individual Name: Kirsten Pink

Location State: NY Country: US

View the Interpretation Document

Response text:

June 2, 2021

Kirsten Pink
AMR Supply Chain Regulatory Leader
Momentive Performance Materials
260 Hudson River Road
Waterford, NY 12188

Reference No. 21-0035

Dear Ms. Pink:

This letter is in response to your April 5, 2021, letter and subsequent email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the pressure relief device settings on a Department of Transportation (DOT) Specification 51 portable tank to be used in the transportation of "UN1993, Flammable liquids, n.o.s., 3, PG II." Specifically, you state that it is your understanding that the requirements for the setting of pressure relief devices on DOT Specification 51 portable tanks are found in § 178.275(g)(6). You seek confirmation that the pressure relief device must be set to start to discharge at a nominal pressure of 264 psi (~18.2 bar) for a DOT Specification 51 portable tank with a test pressure of 360 psi (~24.8 bar).

Paragraph (f)(2) of § 173.32 states that a hazardous material may not be loaded in a DOT Specification 51, DOT Specification 60, an IM or UN portable tank unless the portable tank has a pressure relief device that provides total relieving capacity meeting the requirements of the HMR. The requirements for the setting of pressure relief devices for portable tanks intended for the transportation of liquid and solid hazardous materials are specified in § 178.275(g)(6)(ii). This section states that for shells with a test pressure of more than 4.5 bar, the pressure relief device must be set to start to discharge at 110% of two-thirds of the test pressure. Therefore, the start to discharge setting on a pressure relief device would be 264 psig (~18.2 bar) for a DOT Specification 51 portable tank with a test pressure of 360 psig (~24.8 bar).

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

173.32, 178.275(g)(6), 178.275(g)(6)(ii)

Regulation Sections

Section Subject
173.32 Requirements for the use of portable tanks
178.275 Specification for UN Portable Tanks intended for the transportation of liquid and solid hazardous materials