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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 #16-0001R

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

Interpretation Response Details

Response Publish Date:

Company Name: Patriot Tank Lines Inc.

Individual Name: Mark Mietz

Location State: NY Country: US

View the Interpretation Document

Response text:

Mark Mietz
Patriot Tank Lines Inc.
2737 Erie Drive
Weedsport, NY  13166

Reference No. 16-0001R

Dear Mr. Mietz:

The Pipeline and Hazardous Materials Safety Administration is clarifying this previously issued letter of interpretation based on further review.  In your December 22, 2015 email, you had requested clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to marking inlets and outlets on Department of Transportation (DOT) Specification MC331 cargo tank motor vehicles in accordance with § 178.337-9(c).  Specifically, you asked whether the marking required must be at the furthest point from the tank (i.e., the piping) or on the cargo tank (wall).  You also asked whether there is a size requirement for the marking and whether it needs to be stamped or embossed.

In accordance with § 178.337-9(c), each cargo tank inlet and outlet, with the exception of gauging devices, thermometer wells, and pressure relief valves, must be marked “liquid” or “vapor” to designate whether it communicates with liquid or vapor when the cargo tank is filled to the maximum filling density.  Provided the marking is readily visible, legible, durable to withstand transport conditions, and clearly associated with the corresponding inlet or outlet, it would satisfy the requirements of the HMR. 

In our original response of June 3, 2016, we stated that the required marking(s) must be on the inlet/outlet equipment itself and in close proximity to its respective make/break connection point, rather than on the cargo tank wall.  We have since reconsidered this position based on a better understanding of industry practice and ability to mark using stenciling or stickers that will not impact the integrity or certification of the cargo tank.  Thus, the marking(s) requirement may be satisfied using various locations and methods including marking on the tank shell. 

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


Shane Kelley
Standards and Rulemaking Division

Regulation Sections

Section Subject
178.337-9 Pressure relief devices, piping, valves, hoses, and fittings