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 #16-0191

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

Interpretation Response Details

Response Publish Date:

Company Name: Wisconsin State Patrol

Individual Name: Karl Kronau

Location State: WI Country: US

View the Interpretation Document

Response text:

Mr. Karl Kronau
Wisconsin State Patrol
911 W. North Street
Deforest, WI 53532

Reference No. 16-0191

Dear Mr. Kronau:

This letter is in response to your November 17, 2016, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to required markings on the inlet and outlet equipment on MC331 cargo tank motor vehicles. Specifically, you reference a letter of interpretation previously-issued under Reference No. 16-0001.

We have paraphrased and answered your questions as follows:

Q1. You ask whether the marking requirements in § 178.337-9(c), which require each cargo tank inlet and outlet to be marked "liquid" or "vapor," are satisfied if the markings are placed on the accident damage protection frame.

A1. The answer is no.  Each cargo tank inlet and outlet must be marked to indicate whether it communicates with liquid or vapor when the cargo tank is filled to the maximum permitted filling density. Marking the accident damage protection device required by § 178.337-10 does not satisfy the requirements of § 178.337-9(c).

Q2. You ask whether communicating "liquid" or "vapor" markings using durable tags attached by a wire that hangs loosely but is secured to the piping, outlet, or valve is an acceptable method of marking the cargo tank inlet and outlet in accordance with § 178.337-9(c).

A2. The answer is yes. The marking does not necessarily need to be rigidly attached to the piping, outlet, or valve handle.  Attaching the marking with wire is sufficient provided that it is readily visible and durable such that it withstands the wear and tear of transport conditions.

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


Dirk Der Kinderen
Chief, Standards Development
Standards and Rulemaking Division

Regulation Sections

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