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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 #18-0121

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

Interpretation Response Details

Response Publish Date:

Company Name: Railroad Commission of Texas

Individual Name: Adam Rodriguez

Location State: TX Country: US

View the Interpretation Document

Response text:

February 5, 2019

Adam Rodriguez
Railroad Commission of Texas
AFS Department
622 S. Oakes St. #J
San Angelo, TX 76903

Reference No. 18-0121

Dear Mr. Rodriguez:

This letter is in response to your September 4, 2018, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to periodic testing and inspection of MC 331 cargo tanks. Specifically, you ask two questions in reference to the § 180.407(c) table for internal visual inspection and pressure test intervals.

We have paraphrased and answered your questions as follows:

Q1. You ask whether MC 331 cargo tanks that have less than 3,500 gallons water capacity, are constructed of NQT SA-612 steel (or other approved materials), and are used to transport propane and other liquefied petroleum gases (LPGs) such as butane, isobutane, propylene and butylenes are eligible for the 10-year interval for visual inspection. 

A1. The answer is no. The exception from the baseline 5-year requalification is limited to cargo tanks in "dedicated propane service." The phrase "dedicated propane service" means that the cargo tank is used to transport propane gas exclusively; the term does not extend to other LPGs.

Q2. You ask whether MC 331 cargo tanks that meet the capacity and material of construction criteria but are used to transport LPGs other than propane must "go back" to the 5-year interval listed in the table in § 180.407(c).

A2. The cargo tanks you describe have always required the 5-year interval timeframe. They are not eligible for the exception to requalify the cargo tank under a longer interval (i.e., 10 years) because they do not meet the criteria for eligibility.

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

Regulation Sections

Section Subject
180.407 Requirements for test and inspection of specification cargo tanks