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 #10-0077 ([Thunderbird Cylinder] [Mr. Fred A. Nachman])

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

Interpretation Response Details

Response Publish Date:

Company Name: Thunderbird Cylinder

Individual Name: Mr. Fred A. Nachman

Location State: AZ Country: US

View the Interpretation Document

Response text:

September 14, 2011




Mr. Fred A. Nachman


Thunderbird Cylinder

4209 E. University Drive

Phoenix, AZ 85034-7315

Ref. No.: 10-0077

Dear Mr. Nachman:

This responds to your letter requesting clarification of the requirements concerning the tare weight of liquefied petroleum gas (LPG) cylinders under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180).

Q1. Does a low pressure (LPG) cylinder being visually inspected need to have its valve/PRD removed to verify there is no liquid inside it that would result in improper tare weight verification?

A1. No. A cylinder conforming to §180.209 used exclusively in LPG service may be given an external visual inspection in lieu of a hydrostatic test. No measurement of the tare weight is required for the external visual inspection. When the cylinder exhibits corrosion, the cylinder must be further examined for condemnation. The cylinder must be examined by measuring tare weight in accordance with CGA C-6, (1). The cylinder must be empty. The tare weight is measured with the valve/ PRD connected. Cylinders exempt from tare weight measurement must be examined by measuring wall thickness in accordance with CGA C-6, (2), (3), or (4).

Q2. At the time of requalification, should the pressure relief device (PRD) be changed?

A2. No. There is no regulatory requirement to change the PRD at the time of requalification. Pressure relief devices must be tested for leaks before a filled cylinder is shipped in accordance with §173.301(a)(2) and (3).

Q3. Should it even be an option to hydrostatically test or steam clean LPG cylinders when ethyl mercaptan exposed to water/moisture is corrosive?

A3. Cylinders containing LPG in accordance with §180.209(g) may be given an external visual inspection in lieu of a hydrostatic pressure test. This would avoid adding moisture to the cylinder. If steam cleaning is used, it is the responsibility of the filler to make sure the cylinder is dry before filling with a hazardous material, if moisture is dangerous to the cylinder (§173.301(d)).

I hope this information is helpful. If we can be of further assistance, please contact us.


Ben Supko

Chief, Standards Development Branch

Standards and Rulemaking Division

180.209, 173.301

Regulation Sections

Section Subject
173.301 General requirements for shipment of compressed gases and other hazardous materials in cylinders, UN pressure receptacles and spherical pressure vessels
180.209 Requirements for requalification of specification cylinders