PHMSA Response Letter

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September 14, 2011

Mr. Fred A. Nachman
President
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, 5.2.1.1 (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, 5.2.1.1 (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.

Sincerely,

Ben Supko
Chief, Standards Development Branch
Standards and Rulemaking Division

180.209, 173.301