Interpretation Response #09-0265 ([Air Liquide America Specialty Gases LLC] [Mr. Ralph Diaz])
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Air Liquide America Specialty Gases LLC
Individual Name: Mr. Ralph Diaz
Location State: TX Country: US
View the Interpretation Document
Response text:
January 27, 2010
Mr. Ralph Diaz
Air Liquide America
Specialty Gases LLC
2700 Post Oak Blvd.
Houston, TX 77056
Ref. No. 09-0265
Dear Mr. Diaz:
This responds to your e-mail regarding the reuse of a cylinder under the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180). Specifically, you ask under what condition the HMR authorize a cylinder previously used in carbon monoxide (CO) service to be refilled with a high-purity gas such as helium, argon, or hydrogen. Additionally, you ask whether the HMR define the term "dry," as used in § 173.302a(c).
When promulgating regulations regarding the filling and transportation of cylinders used exclusively in CO service, we did not foresee the need to codify any condition or minimum qualification for the continued use of such cylinders in another gas service. Although the HMR do not prohibit such practice, PHMSA strongly discourages it for safety reasons. For example, the moisture in CO may cause internal micro-cracking of the cylinder. Such cracking may not be detected through internal visual inspection or hydrostatic testing. Therefore, until a regulatory solution is adopted, we recommend the following tests be performed, at a minimum, if considering a change in gas service:
1. Proof pressure test equal to test pressure of the cylinder with a minimum of one (1) minute hold time; and
2. 100% side wall ultrasonic examination (UE) using shear wave with accept/reject criteria of 5% of design minimum wall thickness.
Ten percent overfill of the cylinders is not recommended. The term "dry," as used in § 173.302a(c), is not defined in the HMR. For the purposes of § 173.302a(c), "dry" means a gas having a dew point at or below -46.7 °C (-52 °F) at 101.3 kPa (14.7 psia) (one atmosphere).
Thank you for bringing this matter to our attention. If we can be of further assistance, please contact this office.
Sincerely,
Hattie L. Mitchell
Chief, Regulatory Review and Reinvention
Office of Hazardous Materials Standards
173.302a(c)