Interpretation Response #24-0081
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: Infinite Composites, Inc.
Individual Name: Travis Alley
Location State: OK Country: US
View the Interpretation Document
Response text:
January 13, 2025
Travis Alley
Engineering Manager
Infinite Composites, Inc.
10738 E. 55th Pl.
Tulsa, OK 74146
Reference No. 24-0081
Dear Mr. Alley:
This letter is in response to your September 4, 2024, email and subsequent conversations with members of our staff requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to International Organization for Standardization (ISO) standards for pressure vessels. Specifically, you ask whether an ISO pressure vessel is permitted to exceed its working pressure due to environmental conditions, and whether testing parameters can be altered to reflect the expected environmental conditions.
We have paraphrased and answered your questions as follows:
Q1. You ask whether a pressure vessel designed and tested in accordance with the ISO 11119-3:2013 standard is permitted to exceed its working pressure when exposed to extreme temperatures while held in storage after the pressure vessels are no longer in transportation.
A1. For the purposes of the HMR, the answer is yes as long as the pressure vessel is not in storage incidental to transportation. The HMR apply to activities that involve the transportation of hazardous materials, and the loading, unloading, or storage of hazardous materials incidental to transportation. Therefore, during transportation, § 173.301(a)(8) requires that a cylinder's internal pressure at 55 °C (131 °F) may not exceed 5/4 of the service pressure of the cylinder and that the cylinder will not be liquid full at 55 °C (131 °F). However, provided that the pressure vessel has been designed, filled, and maintained in accordance with the HMR, there is no requirement that prevents the pressure vessel from experiencing increased pressures due to fluctuating ambient temperature when that pressure vessel has been placed in storage that is not incidental to a transportation.
We encourage you to look at other regulatory bodies for storage requirements such as the Occupational Safety and Health Administration, the U.S. Environmental Protection Agency, the Department of Defense, and state entities. We also encourage you to avoid subjecting a pressure vessel to temperatures in excess of the design parameters.
Q2. You ask whether the ambient cycle test in section 8.5.4.1 of the ISO 11119-3:2013 standard can be performed with a modified pmax calculation that reflects the expected temperature of 75 °C rather than the prescribed temperature of 65 °C.
A2. The answer is no. ISO specification pressure vessels must be constructed and tested in accordance with their respective Standard. In the case of the ISO 11119-3:2013 Standard, the Ambient Cycle test in section 8.5.4.1 must be followed as written with the pmax calculated based on a temperature of 65 °C.
However, if you wish to deviate from the design qualification testing requirements you may, in accordance with § 107.105, apply for a special permit to manufacture, mark, and sell a pressure vessel that is based on ISO 11119-3:2013, but for which pmax is measured at 75 °C. Please note that a pressure vessel manufactured under a special permit would be marked as a Department of Transportation Special Permit cylinder, not as an ISO pressure vessel.
I hope this information is helpful. Please contact us if we can be of further assistance.
Sincerely,
Steven Andrews
Acting Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division
107.105, 173.301(a)(8)