The qualification and testing of cylinders

August 3, 2018

Reference No. 18-0010

This letter is in response to your January 13, 2018, email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the qualification and testing of cylinders. Specifically, you ask whether the elastic expansion (EE) and permanent expansion (PE) percentage ratio pass/fail limits are per test or cumulative. In your email, you provide the following example—

A cylinder is presented for inspection that has a 5-year requalification period and a maximum 5% PE-to-EE ratio, as illustrated in the following table:

Inspection Timeline Per Test PE/EE Cumulative PE/EE Per Test
Pass/Fail Decision Cumulative Pass/Fail Decision
First inspection 1.5% 1.5% PASS PASS
5-year inspection 1.1% 2.6% PASS PASS
10-year inspection 1.8% 4.4% PASS PASS
15-year inspection 1.4% 5.8% PASS FAIL
20-year inspection 1.2% 7.0% PASS FAIL

To answer your question, the EE and PE percentage ratio pass/fail limits are per test and not cumulative. Therefore, the cylinder in your example would also pass the 15-year and 20-year tests.

I hope this information is helpful. Please contact us if we can be of further assistance.

Sincerely,

T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division