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Interpretation Response #25-0004

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

Interpretation Response Details

Response Publish Date:

Company Name: Bancroft Hinchey Ltd.

Individual Name: Kevin Turner

View the Interpretation Document

Response text:

June 24, 2025

Kevin Turner
Training & Assurance Manager
Bancroft Hinchey Ltd.
Unit 7A, Hartley Business Park
Selborne Road
Alton, Hampshire, GU343HD

Reference No. 25-0004

Dear Mr. Turner:

This letter is in response to your January 10, 2025 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to pressure tests and system checks performed on cylinders. You state that the pressure test requirement in § 180.205(g) of the HMR permitting a "system check" to be performed at a pressure up to 90% of test pressure conflicts with instruction offered in the Compressed Gas Association (CGA) publication, C-1, "Methods for Pressure Testing Compressed Gas Cylinders," which is incorporated by reference in § 180.205(g). Specifically, CGA C-1 provides instruction for a cylinder to be pressurized to less than 90% of the minimum test pressure. You provide an example of a DOT 3AA cylinder with a service pressure of 1800 psi, which is pressurized during a system check to 2700 psi1 (i.e., exactly 90% of the minimum required test pressure). Specifically, you ask, would pressurizing the cylinder to 90% of the test pressure rather than below be considered a "system check" instead of a test?

1 Table 1 to paragraph (a) of § 180.209 – DOT 3AA cylinders must have a minimum test pressure of 5/3 times service pressure, except non-corrosive service (see § 180.209(g)). As such, 1800 psi x 5/3 = 3000 psi.

Yes. Based on the example you provided, it is the opinion of this Office that what you describe would be considered a system check. While § 180.205 requires pressure testing in accordance with CGA C-1, § 180.205(g) allows a system check to be performed at or below 90% of test pressure. Section 180.205(g) does not require adhering to CGA C-1 which prescribes a system check below 90% of test pressure. However, because any pressurization that exceeds 90% would be considered a test, performing a system check at pressures below 90% is more conservative as it ensures that a cylinder is not inadvertently pressurized over 90% of test pressure (e.g., due to minor gauge tolerance differences).

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

Sincerely,

Dirk Der Kinderen
Chief, Standards Development Branch
Standards and Rulemaking Division

§ 180.205(g), § 180.209, § 180.209(g)

Regulation Sections