Interpretation Response #23-0065
Below is the interpretation response detail and a list of regulations sections applicable to this response.
Interpretation Response Details
Response Publish Date:
Company Name: W. R. Grace & Co.
Individual Name: Mr. Paul Errichetti
Location State: MD Country: US
View the Interpretation Document
Response text:
April 16, 2024
Mr. Paul Errichetti
Sr. Mgr., Fleet and Dangerous Goods
W. R. Grace & Co.
7500 Grace Drive
Columbia, MD 21044
Reference No. 23-0065
Dear Mr. Errichetti:
This letter is in response to your July 7, 2023, letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to pressure relief devices on specification Department of Transportation (DOT) 51 portable tanks. In your letter, you state that you have a fleet of DOT 51 portable tanks—comprised of both 250 gallon and 430 gallon capacities—with a test pressure of 300 psig and a maximum allowable working pressure (MAWP) of 200 psig. Specifically, you ask whether the required pressure relief devices may start to discharge at less than 110% of two-thirds of the test pressure.
The answer is no. As provided by § 178.275(g)(6)(ii)—and described in a previous Letter of Interpretation (LOI) Ref. No. 21-0035—the required pressure relief devices must be set to start to discharge at a nominal pressure of five-sixths of the test pressure for shells having a test pressure of not more than 4.5 bar (450 kPa) and 110% of two-thirds of the test pressure for shells having a test pressure of more than 4.5 bar (450 kPa). Since the applicable portable tanks have a test pressure of more than 4.5 bar (450 kPa), the start to discharge pressure for the pressure relief devices is required to be set at 110% of two-thirds of the test pressure (220 psig).
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
178.275(g)(6)(ii)