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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation

Interpretation Response #13-0013 ([Global Products and Services, Baker Hughes] [Mr. Aubrey R. Campbell])

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

Interpretation Response Details

Response Publish Date:

Company Name: Global Products and Services, Baker Hughes

Individual Name: Mr. Aubrey R. Campbell

Location State: TX Country: US

View the Interpretation Document

Response text:

April 10, 2013



Mr. Aubrey R. Campbell
Senior Dangerous Goods Safety Advisor
Global Products and Services, Baker Hughes
2001 Rankin Road
Houston, TX 77073

Ref. No. 13-0013

Dear Mr. Campbell:

This responds to your December 10, 2012 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to accumulators.  In your letter, you describe and provide a picture illustrating two accumulators that are part of a "Thumper Unit" that is used at well drilling sites as an integral component of the oilfield operation.  Each accumulator is offered for transport pre-charged with nitrogen gas to a maximum pressure of 2,000 psig (at 70°F).  Additionally, each has a manufacturer's burst pressure rating of 12,000 psig, which is six times greater than the maximum pre-charged pressure.  Based on this information, it is your understanding that the "Thumper Unit" is excepted from the requirements of the HMR as specified in § 173.306(f).

Your understanding is correct.  In accordance with § 173.306(f)(1), accumulators installed in motor vehicles, construction equipment, and assembled machinery and designed and fabricated with a burst pressure of not less than five times their charged pressure at 70 °F., when shipped, are not subject to the requirements of the HMR.  Based on the information you provided, the "Thumper Unit" meets the conditions for exception from the HMR.

I hope this information is helpful.  If you have further questions, please contact this office.


Robert Benedict
Chief, Standards Development Branch
Standards and Rulemaking Division


Regulation Sections

Section Subject
173.306 Limited quantities of compressed gases