# Air Liquide Industrial U.S. LP — Hazardous Materials Safety Interpretation - **operation:** document - **citation:** 10-0079 - **title:** Air Liquide Industrial U.S. LP — Hazardous Materials Safety Interpretation - **source type:** guidance - **agency:** Pipeline and Hazardous Materials Safety Administration - **status:** guidance - **official:** true - **published on:** 2010-05-31 - **effective on:** Not available - **summary:** 10-0079 response to Air Liquide Industrial U.S. LP concerning 173.320. - **machine formats:** - **json:** https://regulus.evalyn.ai/document/phmsa-interpretation-10-0079.json - **markdown:** https://regulus.evalyn.ai/document/phmsa-interpretation-10-0079.md - **app url:** https://regulus.evalyn.ai/document/phmsa-interpretation-10-0079 - **source url:** https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretations/2010/100079.pdf **body:** <<>> U.S. Department of Transportation 1200 New Jersey Ave. SE Washington, D.C. 20590 Pipeline and Hazardous Materials Safety Administration MAY 26 2010 Mr. Steven Bilger Air Liquide Industrial U. S. LP 12800 West Little York Road Houston, TX 77041 Ref. No. 10-0079 Dear Ms. Bilger: This responds to your April 9, 2010 email requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) regarding a nitrogen, refrigerated liquid based refrigeration system designed for insulated transport trailers. Specifically you ask if the HMR apply to the 250 gallon cryogenic tank mounted to the bottom of a refrigerated trailer that is used to feed one or more heat exchangers within the trailer. The answer is no. Section 173.320(b)(2) provides an exception for atmospheric gases when used in operation of a process system; such as a refrigeration system. I hope this answers your inquiry. If you have further questions, please do not hesitate to contact this office. Since:~~ aries E. Betts C . ef, Standards Development Of 1 of Hazardous Materials Standards <<>> Drakeford, Carolyn (PHMSA) From: INFOCNTR (PHMSA) 10 10074 Sent: Friday, April 09, 20104:07 PM To: Drakeford, Carolyn (PHMSA) Subject: FW: Hazmat Information Center Feedback: Interpretations (Letters) Issued by PHMSA Carolyn, Attached is yet another written request for an interpretation. Thanks, Rob -----Original Message----From: PHMSA-Feedback [mailto:PHMSA-Feedback] Sent: Friday, April 09, 2010 3:44 PM To: PHMSA HM InfoCenter; PHMSA Webmaster Subject: Hazmat Information Center Feedback: Interpretations (Letters) Issued by PHMSA I would like to request a written letter of interpretation concerning the applicability of 49 CFR 173.320(b)(2) to a liquid nitrogen-based refrigeration system designed for insulated transport trailers. The refrigeration system consists of an insulated 250 gal cryogenic tank mounted to the bottom of the trailer which feeds one or more heat exchangers within the trailer. The flow of liquid nitrogen, the refrigerant, from the tank to the heat exhangers is due to tank pressure alone and is controlled by a network of valves, which either allow or prevent nitrogen flow. The transfer of heat from the trailer to the nitrogen causes the nitrogen to boil and vaporize within the heat exchanger coils. The heat exchanger coils feed a vent line which is piped outside of the trailer so as to avoid any nitrogen gas build up within the trailer. For the process to run effectively, a pressure of 30-60 psig is required within the liquid nitrogen tank during transport. Name: Stephen Bilger Organization: Air Liquide Industrial U.S. LP Email: stephen.bilger@airliquide.com Address: 12800 West Little York Road City: Houston Zip Code: 77041 Phone: 713-896-2247 FAX: 713-896-2390 1 - **truncated:** false - **body characters:** 2814