What does 49 CFR 173.5b (Portable and mobile refrigeration systems) require?

Short answer

49 CFR 173.5b requires that non-specification pressure vessels in portable and mobile refrigeration systems be designed, manufactured, and maintained according to the ASME Code, and have a maximum allowable work pressure (MAWP) of 250 psig. The aggregate total volumetric capacity of components within the refrigeration system may not exceed 2,500 gallons per vehicle.

The rule says

"Each pressure vessel must be designed, manufactured, and maintained in accordance with applicable requirements of the ASME Code (IBR, see 171.7 of this subchapter)." (49 CFR 173.5b(a)(1))

"Except as authorized in this section, each pressure vessel and associated piping must be rated at a maximum allowable work pressure (MAWP) of 250 psig." (49 CFR 173.5b(a)(2))

"The aggregate total volumetric capacity of components within the refrigeration system authorized for highway transportation in accordance with this section may not exceed 2,500 gallons per vehicle." (49 CFR 173.5b(a)(4))

In plain English

This regulation is about safely transporting refrigeration systems that contain hazardous materials like refrigerant gases or anhydrous ammonia. The rule requires that these systems be built and maintained to certain standards, like the ASME Code, to prevent accidents. It also sets limits on the pressure and capacity of the systems to minimize risks. Inspectors will check for compliance with these requirements during audits and inspections.

What to do

• Ensure that all non-specification pressure vessels in portable and mobile refrigeration systems meet the ASME Code requirements.
• Verify that the maximum allowable work pressure (MAWP) of each pressure vessel and associated piping is 250 psig or less.
• Calculate the aggregate total volumetric capacity of components within the refrigeration system to ensure it does not exceed 2,500 gallons per vehicle.
• Maintain records of compliance with these requirements for auditing and inspection purposes.