What does 49 CFR 173.304b (Additional requirements for shipment of liquefied compressed gases in UN pressure receptacles) require?

As Ask X3, your fleet-compliance assistant, here is what is required according to 49 CFR 173.304b:

* General Requirements: Liquefied gases and gas mixtures must be offered for transportation in UN pressure receptacles following the rules in this section, § 173.304, and the general requirements for UN pressure receptacles found in §§ 173.301 and 173.301b.

* Filling Limits: You cannot exceed the maximum filling ratio prescribed in this section and the applicable ISO standard. You can check compliance using Table 2 of P200 of the UN Recommendations, or determine the limits based on the specific type of gas:

* *High pressure liquefied gases:* The settled pressure filling ratio at 65 °C (149 °F) must not exceed the test pressure of the receptacle (or you can use the formulas in (3)(b) of P200).

* *Low pressure liquefied gases:* The maximum mass in kilograms of contents per liter of water capacity must be $\le$ 95 percent of the liquid phase at 50 °C, the receptacle must not be liquid full at 60 °C, and the test pressure must equal or exceed the vapor pressure of the liquid at 65 °C (or you can use the formulas in (3)(c) of P200).

* *Liquefied gases charged with compressed gases:* Account for both components in internal pressure calculations. Maximum mass per liter of water capacity cannot exceed 95 percent of the liquid phase density at 50 °C (122 °F), the liquid phase cannot completely fill the receptacle at any temperature up to 60 °C (140 °F), and the internal pressure at 65 °C (149 °F) cannot exceed the test pressure (or use the procedure in (3)(e) of P200).

* Tetrafluoroethylene, stabilized (UN1081): Must be packaged in a pressure receptacle with a minimum test pressure of 200 bar and a working pressure of no more than 5 bar.

* Fertilizer ammoniating solution with free ammonia (UN1043): Is not authorized to be transported in UN tubes or MEGCs.