Ask X3What does 49 CFR 173.302a (Additional requirements for shipment of non-liquefied (permanent) compressed gases in specification cylinders) require?
Generated guidance. Confirm the source and its applicability before you act. How we check sources.
According to 49 CFR 173.302a, non-liquefied (permanent) compressed gases (except gases in solution) for which filling requirements are not specifically prescribed in § 173.304a must be shipped in specific specification cylinders subject to detailed filling requirements, including general rules in §§ 173.301, 173.301a, 173.302, and 173.305.
As a motor-carrier owner, you must ensure that your shipments comply with the cylinder specifications and operational rules outlined in the regulation, which include:
* Authorized Cylinder Types: Use only authorized DOT specification cylinders (such as DOT 3, 3A, 3AA, 3AL, 3B, 3E, 4B, 4BA, 4BW, 4E, 3HT, 39, 3AX, 3AAX, and 3T), depending on the specific gas type.
* Aircraft-Only Cylinders: DOT 3HT cylinders are strictly for aircraft use, limited to non-flammable gases, have a maximum 24-year service life from manufacture, and require specific frangible disc pressure relief devices and packaging.
* Volume Limits on Flammable/Special Gases: DOT 39 cylinders carrying Division 2.1 flammable gas cannot exceed an internal volume of 1.23 L (75 in³), with specific limits also applying to chemicals under pressure.
* Methane and Special Gas Purity: Methane used in DOT 3AX, 3AAX, and 3T cylinders must be a non-liquefied gas with a minimum purity of 98.0 percent and be commercially free of corroding components (DOT 3T cylinders are not authorized for hydrogen).
* Aluminum Cylinder Restrictions: Aluminum cylinders (DOT 39, 3AL, and 4E) are authorized for oxygen only under the conditions specified in § 173.302(b).
* Capacity and Pressure Caps for DOT 4E: DOT 4E cylinders with a maximum capacity of 43 L (11 gal) must have a minimum rating of 240 psig and be filled to no more than 200 psig at 21 °C (70 °F).
* Special 10% Over-Pressure Filling Limits: Certain cylinders (like DOT 3A, 3AX, 3AA, 3AAX, and 3T) may be filled to a pressure 10% above their marked service pressure, provided they meet strict testing, elastic expansion (water jacket method), wall stress limitations, visual examination standards, and display a plus sign (+) following the test date. Similar over-fill allowances apply to hydrogen mixtures in specific post-1945 cylinders.
* Carbon Monoxide Rules: Carbon monoxide must use specified cylinders with a minimum service pressure of 1800 psig, and filling pressures are strictly capped based on cylinder type and gas condition (dry/sulfur-free). DOT 3AL cylinders for carbon monoxide are restricted to motor vehicle, rail car, or cargo-only aircraft transport.
* Diborane and Fluorine Rules: Diborane and diborane mixtures must use DOT 3AL1800 or 3AA1800 cylinders with a maximum 7 percent filling density and protected valve assemblies. Fluorine must use specification 3A1000, 3AA1000, or 3BN400 cylinders without pressure relief devices, equipped with valve protection caps, charged to no more than 400 psig at