What does 49 CFR 173.33 (Hazardous materials in cargo tank motor vehicles) require?

Based on 49 CFR 173.33, the regulations for hazardous materials in cargo tank motor vehicles require the following:

* General Requirements: You cannot offer or accept a hazardous material for transport in a cargo tank unless authorized. You cannot mix two or more materials in the same tank if it creates an unsafe condition (like a fire, explosion, pressure/heat increase, or toxic vapors). You also cannot fill and offer a specification cargo tank if its periodic retest or reinspection is past due (unless it was filled before the due date, or the cargo tank is supplied by a motor carrier who is not the person offering the material for transport).

* Loading Requirements: Do not load a hazardous material if it will dangerously react with, adversely affect the integrity of, or severely corrode the tank. Avoid chemical combinations with tank residues or contaminants that could cause an explosion, fire, pressure increase, or toxic vapors. Do not use air pressure above atmospheric to load or unload any lading that could create an air-enriched mixture within its flammable range. To prevent cargo tank rupture, your loading or unloading rate must be at or below the rate on the tank's specification plate (or limited so the pressure does not exceed 130% of the Maximum Allowable Working Pressure [MAWP] if no rate is marked).

* Maximum Lading Pressure: Before loading and offering a specification cargo tank, you must confirm it conforms to the required specification and that its MAWP is greater than or equal to the highest pressure calculated for your specific type of lading (such as compressed gases, cryogenic liquids, or liquid hazardous materials based on vapor pressure, static head, and gas padding). Division 6.1 (poisonous liquid) Packing Group I or II materials must be loaded in a cargo tank with an MAWP of 25 psig or greater.

* Relief Systems: Non-reclosing pressure relief devices are generally not allowed unless used in series with a reclosing device (with specific exceptions for older or certain tank types). Tanks transporting liquid hazardous materials with a gas pad must have a pressure relief system providing the required venting capacity.

* Product Piping: DOT specification cargo tanks transporting Division 6.1 (poisonous liquid), liquid oxidizers, liquid organic peroxides, or corrosives (corrosive to skin only) cannot transport hazardous material left inside the product piping unless the vehicle is equipped with proper bottom damage or accident damage protection devices. This does not apply to a standard drained residue.