DOT Trailer Codes for Cryogenic and CO2

Christian Spaccarotella
6 Minutes

LGT specializes in Industrial Gas Transportation, meaning we haul a wide range of liquefied gases. The equipment we use at LGT is reliant on what type of gas is being transported. Tractors can all vary depending on preferences, but the real thing to consider is what tanker/trailer to use. If you are trying to get into the cryogenic or Industrial Gas Transportation industry, these are the main types of tankers to use when hauling hazardous and non hazardous materials.


For transportation of compressed gases, MC 331 cargo tank is the option. Generally speaking, this trailer must be a DOT specification tank, so it must always have a trailer data plate that displays information on the manufacturer, capacity and construction material. Here's its requirements:

  • Must be made of steel or aluminum however, if aluminum is used, the tank can be insulated or non-insulated, and the hazardous material must be compatible (some products are corrosive with certain metals).
  • Must have an outer jacket if the tank is insulated and used to transport a flammable gas or pressurized gas.
  • Vapor pressure inside the vessel ranges between 100-500 psi.
  • If insulated, must have a barrier of at least 2-4 inches depending on combustibility and material .
  • Every uninsulated cargo tank attached to a motor vehicle unless covered with an aluminum or stainless steel jacket, must be painted white, aluminum or similar reflective color on the upper two-thirds of the cargo tank.
  • All valves, fittings, pressure relief devices, and other accessories on the tank must be protected against crashes and rollovers.
  • A single shell carbon steel construction with circular cross-section, and rounded ends.
  • The capacity of the tanks range from 2,500 gallons and 11,500 gallons, depending on type of vehicle and trailer.

The MC 331 is only used for gases that are liquefied under extremely high pressures such as:

  • Butane
  • Propane (LNG)
  • Chlorine
  • Anhydrous Ammonia
  • Liquid Carbon Dioxide (CO2)


This trailer is primarily used for Cryogenic liquids. The DOT defines cryogenic liquids as the substance must be at least -130 degrees F. Essentially, cryogenic liquids are produced by a combination of extremely low temperatures and pressure, rather than extreme pressure alone. These trailers can be a specification tank or non-spec tanks. Here's the trailer's requirements:

  • Cargo tank must consist of welded inner vessel with a welded outer shell or jacket, with insulation and vacuum between the two. This space is called the annular space.
  • Each exterior tank must be insulated with material compatible with the lading. The jacket or insulation must be sealed to prevent moisture from coming into contact with the insulation.
  • Cylindrical shape with "box cabinet" on rear of tank.
  • All piping, valves and fittings must be grouped in the smallest practicable space and protected from damage.
  • Air pressure within the inner vessel ranges between 23.5 psi to 500 psi.
  • In order to be a non-spec tank, categorized as a CGA 341, a pressure regulator must be installed on the trailer keeping the pressure of the trailer under 25 psi.
  • CGA stands for “Compressed Gas Association”

This trailer can contain substances that require both extreme temperatures and pressures such as:

  • Liquid Oxygen
  • Liquid Hydrogen
  • Liquid Argon
  • Liquid Nitrogen

DOT406 (MC 306)

This trailer typically contains Petroleum products, milk, or water. Here are the trailer requirements:

  • Operating pressure must be no lower than 2.65 psi and no higher than 4 psi.
  • Aluminum is the main material for construction.
  • Oval shaped cross section and flat or nearly flat ends.
  • Each cargo tank with capacity greater than 400 gallons must be accessible through manhole at least 15 inches in diameter.
  • Must have manhole for each compartment.
  • Multi-Compartmented.
  • If the thickness of the shell is less than three-eighths of an inch, it must be reinforced with bulkheads, baffles, ring stiffeners or any combination in addition to the tank heads.
  • Must be protected against crashes or rollovers with accident damage protection devices to prevent manholes from opening.
  • Capacity ranges from more than 0 to 14,000 gallons.

DOT407 (MC 407)

DOT 407 Trailer can also carry water and milk, but it also has the capacity to haul combustible liquids and mild acids. Here are the trailer requirements:

  • Circular cross section.
  • Air pressure ranges anywhere below 40 psi.
  • Primary construction material is stainless steel.
  • Can be both insulated and not.
  • Must be protected against crashes or rollovers with accident damage protection devices to prevent manholes from opening.
  • Max capacity is typically around 6,000 gallons.
  • Can be multi-compartmented or not.
  • Manway near top.
  • Emergency shut off on drivers side front.

(Liquid Partners Group)

DOT412 (MC 312)

DOT 412 typically carries corrosive materials and specific gravity (high weight) liquids. Here are the trailer requirements:

  • Air pressure capacity ranges from at least 5 psi to at most 25 psi.
  • Circular cross section.
  • Stainless steel is the primary material, but can also be aluminum.
  • Can be insulated or not.
  • Manway near top.
  • Emergency shut off on drivers side front.
  • Tank is long and skinny tube with reinforcements visible on exterior.

(Liquid Partners Group)

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