Fuel transport safety is a major concern that any company that moves and distributes fuel is concerned with. Various cargos require different types of tankers to safely get the cargo over the road within the Department of Transportation requirements. Fuel transport systems, depots, chemical transport companies, and gas transport companies need safe and reliable tankers to hold that material.
Non or low-pressure bulk liquid cargo tanks – MC-306 (DOT-406)
MC-306 (MAWP of 3 psi) and DOT 406 (MAWP of 4 psi) tankers are elliptical and typically transport gasoline or other flammable liquids. The insulated compartment tanks typically come in 3 compartments, 4 compartment, or 5 compartment configurations. These tankers have one or more domes or hatches and dome covers, generally one hatch per compartment in the tank.
- Typically carries gasoline (UN/NA 1203), diesel fuel (fuel oil), liquid fuel products, alcohol, and almost any other kind of flammable or combustible liquids. May sometimes carry non-flammable liquids (e.g., milk or molasses). May contain mild corrosives, but not strong corrosives. Cannot contain pressurized gases.
- Oval in cross-section, with blunt ends.
- Newer tanks are aluminum; older can be steel. The tank is divided into two to five compartments (usually three to four); in some cases, different products may be in different compartments (in most states, mixed loads are not permitted).
Contents are NORMALLY petroleum products, however, it could also contain water or milk
- Oval or a shaped cross-section
- Flat or nearly flat ends
- Aluminum is the primary material
- Usually multi-compartmented
- Separate manhole for each compartment
- There is a Fuel Transport Safety Emergency shutoff system on the driver’s side front
- There is rollover protection to prevent manholes from opening up on rollover.
- Average maximum capacity 9,000 gallons however some tanks are built to hold less.
- Trailer pressure has a maximum of 3PSI
- Different types of liners including a chlorobutyl rubber liner, or natural rubber lining, or Plasite linings, Chemline lining or Teflon
Low-pressure bulk liquid cargo tanks – MC-307 (DOT-407)
MC-307/DOT 407 tankers are usually horseshoe-shaped when viewed from the rear. They carry vegetable oils, syrups, and milk and they also carry solvents, lubricants, mild corrosives, etc. The insulated horseshoe-shape you see is the thin aluminum insulation outer shell. Some of these tankers are not insulated and can appear round with small ridges. The domes on these tankers are usually in the center of the tank but there can be more.
- Typically carries flammable or combustible liquids, acids, caustics, poisonous liquids.
- The maximum capacity is typically up to 6,000 gallons. Can be insulated or uninsulated:
- Uninsulated tanks are typically circular in cross-section. Typically, there are reinforcing rings around the tank. Tanks are aluminum or steel.
- Insulated tanks generally carry products that need to be kept either heated or cooled or products that need to be heated to be off-loaded. They are characteristically horseshoe-shaped when viewed from behind. They are comprised of an outer jacket, generally aluminum or steel, and an inner tank that may be lined (e.g., fiberglass).
Contents usually include: mild acids, water, milk, or combustible liquids
- Container Pressure can be up to 40 psi @ 70°F
- Horseshoe-shaped cross-section.
- Flat or slightly rounded ends
- Stainless steel is the primary material of construction
- The tanker may be insulated. Insulation or the outer shell may hide the horseshoe tank shape.
- The fill port is usually at the center top of the tank.
- The dispensing ports are usually at the bottom of the tank.
- A multi-compartmented tank has a separate loading port for each compartment.
- There is a Fuel Transport Safety Emergency Shutoff control on the driver’s side.
- Rollover protection to prevent manholes from opening up on rollover
- These tankers have an average maximum capacity of 6,000 gallons that can be handled rapidly at a loading facility or depot.
Corrosives Cargo Tanks – MC-312 (DOT-412)
- Typically carries strong corrosives, such as sulfuric or nitric acid. Typically carries acids, also may carry bases. Sometimes may carry flammable liquids (e.g., grain alcohol), poison·liquids, or oxidizing liquids. Cannot carry pressurized gases
- Circular in cross-section, with up to 10 reinforcing rings around the tank. May be very long. Often there is black, tar-like, corrosion protective coating around the manhole.
Contents can include: Corrosives, and high weighted (specific gravity) liquids
- Tank internal pressure is usually 35 to 50 psi. Because of pressurization, exterior strengthening rings are used for containment.
- The tank is usually lined with rubber or plastic.
- A cross-section of this type of tank appears round.
- These tanks are usually Stainless steel.
- Some of these tanks may have an insulated outer shell.
- The dispensing valves are usually at the rear of the tank at the bottom.
- If the tank has multiple compartments, each compartment will have a loading port.
- There is an emergency fuel transport safety shutoff mechanism.
- These tankers have a cigar shape and a long, small diameter.
- The average maximum capacity of these type of tanks range from 4,000 to 7,000 gallons
Internal Pressure Specifications
|MC 300, 301, 302, 303, 305, 306||20.7 kPa (3 psig) or the designed pressure of the tank, whichever is greater|
|MC 304, 307||275.8 kPa (40 psig) or 1.5 times the design pressure of the tank, whichever is greater|
|MC 330, 331||1.5 times either the maximum allowable operating pressure or the re-rated pressure, whichever applies.|
|MC 338||1.25 times either the maximum allowable operating pressure or re-rated pressure, whichever is applies.|
|DOT 406||34.5 kPa (5 psig) or 1.5 times the maximum allowable operating pressure (MAWP), whichever is greater.|
|DOT 407||275.8 kPa (40 psig) or 1.5 times the MAWP, whichever is greatest.|
|DOT 412||1.5 times the MAWP, (Maximum Allowable Operating Pressure)|
MAWP (Maximum Allowable Operating Pressure)
Compressed Gas Cargo Tanker – MC-331
- Circular appearance cross-section.
- This tank has rounded ends.
- This type of tank is constructed with a single shell that is made from carbon steel.
- Tanker valves, gauges, and piping are protected to limit damage from rollovers.
- In most cases, these tanks are painted white to prevent damage due to the sun’s UV rays.
- Tank Pressure is rated at – 100 to 500 psi.
- Even more, the tanker contents are usually gases that are liquefied by the application of pressure.
- Tank Capacity in most cases ranges from 3,500 gallons for bobtail tanker to 11,500 gallons for highway transporters.
Contents: Gases and Ammonia
- Liquefied Butane gas
- Anhydrous Ammonia
Cryogenic Cargo Tank – MC-338
- These tanks are designed to hold cryogenic liquids that hold a temperature of at least -130°F.
- Tanks have a cylindrical shape with a “box cabinet” on the rear of the tank.
- These tankers are designed like a Thermos bottle. There are 2 cylinders and one cylinder is inside the other cylinder.
- The area between the two cylinders is a vacuum which creates an airtight environment.
- Visible vapors escape from the vent on the rear cabinet area of the cylinder. However, his is normal.
- Internal tank pressures range from 23.5 to 500 psi with the lower end being the norm.
- Very high BLEVE potential (BLEVE – boiling liquid expanding vapor explosion, which occurs when the pressurized liquid inside of a vessel, such as a propane tank, reaches temperatures higher than that liquid’s boiling point.)
Tank Contents Include:
- Substances that are not be liquefied by applied pressure. These substances have to be supercooled to become liquid form.
- Examples: Liquid oxygen, hydrogen, nitrogen, and carbon dioxide
High-pressure Tube Tank – Carry gasses that can not be liquefied with the application of pressure.
- This tanker contains multiple tubes.
- Each tube is a separate container.
- Each tube is protected with a thermal plug. The thermal plug is designed to melt in a fire. This action relieves internal pressure and is a key element of fuel transport safety.
- In addition, Tubes are individually controlled in the rear compartment
- Off-loaded by “cascade style” (same method as used to fill SCBA bottles)
- Pressures of 4,000 to 6,000 psi per tube
- Usually 9 to 12 tubes per trailer
- High-pressure tube rail cars are of the same design as these styles of highway cargo tanks
- Gases that can not be liquefied pressure applications.
- Examples include Helium, nitrogen, oxygen, and argon gasses.
Dry Bulk or Pneumatic Hopper Trailer
A dry bulk or pneumatic hopper is a trailer that a metal cylinder with a series of cone-shaped hoppers at the bottom and manholes at the top. At the bottom of each hopper is a valve, opening into a pipe that runs below the trailer. It’s called a pneumatic trailer below contents are unloaded by air pressure that blows product out of the hopper through a pipe that’s attached to the bottom valve under the hopper. Dry bulk materials are gravity loaded from a silo or railcar via a loading arm through the top manhole.
- Container Pressure can be up to 22 psi
- calcium carbide, oxidizers, corrosive solids, cement, plastic pellets, or fertilizers.
Tanker Truck Safety Features
Baffles – Baffles are placed inside tanks to prevent maximum forward and rearward motion of the stored liquid within the tank. When a truck that is hauling a high viscous material comes to a halt, the liquid in the tank generates a great deal of force due to the forward motion of the cargo. To distribute the force evenly and to limit the transfer of energy, Installed vertical large-holed plates or cages divide and slow the flow of moving liquid.
Liner – Liners are designed to increase the operational time of a tank. Tank liners protect steel, stainless steel, and aluminum tanker trailers from the effects of corrosive materials. Many tankers haul solvents and hydrochloric acids with concentrations greater than 20% making a liner is an absolute requirement.
Skully – A skully system provides overfill protection and grounding verification for tanker trucks. Tankers that haul petroleum and liquid chemicals need automatic and continuous self-checks. Sensors in a skully system provide automatic and continuous self-checking circuitry. This too is a key component in Fuel Transport Safety.
Pump – Pumps are the mechanisms needed to dispense, mix, and blend, heavy, viscous liquids carried in tankers. Pumps are manufactured of various materials and are installed in the tankers to accommodate the type of load. For example, Stainless steel pumps are necessary when working with corrosive unstable chemicals. This is another element of fuel transport safety that cannot be overlooked.
Vapor Recovery Systems – Vapor recovery systems are installed on tankers and at loading platforms that handle cargos that should not be dispersed into the atmosphere. Vapor recovery systems capture errant vapors that happen during the loading or unloading of a product however they return them to the cargo hold. Good vapor recovery systems save money by reducing lost product.