CDL Tanker key terms

A commercial motor vehicle designed to carry liquid or gaseous material in a tank that is attached to the vehicle, either permanently or as a portable tank or tank container.

A CDL endorsement that allows a driver to operate a tank vehicle. It is required when the vehicle is designed to carry 1,000 gallons or more of liquid, or several tanks totaling that amount.

A tank permanently attached to a motor vehicle and used to carry liquid or gaseous cargo. It may be a single shell or may be divided into separate compartments.

A tank that is not permanently attached to the vehicle and can be loaded on or removed, often holding 1,000 gallons or more of liquid.

A cargo tank built to a federal design standard, such as DOT 406, that sets shell thickness, fittings, and testing requirements for the types of lading it may legally carry.

A tank fitted with internal partitions that slow the front-to-back and side-to-side movement of liquid. Baffles reduce surge but do not stop it completely.

A tank with no internal partitions, so liquid can run freely from one end to the other and create strong surge when the vehicle changes speed.

A separate section inside a cargo tank, with its own fill opening and outlet valve, used to carry different products or to divide the load for stability.

The hinged cover on top of a tank compartment that is opened for top loading or inspection and must be closed and sealed before the vehicle moves.

A valve or opening that lets air and vapor enter or leave the tank as the liquid level changes, so pressure or vacuum does not build up inside.

A soft ring or seal fitted between mating surfaces, such as a dome cover or hose coupling, that stops liquid or vapor from leaking out.

The flexible line used to move product between the tank and storage tanks or other equipment. It must be checked for cuts, soft spots, and worn fittings before each use.

A valve mounted inside the tank at the outlet that closes automatically when the hose or piping is broken or pulled away, limiting how much product escapes.

A valve at the tank outlet or loading rack that can be closed quickly by hand or by a remote control to stop the flow of product during an emergency.

The piping that connects several tank compartments to one common loading or unloading connection, with valves that control which compartment is being used.

The date marked on the tank showing when its required pressure or leak test was completed. An overdue test makes the vehicle out of service and illegal to drive.

The systematic check of the tank shell, hoses, fittings, valves, tires, and brakes done before driving, meant to catch leaks and defects before they cause a breakdown or spill.

The shifting of liquid inside a partly filled tank when the vehicle speeds up, slows down, or turns. The moving weight pushes the truck and makes steering and stopping harder.

The empty space deliberately left at the top of a tank so the liquid has room to expand as it warms. Too little outage can cause overflow or a split tank.

The point where the weight of the vehicle and its load balances. A loaded tank raises this point, so the vehicle leans more in turns and rolls over more easily.

A crash in which the vehicle tips onto its side or roof. Tank vehicles are prone to rollover because of the high center of gravity and the shifting weight of the liquid.

Liquid sloshing across the width of the tank during a turn, which pushes the vehicle toward the outside of the curve and increases the chance of a rollover.

A loss of traction in which the tires slide instead of rolling, usually caused by braking too hard, driving too fast, or steering suddenly on a slippery surface.

The total distance travelled from the moment the driver decides to stop until the vehicle is fully stopped. Liquid loads increase it because surge pushes the truck forward.

The gap kept behind the vehicle ahead. For a tank vehicle it should be at least one second for every ten feet of vehicle length, plus extra room for liquid surge.

Filling the tank through connections at the bottom, which reduces static buildup and vapor release and lets more than one compartment be loaded at a time.

Filling the tank through the open dome on top, which exposes product to the air and requires extra care with vapors, spills, and static electricity.

A system that captures the vapors pushed out of a tank during loading and returns them to the storage tank instead of letting them escape into the air.

Connecting the tank vehicle and the loading facility with a cable so static electricity can flow between them and cannot spark when product starts to flow.

Connecting equipment to the earth, usually with a ground cable or rod, so that static electricity drains away safely instead of building up to a spark.

An electric charge that builds up as liquid moves through pipes, hoses, or filters. If it discharges as a spark near flammable vapor, it can start a fire or explosion.

A liquid that gives off ignitable vapor at normal working temperatures, generally one with a flash point at or below 140 degrees Fahrenheit (60 degrees Celsius).

The lowest temperature at which a liquid gives off enough vapor to form a mixture that will ignite if a flame or spark is present.

A diamond-shaped warning sign attached to the vehicle that shows the hazard class of the material being carried, such as flammable liquid.

The paperwork that describes a hazardous materials shipment, including the proper shipping name, hazard class, quantity, and an emergency contact telephone number.

Written or guidebook information carried with a hazardous materials load that tells emergency responders what the material is and how to handle a spill, fire, or exposure.

A CDL endorsement required to drive a vehicle carrying hazardous materials in amounts that need placards. It requires a background check and a written knowledge test.

Putting more product into a tank than its marked capacity allows, which leaves too little outage for expansion and can push liquid out through the vent.