Tank vehicles

A commercial vehicle built to carry liquid or gas in a large tank.

Tankers carry milk, fuel, chemicals, or gas, and the cargo moves inside the tank, so the truck handles differently. The legal definition is a tank of more than 119 gallons, with 1,000 gallons or more in total. Hauling one usually needs the N endorsement.

Liquid sloshing in a partly filled tank when speed or direction changes.

Brake, and the liquid rushes forward, then slams back. The wave pushes the truck the way it moves. On ice it can shove a stopped truck into the intersection.

A perforated wall inside a tank that slows the liquid's forward surge.

Baffles are bulkheads with openings. Liquid still passes through, but slowly, so the forward surge is weaker. They do nothing for side-to-side surge.

A solid wall that divides a tank into separate smaller compartments.

Unlike a baffle, a bulkhead has no holes. Each compartment can hold a different liquid. Loading one end heavier than the other upsets the vehicle's balance.

A tank with nothing inside to slow the liquid; an unbaffled tank.

Food-grade tankers, like milk trucks, are smooth bore because baffles are hard to clean. The surge inside is strongest. Starting and stopping need extra care.

Space left empty in a tank so warming liquid can expand.

Never fill a tank to the top. Liquids grow when they get warm. Different liquids need different outage, and you must know the figure for your load.

Not the same as: Not a power outage; in tanker language it is the headspace left in the tank.

The balance point of a vehicle's weight; higher means easier rollover.

Stack cargo high and the balance point rises. A tall liquid load raises it most. A high center of gravity means slow down more for curves and ramps.

The N endorsement a CDL needs to drive a tank vehicle.

You earn it by passing the tank knowledge test. The cargo does not have to be hazardous; milk and water count. Hazmat in a tank needs both N and H, written X.