tank vehicle
vehículo tanqueA 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.
On the test
Questions ask what makes tank vehicles special to drive, the most important inspection item, and what shape of tank is most stable.
Appears in 61 test questions
See 56 questions on the Tanker testDiffers by state: The capacity definition is uniform in all manuals: an individual tank of more than 119 gallons and a total of 1,000 gallons or more. The tanks may be permanently or temporarily attached. Some manuals (GA, ME, PA, WY) still also print the pre-2011 rule, under which any permanently mounted cargo tank counted. Legacy tables in ID, MI, VT and WV do the same. Maryland's plain-language text joins the two limits with 'or'. A question that turns on a small permanently mounted tank gets opposite answers in those manuals.
Example: Rolling up to a red light with a half-full milk tanker, you brake early and keep steady pressure on the pedal.
Also called: tanker, tank vehicles, tanker truck
liquid surge
oscilación de líquidoLiquid 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.
On the test
Questions ask what causes liquid surge, how it affects handling, how baffles change it, and how to control it.
Appears in 20 test questions
See 19 questions on the Tanker testExample: Stopped on a slick downhill ramp, you keep the brakes firmly applied until the wave inside the tank has settled.
Diagram coming
Also called: surge
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.
On the test
Questions ask what baffles are, which surge they control and which they do not, and why some tanks have none.
Appears in 24 test questions
See 23 questions on the Tanker testExample: Driving a baffled fuel tanker, you still slow well before the curve because the liquid can swing sideways.
Diagram coming
Also called: baffles, baffled tank
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.
On the test
Questions ask how bulkheads differ from baffles and what the driver must watch when filling or emptying the compartments.
Appears in 13 test questions
See 13 questions on the Tanker testExample: Unloading only the rear compartment at the first stop, you check that the front axle is not now carrying too much.
Diagram coming
Also called: bulkheads
smooth bore
tanques de fondo lisoA 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.
On the test
Questions ask what a smooth bore tank is, what cargo it usually carries, and when to be most careful driving one.
Appears in 9 test questions
See 9 questions on the Tanker testExample: Hauling a smooth bore load of juice, you ease off the clutch at every light to keep the wave small.
Also called: smooth bore tank, unbaffled tank
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.
Does not mean: Not a power outage; in tanker language it is the headspace left in the tank.
Example: Loading a tanker on a cold morning, you stop below the top because the product will swell in the afternoon heat.
Diagram coming
Also called: ullage
center of gravity
centro de gravedadThe 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.
On the test
Questions ask how a high center of gravity changes handling and why tankers and tall loads need slower curve speeds.
Appears in 28 test questions
See 11 questions on the Tanker testExample: With pallets stacked to the roof, you take the exit ramp well under the posted speed because the load sits high.
Diagram coming
Also called: high center of gravity
tank vehicle endorsement
endoso NThe 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.
On the test
Questions ask which vehicles need the tank endorsement and whether the liquid must be hazardous.
Differs by state: The capacity test is printed identically in every manual: an individual tank over 119 gallons and 1,000 gallons or more in total. Some manuals (GA, ME, PA, WY) still also print the pre-2011 rule, under which any permanently mounted cargo tank needed the endorsement. Legacy tables in ID, MI, VT and WV do the same. Most manuals attach N to Class A or B and add Class C only for hazmat loads. Arizona and California name Class A, B or C without that condition.
Example: Offered a job hauling liquid fertilizer, you add the N endorsement before your first run.
Also called: N endorsement, tanker endorsement
