Mixed Deck — All CDL TANK Topics Flashcards

A DOT-specification cargo tank must have an external visual inspection and leakage test at least how often?

Answer: Every year

Under 49 CFR 180.407, DOT-specification cargo tanks need an external visual inspection and leakage test at least once each year. The longer 5-year interval applies to pressure retests, not to these checks.

Compared with a smooth bore tank, what is the main handling advantage of a baffled tank?

Answer: Less front-to-back liquid surge when braking or accelerating

Baffles have holes that slow liquid moving through the tank. This reduces front-to-back surge compared with a smooth bore tank.

A baffled tank still has what remaining surge concern?

Answer: Liquid can still move side to side, which can contribute to a rollover

Baffles slow forward-and-back movement, but liquid can still move side to side. That sideways movement can contribute to rollovers.

Compared with the same truck carrying a full load, an empty tank truck generally:

Answer: Needs a longer distance to stop because it has less traction

Empty trucks take longer to stop than loaded ones because a lighter vehicle has less traction. Brakes designed for heavy loads can lock up or skid more easily when the truck is empty.

Why does a smooth bore tank call for especially gentle braking and acceleration?

Answer: The liquid can surge freely from end to end, which can push the vehicle

With no internal barriers, the liquid moves freely and its momentum can push the truck forward or back.

A tank vehicle is carrying a partially filled load. What is "liquid surge"?

Answer: Movement of the liquid back and forth or side to side inside the tank

Liquid surge is the movement of liquid in a partly filled tank, forward and backward or side to side. It happens when the vehicle accelerates, brakes, or turns.

When can a driver leave a cargo tank unattended during loading or unloading of a regulated product?

Answer: Never, a qualified person must stay attending and watch the tank

Federal rules require a qualified person to attend the cargo tank during loading and unloading, staying within a short distance with a clear view of it. The attendant must be able to act fast.

Which technique is best for slowing a tank truck that is carrying a partial load?

Answer: Brake early and smoothly, and allow extra following distance

Braking early and smoothly, with extra following distance, keeps liquid surge to a minimum. It also gives the driver room to control the truck.

What is the main purpose of baffles inside a tank?

Answer: To slow the liquid's forward-and-back surge

Baffles are walls with holes in them. They let liquid pass through but slow its forward-and-back movement.

A driver is hauling a tank that is only half full of liquid. What happens to the liquid when the driver brakes, and how should the driver brake?

Answer: The liquid surges forward, so the driver should brake early and gradually

Liquid in a partly filled tank moves forward when the truck brakes, and the surge pushes the truck ahead. The driver should brake early and gradually to keep it under control.

What is the main reason a compartmented (bulkheaded) tank reduces surge?

Answer: Each compartment is a separate tank, so the liquid cannot surge along the whole length

Bulkheads divide the tank completely, so each compartment acts as a separate tank. Liquid can only surge within its own compartment.

You haul a very dense liquid, such as some acids. Why are such loads often carried in a tank that is only partly full?

Answer: A full tank of a dense liquid could exceed legal weight limits

A dense liquid weighs more per gallon, so a full tank can be overweight. Partial loads are common, which means surge must be managed even though the tank is not full.

Why is a smooth bore tank especially hard to drive when it is only partly full?

Answer: The liquid has room to build up a large surge from end to end

A partly full smooth bore tank gives the liquid room to move over a long distance and build up a strong surge. Nothing inside stops it.

A driver hauls several portable tanks on a flatbed. Each tank has a rated capacity of 100 gallons, and together they hold 1,200 gallons. Under the federal definition, is this a tank vehicle?

Answer: No, because no individual tank is rated over 119 gallons

Both conditions must be met. Each tank must be rated over 119 gallons and the aggregate must be 1,000 gallons or more. Here the individual tanks are only 100 gallons.

A driver of a tank vehicle on a slippery road must stop at an intersection ahead. Which approach reduces the risk caused by liquid surge?

Answer: Brake early and gently, and leave extra room to stop

Braking early and gently reduces the strength of the surge and gives more room to stop. Hard braking sends a large wave of liquid forward, which can push the vehicle into the intersection.

Why is it still important to drive carefully when a tank vehicle is empty?

Answer: Residue and vapors can remain in the tank and may still be dangerous

An empty tank that carried hazardous liquids or flammable materials can still contain residue and vapors. It must be handled as if it were loaded.

Compared with a light liquid, a dense liquid in the same partly filled tank, moving at the same speed, will generally:

Answer: Carry more momentum, so its surge pushes harder on the vehicle

Momentum depends on mass. The same volume of a denser liquid has more mass and delivers a stronger push when it surges.

Product begins leaking from a hose connection while you are unloading a cargo tank. What should you do first?

Answer: Activate the emergency shutoff or stop the flow of product

Stopping the flow, using the emergency shutoff if needed, limits the amount released. Driving away or waiting makes the spill worse.

On the test markings of a DOT-specification cargo tank, what does the letter "P" indicate?

Answer: Pressure test

"P" marks the pressure test. The markings record which test was done and when.

A driver is loading a tank with several separate compartments. What is true of the surge in a bulkhead-divided tank?

Answer: Surge is limited to the liquid within each compartment

Bulkheads are solid, so each compartment acts as its own tank. Liquid can surge only within its own compartment.