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Describe unbaffled liquid tankers:
Tankers often have Intake, discharge and cut-off valves. What should you check before loading, unloading, or moving the vehicle?
What have tests shown about tankers, and how should you manage it?
On all tank vehicles, the most important item to check for is:
High center of gravity means:
What should you do if you're pulling a tanker and you find a small leak?
Liquid surge results from the movement of the liquid in partially filled tanks. What are some characteristics of liquid surge?
A Tank Vehicle endorsement is required if your vehicle needs a Class A or B CDL and you want to haul a liquid or liquid gaseous material in individual permanently mounted cargo tank(s) rated in excess of:
When can you drive a tanker with open valves or manhole covers?
What are some methods for controlling surge in a tanker?
Keep a steady pressure on the brakes. Do not release too soon when coming to a stop. Brake far in advance of a stop and increase your following distance.
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The The Tank Vehicles written CDL Exam is required to obtain your tanker vehicle endorsement on your CDL. A tank endorsement is required for certain vehicles that transport liquids or gases. The liquid or gas does not have to be a hazardous material.
A tank endorsement is required if your vehicle needs a Class A or B CDL and you want to haul a liquid or liquid gaseous material in individual permanently mounted cargo tank(s) rated in excess of 119 gallons with an accumulating total rated at 1000 gallons or more or a attached portable tank rated in excess of 1,000 gallons.
This section will cover:
Tank vehicles have special items that you need to check. Tank vehicles come in many types and sizes. Check the vehicle's operator manual to make sure you know how to inspect your tank vehicle.
On all tank vehicles, the most important item to check for is leaks. Check under and around the vehicle for signs of any leaking. Do not carry liquids or gases in a leaking tank. To do so is a crime. You will be cited and prevented from driving further. You may also be liable for the clean up of any spill. In general, check the following:
High center of gravity means that much of the load's weight is carried high up off the road. This makes the vehicle top-heavy and easy to roll over. Liquid tankers are especially easy to roll over. Tests have shown that tankers can turn over at the speed limits posted for curves. Take highway curves and on ramp/off ramp curves well below the posted speeds.
Liquid surge results from movement of the liquid in partially filled tanks. This movement can have bad effects on handling. For example, when coming to a stop, the liquid will surge back and forth. When the wave hits the end of the tank, it tends to push the truck in the direction the wave is moving. If the truck is on a slippery surface such as ice, the wave can shove a stopped truck out into an intersection. The driver of a liquid tanker must be very familiar with the handling of the vehicle.
Some liquid tanks are divided into several smaller tanks by bulkheads. When loading and unloading the smaller tanks, the driver must pay attention to weight distribution. Do not put too much weight on the front or rear of the vehicle.
Baffled liquid tanks have bulkheads in them with holes that let the liquid flow through. The baffles help to control the forward and backward liquid surge. Side-to-side surge can still occur. This can cause a roll over.
Unbaffled liquid tankers (sometimes called "smooth bore" tanks) have nothing inside to slow down the flow of the liquid. Therefore, forward-and-back surge is very strong. Unbaffled tanks are usually those that transport food products (e.g., milk). (Sanitation regulations forbid the use of baffles because of the difficulty in cleaning the inside of the tank.) Be extremely cautious (slow and careful) in driving smooth bore tanks, especially when starting and stopping.
Never load a cargo tank totally full. Liquids expand as they warm and you must leave room for the expanding liquid. This is called "outage." Since different liquids expand by different amounts, they require different amounts of outage. You must know the outage requirement when hauling liquids in bulk.
A full tank of dense liquid (such as some acids) may exceed legal weight limits. For that reason, you may often only partially fill tanks with heavy liquids. The amount of liquid to load into a tank depends on:
Because of the high center of gravity and the surge of the liquid, you must start, slow down and stop very smoothly. Also, make smooth turns and lane changes.
Keep a steady pressure on the brakes. Do not release too soon when coming to a stop. Brake far in advance of a stop and increase your following distance. If you must make a quick stop to avoid a crash, use controlled or stab braking. Also, remember that if you steer quickly while braking, your vehicle may roll over.
Slow down before curves, then accelerate slightly through the curve. The posted speed for a curve may be too fast for a tank vehicle.
Keep in mind how much space you need to stop your vehicle. Remember that wet roads double the normal stopping distance. Empty tank vehicles may take longer to stop than full ones.
Do not over steer, over accelerate or over brake. If you do, your vehicle may skid. On tank trailers, if your drive wheels or trailer wheels begin to skid, your vehicle may jackknife. When any vehicle starts to skid, you must take action to restore traction to the wheels.