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.

You are watching: How are bulkheads different than baffles

Bulkheads:

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 tanks:

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 tanks:

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.

How Much to Load
*

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 often may only partially fill tanks with heavy liquids. The amount of liquid to load into a tank depends on:


The amount the liquid will expand in transit.The weight of the liquid.Legal weight limits.

8.3 Safe Driving Rules

To drive tank vehicles safely, you must follow all safe driving rules:

Drive smoothly - 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.Braking - If you must make a quick stop to avoid an accident, use controlled or stab braking. If you do not remember how to stop using these methods, review Section 2.13. Also, remember that if you steer quickly while braking, your vehicle may roll over.Curves - Slow down before curves, then accelerate slightly through the curve. The posted speed for a curve may be too fast for a tank vehicle.Stopping distance - 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.Skids - 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.

Test Your Knowledge

How are bulkheads different than baffles?Should a tank vehicle take curves, on-ramps, or off-ramps at the posted speed limits?How are smooth bore tankers different to drive than those with baffles?What three things determine how much liquid you can load?What is outage?What is the minimum tread depth for front tires?For other tires?

Study section 8.2 if you can"t answer all of these questions.


Baffle:

A partition or separator within a liquid tank, used to inhibit the flow of fluids within the tank. During acceleration, turning, and braking, a large liquid-filled tank may produce unexpected forces on the vehicle due to the inertia of liquids.

Bulkhead:

A strong wall-like structure placed at the front of a flatbed trailer (or on the rear of the tractor) used to protect the driver against shifting cargo during a front-end collision. May also refer to any separator within a dry or liquid trailer (also called a baffle for liquid trailers) used to partition the load.

See more: Penalty For Knocking Over A Hurdle Rules, Should There Be Penalties For Hitting Hurdles

HOS:

Hours Of Service

HOS refers to the logbook hours of service regulations.
*

In order to drive tank vehicles safely, remember:

Drive smoothly - 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.Braking - If you must make a quick stop to avoid an accident, use controlled or stab braking. Also, remember that if you steer quickly while braking, your vehicle may roll over. Curves - Slow down before curves, then accelerate slightly through the curve. The posted speed for a curve may be too fast for a tank vehicle.Stopping distance - 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.Skids - 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.