Two limits apply at the same time: the load must not put the vehicle over legal weight limits, and enough room must remain for the liquid to expand on the road. A driver has to account for both before filling the tank.
A liquid takes up more room as its temperature rises, so a cargo tank is never loaded to the very top. The unfilled space set aside for that expansion is what tanker drivers call outage.
Every liquid swells as its temperature rises, but not by the same amount. Knowing the outage each product needs lets you leave enough empty space for that growth, so the cargo does not spill out or put the tank under excess pressure.
Throughout the transfer, the responsible person must keep the tank in clear view from a distance of no more than 25 feet.
Inspections belong at every stage of the job: before the tank is filled, before it goes on the road, and before it is emptied. Each check confirms that the tank can hold its product safely and that the truck is fit to drive.
Liquids grow in volume as they warm, so some empty space, called outage, must be left for that expansion. A heavy, dense liquid can also push a full tank past legal weight limits, which is why such loads are often only partly filled.
These valves are opened only to load or unload the product. The rest of the time, whether the vehicle is moving or parked, they must stay shut.
Filling some compartments and not others, or filling them unevenly, can put too much weight on the front or rear of the vehicle and overload an axle. Plan the order of loading and unloading so the weight stays balanced.
Some liquids, such as certain acids, are heavy enough that a completely full tank can put the vehicle over the legal weight limit. The density of the product, not just the size of the tank, determines how much can be loaded.
With any tank, leaks are the top concern, so look under and around the vehicle for signs that something is escaping. A leaking tank must be fixed before it is used, because the escaping cargo can cause fires, spills or injuries, especially when it is a hazardous material.
Bulkheads split a tank into several smaller compartments, and emptying them in a careless order can leave too much weight over the front or the rear of the vehicle. Keep track of how the remaining load is spread out as each compartment is unloaded.
Leaks are the top concern on a tanker inspection, because it is illegal to haul cargo in a tank that you know is leaking.
Liquids grow in volume as they heat up, and each product does so at its own rate, known as its coefficient of expansion. A liquid that expands a lot needs more empty space left at the top of the tank than one that barely expands.
Because liquids expand when their temperature rises, a tank should never be loaded completely full; the unfilled space kept for that growth is called outage. The amount required varies from one liquid to another.
Before a tank vehicle is loaded, unloaded or driven, it needs to be inspected. The inspection tells you whether it is safe to operate and suitable for hauling liquid or gas cargo.
How much product goes into a tank depends on how much it will expand along the way, how heavy it is, and how much weight the law allows the vehicle to carry. Leaving too little room or loading too much weight can make the load unsafe or illegal.
Joints, the spots where one pipe is fastened to another, deserve the closest look, since connection points are a common place for leaks to start.
In a tank split into compartments by bulkheads, pay attention to how the weight is spread as each compartment is filled or emptied. Too much weight over the front or the rear upsets the balance, so most of it belongs in the middle.
Knowingly operating a leaking tanker is against the law. A driver caught doing it can be cited and kept from driving any farther.
Every manhole cover has to be shut before the trip so the tank stays sealed and its contents cannot leak out. Leaving one open, even slightly, can lead to spills or escaping vapors.
Every question in this set has its own page with the correct answer and an explanation.
