Driving a liquid tanker is not dangerous, but it does require some advanced skills. Since the cargo is always moving, the driver needs to keep a few steps in front of the load, anticipating and keeping this movement in mind. Inexperienced tank drivers will run into trouble when they relax their vigilance and accidents occur.
In other words, driving the liquid tank is very satisfactory. It will naturally make you a better driver. You must always pay attention to how the liquid in the trailer reacts to any operation. From braking too hard or starting too fast, or driving too fast when turning, the liquid load is very ruthless.
There are dozens of types of liquid tankers. They are usually designed for specific types of goods. There are storage tanks designed for the transportation of chemicals, food-grade products, dairy products, gasoline, diesel and light fuel oil, storage tanks for the transportation of corrosive materials such as acids, and storage tanks for the transportation of extremely hot products such as liquid asphalt. Storage tanks, and storage tanks used to transport extremely cold products such as liquid oxygen. Liquid hydrogen.
Most commercial tanker fleets use mixing equipment, which usually includes general chemical and food grade tanks. The fuel tank barrels on these trailers are often made of different grades of stainless steel, and they rarely have any internal baffles to minimize or prevent terrible surges. These storage tanks have no baffles, so they can be cleaned thoroughly and efficiently before each load. The baffle also increases the weight of the trailer.
The size of most general chemical storage tanks can hold a variety of goods. The capacity of a general fuel tank for US service is usually about 6,000 gallons (22,700 liters). The number of gallons transported depends on the specific gravity or density of the liquid. For example, water weighs 8.3 pounds per US gallon. If you put 6,000 gallons of water into a tank, its weight will reach 49,800 pounds. With such a load, you are likely to be overweight.
On the other hand, sulfuric acid weighs close to 16 pounds per gallon. So in theory, you can only fill up the fuel tank by half or less before reaching the total weight limit in the United States. On the lighter side, some solvents (such as naphtha or commercial alcohol) can be as light as 6.5 pounds per gallon. You need a fuel tank larger than 6,000 gallons to get a full load.
In Canada, general chemical tank trailers tend to be larger—about 9,000 gallons (34,000 liters)—to carry more payload, but the same idea applies. You can load fewer heavier goods and more lighter materials. For drivers, towing a half-full trailer, heavy products like acid can be a very challenging journey. Not only do you have the most suitable volume for heavy surges (half full), but you also have a lot of products sloshing in the tank.
Most commercial tanker fleets use mixing equipment, which usually includes general chemical and food grade tanks.
Food-grade water tanks are usually made of finer stainless steel to facilitate proper cleaning. As long as proper cleaning procedures are followed, some edible products can be hauled in stainless steel chemical tanks. But the drain valve fittings are often different, and the food-grade fittings are designed to be easier to disassemble for thorough cleaning. Tanks designed to transport dairy products are also stainless steel. They have accessories designed specifically for the dairy industry.
Most chemical and food-grade storage tanks are insulated to keep the product warm. Many products (such as wax or chocolate) are loaded at 150-200 degrees Fahrenheit (65-95 degrees Celsius) to help them flow better during loading and unloading. If they cool down during transportation, the steam coil located under the barrel will reheat the product during unloading.
Chemical and food grade storage tanks are almost always cleaned between loads in commercial storage tank cleaning facilities. They have different cleaning chemicals and procedures to remove various cargo residues. The driver is not responsible for the actual cleaning of the fuel tank, but they need to inspect it before leaving the cleaning rack for reloading. The carrier provides training on how to inspect the trailer. In most cases, the customer will check the tank again before loading.
However, sometimes through inspection to play some small games. If the cargo is not ready when the truck arrives, the customer sometimes refuses the trailer and sends it back to the washing rack for rewashing instead of paying demurrage for the cargo that is not ready at the specified loading time.
Many types of fuel tanks are designed to transport specific products, such as the B-train you see transporting fuel to gas stations. Unless special items are hauled, these tanks are rarely washed out between loads. It is not a problem to load gasoline into the compartment that previously contained diesel, because there is hardly anything in the tank after unloading.
This type of fuel tank has several compartments, so they can be mixed with ordinary and high-quality gasoline and diesel. For these types of trailers, the compartments are almost always almost full, so there is no need to worry about surges, but their center of gravity is high and you need to be extra careful when turning and manoeuvring.
Storage tanks designed to transport acids and corrosive products have a small capacity because these products are heavy. A typical acid trailer used for service in the United States might have a capacity of 3,000 gallons (11,300 liters) because that is all the weight of the product they can carry.
Hot oil tanks and asphalt tanks are usually made of steel or aluminum. They are insulated and can hold products up to 350-450 degrees Fahrenheit (175-230 degrees Celsius). Unless they need to be repaired, they will hardly be cleaned up.
Tank drivers have much more plates than dry truck drivers. First, they must be familiar with the equipment, how it works, and how to check it. Cargo oil tanks have various safety functions that drivers need to know, such as pressure relief valves, internal and external discharge valves. The driver needs to know how to quickly close the valve in the event of an overflow or accident during loading and unloading.
The driver must be familiar with various unloading methods, there are several. If the customer uses his own pump to unload the cargo, the driver only needs to connect the discharge hose and then open the hatch on the top of the fuel tank to allow air to enter when the liquid is emptied. Otherwise, a vacuum will be formed in the tank and the tank will collapse.
Many tractors are equipped with a liquid pump so the driver can pump down the load. This involves the hose from the trailer to the pump and from the pump to the customer's tank. Some training is needed here because improper use of equipment can lead to overflows, customer dissatisfaction, and possibly environmental consequences.
Some storage tanks—especially acidic and corrosive tanks—use air pressure to unload. There is no bottom drain valve on this tank to reduce the possibility of leakage or accidental discharge. Instead, the hose is connected to the pipeline coming out of the top of the tank, but connected internally to the bottom of the tank. When the air pressure in the tank rises, the product is pushed up the discharge pipe and flows to the customer's storage tank. Monitor the pressure carefully to avoid opening the pressure relief valve.
Then there is gravity, just like a gasoline transport truck. The hose is connected to the truck and the underground storage tank, and the product flows downhill from the truck to the storage tank. The driver should ensure that there is enough space in the fuel tank to accommodate the quantity of product delivered.
Most gas stations still use a dipstick and tank calibration chart to determine how much space there is in the tank. Many modern storage tank facilities now use internal sensors instead of dipsticks or eyeballs to measure liquid levels.
Loading the fuel tank is not that complicated, but drivers still need to know exactly what they are doing. Most chemical and food-grade storage tanks are loaded from the top through open hatches. The pipe or hose is dropped and the product starts to flow. Some facilities use their own loaders; some rely on drivers to complete their work.
In some cases, the driver is responsible for dipping the tank to ensure that the correct amount of product is loaded. For example, if the driver were to pack 4,500 gallons into a 6,000 gallon tank, the calibration chart for that tank would show that the liquid level should be 12 inches from the top of the tank. When the liquid level reaches this mark, the drive stops the flow of product into the tank.
Tanks are also often loaded by weight, so the driver must calculate how many gallons per gallon will constitute 45,000 pounds. There is not much room for fault tolerance. Too light, customers will be upset. Too heavy, the inspector of roadside scales will be unhappy.
The shipper will never be happy to have to remove excess product, because the product is generally considered to be contaminated and therefore cannot be pumped back to the storage tank. Instead, it enters the sewage tank, and the carrier usually needs to pay for the spoiled product.
Almost all oil tankers are bottom loaders. Self-sealing fittings connect the loading arm to the tanker truck. The driver uses the keyboard to enter the number of products to be loaded into a given compartment, and then presses the start button. Various electronic cross-checks ensure that the vent on the top of the tank is open to prevent pressure build-up and that the internal drain valve is open to allow product to flow into the compartment.
For safety reasons, the top loading of oil tanks was cancelled a few years ago, but certain commodities are still used occasionally.
Some chemical products require additional safety procedures and precautions to prevent fumes from escaping into the atmosphere. For example, some products react with oxygen in the air, so they are loaded into a closed circuit, filling the voids in the tank with nitrogen. In this case, the loading and unloading are handled by experts, but the driver must be familiar with the special handling requirements to prevent emergencies during transportation.
As one might imagine, a large number of product-specific handling procedures are involved, and in many cases, specific personal protective equipment is required. Tank truck drivers need to understand the equipment, products, rules and regulations related to the transportation of dangerous goods or food handling requirements.
The annual income of tank truck drivers is often higher than that of truck and refrigerated truck drivers. Normally, mileage rates are no different, but tank drivers will see compensation for more non-driving activities, such as loading, unloading, and checking equipment.
It takes several hours to load a typical chemical or food-grade tank trailer, but it may require additional waiting time for equipment inspection and laboratory approval before shipping or receiving the goods. That time is usually paid by the hour, or at a flat rate that covers that time.
Tank drivers usually pay hourly wages from the beginning to the end of the shift, although some long-distance transportation services may also earn miles.
Due to the nature of certain goods, safety is ubiquitous in the field of tank trucks. If you don't like working in a highly structured environment, this may not be for you. Although dynamic loads, dangerous goods, and sometimes complex product handling requirements bring higher risks, the tanker industry has one of the safest records in truck transportation.
As I suggested before, hauling liquid tanks will force you to be a better and smarter driver. There is almost no room for error when cornering or failing to consider the risks posed by liquid gushing from the tank. You either drive a truck or drive a truck. The latter usually does not end well.
Tank truck drivers took the lead in adopting this technology long before the progressive shifting technology was considered a fuel-saving technology. The slow and easy upward movement of the gear can prevent the liquid from surging back and forth violently. When you accelerate, the liquid flows to the rear of the fuel tank, where it accumulates to critical mass, and then surges forward. Repeat this process until the truck reaches a steady speed and the liquid settles down.
When using a manual gearbox to upshift, the driver will go from first to second, second to third, and then stop and wait for the liquid to surge forward. At that time they would slide into fifth gear to take advantage of the momentum of the liquid. Good tank drivers will quickly figure out how to manage different types of liquids (rich or thin) and half or three-quarters full tanks. Their behavior is different.
Stopping can be trickier. When braking, the load impacts forward. Gentle braking produces gentle surges. Sudden braking will cause a heavy blow in the back, which will make your teeth rattle. Therefore, a good tank driver will predict the stop earlier and start to slow down. Generally gentle continuous braking applications are smoother than downshifts through gears. This only perpetuates more movement of the liquid.
Perhaps the worst-case scenario is hard parking on slippery roads. After the truck has stopped, the surging liquid will usually push the truck forward, possibly entering an intersection or over the top of the car parked in front of the truck. On a slippery road, 20 or 30 tons of fluid in motion cannot be compared with dozens of tires.
Perhaps the worst-case scenario is hard parking on slippery roads. After the truck stops, the surging liquid will often push the truck forward.
For the same reasons as above, driving up or downhill is challenging. If you downshift while climbing a hill, the change in momentum will cause the liquid to surge forward and then backward and may cause you to miss the downshift. Braking downhill causes the load to rush forward, which actually pushes the truck forward when you try to slow down. This is not good for your brakes. A good tank driver will slow down before starting to descend, choose a gear, depress the engine brake, and use the service brake carefully or not at all to prevent fluid surges.
And, of course, the liquid will rush to the side when turning, throwing more weight outward in the opposite direction of the turn. This obviously poses a risk of overturning. Drivers who turn too fast are at increased risk of overturning—especially in a high-tank trailer that is only partially full.
Nowadays, it is difficult to find a driver for tank trucks, more difficult than trucks and refrigerated trucks. The tanker industry has high requirements for "qualified drivers". They don't want cowboys and adventurers, and they are very reluctant to hire novice drivers.
If you are looking for a challenge and a job that keeps you alert, you might consider driving a tank. I have been driving on the road for 20 years, of which more than 15 years have been opening chemical tanks. I can honestly say that if I return to the driving field, I will find a job in tank driving.
From 1978 to 1998, Jim Park was a CDL driver and owner-operator, when he started his second career as a trucking journalist. During that career transition, he hosted an evening radio show on Radio Hamilton, Ontario, and later continued to host trucking news on SiriusXM’s Road Dog Trucking channel. Jim is a regular contributor to Today's Trucking and Trucknews.com and produces Focus On and On the Spot test drive videos.
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