The Loading and Unloading Process of Fuel Tank Trailers

Fuel tanker trailers are responsible for transporting billions of gallons of valuable, yet highly flammable petroleum products, such as gasoline, diesel, benzene, jet fuel, and compressed natural gas (CNG), across the globe. However, the hazardous nature of these products presents significant safety risks both on the road and during loading and unloading operations.

In the United States, the Department of Transportation mandates that all bulk petroleum transport vessels comply with the DOT 406 fuel tank regulations, which aim to ensure the safe transportation of flammable liquids. These regulations require that fuel tanker trailers meet specific design and construction standards and follow established protocols during loading and unloading. These apply to tank trailers transporting bulk fuel products such as gasoline, and diesel. In this article, we will be specifically talking about the loading and unloading process of a fuel trailer, and the established protocols for its safe loading and unloading by the US Department of Transportation. If you want to read more about the DOT 406 compliance regulations, read  here.

In this article:

  • Minimum requirements and regulations for tank trailer loading/unloading.

  • Things to keep in mind before, during, and after loading and unloading the fuel tank trailer?

  • Loading Process

  • Unloading Process

  • Safety Measures

  • Do’s and Don'ts while loading or unloading of a fuel tank trailer. 

Minimum requirements and regulations for tank trailer loading/unloading.

Attendance requirements during the loading and unloading

The minimum requirements are established by the U.S Department of Transportation for loading and unloading the fuel tank trailers to make the loading and unloading process safer and easier. These protocols include the requirement of a qualified attendant to manage the procedures while loading and unloading inflammable products into the tank trailer. 

  • The vessel must be attended by a qualified person at all times during its loading and unloading. 

  • As per the DOT regulations for fuel tank trailers, attendees must have a good understanding of the highly flammable products they are going to handle before they are permitted to attend.

  • The attendant always has to maintain a distance of 25 feet (7.62metres) from the tank trailers. This is a straight line distance; a walking distance, not a field of view.

  • The qualified person always needs to be alert for any type of unusual and potentially dangerous or difficult circumstances.

  • During the loading and unloading process, the attendant must have an unobstructed view of the tank trailer and hoses connected to the tank trailer.

Fuel Tanker Trailer Loading Process

A fuel tank trailer can be loaded either of the two ways, top loading or bottom loading. Both tank trailer loading methods have their own benefits and disadvantages, as discussed below.

Top Loading: Top loading was he most common fuel trailer loading method. Prior to the discovery of the bottom loading method, all types of fuels, such as gasoline, diesel, and jet-A fuel, were loaded using the top-loading method. However, this form of loading has a particular set of concerns, both in terms of safety and potential environmental damage. Loading fuels or other liquids from the top is unsafe and risky as the gasoline vapors get introduced into the station's atmosphere, which is highly flammable, ready to combust at a moment's notice. Furthermore, the evaporated liquid reduces the volume of the tank. This method is no longer recommended for flammable liquids, after the discovery of the bottom loading method.

  • Bottom loading:  Bottom loading process is one of the best & safest methods for loading highly flammable liquids like petroleum, diesel, and other fuels. In this method, fuel gets into the tank trailer from the bottom, which allows circulating the hazardous vapor within the internal circulation path of the tanker. As a result, the bottom loading method reduces the risk of explosion and is recommended for loading flammable liquids, making it a much safer, reliable, and faster method for loading products.

Unloading process of the fuel tank trailer

Before starting the process of unloading a fuel trailer, the driver ensures that the tanker trailer is parked in the proper unloading position and the truck's engine is turned off (unless required to operate a pump). Once the trailer is parked, the attendant inspects the area to ensure that nothing is out of place and ensure that the unloading equipment is in proper working condition. The attendant attaches the unloading hose after uncapping the discharge connection of the tank trailer to confirm all hoses are connected to the right tank. After that, a qualified personnel on-site must connect the vapor recovery system to control and prevent vapor release of the product or fuel at the site. The driver or the attendee, must inspect the connections and hoses for any indications of leaks.

They should be on constant check for any type of leaks, vent overfills and other potential issues during the unloading process. After the unloading is completed, they must check that all the product has been drained from the tank trailer and ensure turning off the valves. Lastly, the residual product is drained from the fittings and the hoses are placed at their designated places.

Equipment and systems used in loading and unloading

Loading and unloading flammable products are risky and complicated, which is why these procedures necessitate the use of various types of equipment and systems to facilitate the loading and unloading of these products. Loading and unloading equipment includes hoses, wires, pumps, as well as a vapor recovery system to ensure optimal safety while transferring bulk liquid. Each of these are the main equipment for the process because hoses are used to transfer the product from one tank to another, whereas wires are used to operate the pump and create suction for easy unloading the product. On the other hand, a vapor recovery system is one of the essential equipment in the process. A vapor recovery system is a set-up designed to remove harmful and unwanted vapor from the fuels and prevent them from causing build-ups in tanks. It also increases purity and prevents hazardous pollutants from entering the environment.

Safety Measures

Because these loading and unloading processes are dangerous and risky, you must adhere to all safety precautions such as Personal Protective Equipment (PPE) which includes body cover, face shield, gloves, and safety shoes, at all times when loading or unloading flammable liquids from the tank trailer.

Do’s and Don'ts while loading or unloading fuel tank trailers. 


  1. Incharge must be alert throughout the process

  2. Keep a clear view of the fuel tank trailer and delivery hose until the process is complete.

  3. The in-charge should be within 25 feet of the tank trailer.

  4. Should have a knowledge of the hazards of the product.

  5. Know the process to follow in an emergency.

  6. Be authorized to move the cargo tank and be able to do so.

  7. Close all manholes and valves before moving the tank trailer.

  8. Turn off the engine before loading or unloading flammable liquids. (Only run the engine if needed to operate a pump).

  9. Before the process begins, set the brake interlock valve on the tank trailer.


  1. No smoking or calling around the loading or unloading area.

  2. Do not light match for any purpose.

  3. Do not stand too close to the tank trailer during the process.

  4. Don’t use broken tools or equipment.

  5. Do not start the loading or unloading process without any qualified supervision.

  6. Don’t forget to close all the manholes of the fuel tank trailer after the procedure.

Things to keep in mind before, during, and after loading and unloading the fuel tank trailer.

As the procedure of loading and unloading the fuel tank trailer is crucial, everyone who is involved in the procedure must have to be alert while transferring the product. There are some tasks to be done and rules to follow before, during and after the loading and unloading process of the fuel trailer.

Prior to loading/unloading

Firstly, before unloading or loading the flammable liquids, the driver must apply the parking brakes and secure the tank trailer using wheel chocks and interlocks to ensure that the tank trailer does not move throughout the transferring process. Following that, the qualified attendee must visually inspect all hoses for leaks and wet spots, as well as ensure that there is sufficient volume in the storage tank or in the tank trailer. The qualified individual must also ensure that the valves are properly aligned and that the pumping system is operating properly. Finally, the driver and any personnel who are close to the tank trailer must turn off their cell phones. Before beginning the loading or unloading, the personnel must put on all of their safety equipment, including a hard hat or helmet, face shield, goggles, rubber suit, gloves, pants, and rubber boots. All of these protective gear are designed to minimize impact of the hazardous product to humans.

During loading/unloading

The driver must stay with the tank trailer during the loading or unloading process in order to tackle any type of emergency as quickly as possible. Personnel should inspect all systems, hoses, and pipe connections between the tank trailer and the storage tank during the transferring process, monitor the liquid level in the receiving tank on a regular basis to prevent product overflow, and also check the flow meter to assess the rate of flow of the liquid.

After loading/unloading

Once the transfer is complete, ensure all the tank and loading valves are closed before disconnecting and the hoses are drained to remove all the liquid before moving them away from the connection. After this, the driver or attendee must have to check and close all the internal or external domes and hatches. Now, the driver should have to remove the wheel chokes and interlocks to move the tank trailer.

The loading and unloading process of the fuel tank trailer is a simple task for those who are performing it on the regular basis, however, one must be alert and disciplined to perform these tasks as it can have grave consequences in case of a mistake. These generic processes include inspecting the tank trailer and equipment, ensuring the tankers are suitable for the product they are going to hold, opening and closing the valves accordingly, and lastly, some legally mandated paperwork before leaving the site. This highly sensitive process always requires an expert level of competence on the part of the driver and the attendant to pay attention throughout the entire loading and unloading process.