Why Do Tanker Trucks Have Chains Hanging at the Back?

Electrical Technology

Why are Metal Chain Dragged by Petrol, Oil, and Fuel Trucks?

You may have noticed gasoline trucks trailing a metal chain or discharge strips. While they may not look appealing, they serve an important role in ensuring safety and protection. Tanker trucks often have chains hanging from the back to mitigate electrostatic discharge (ESD).

These metal chains are dragged by petrol, oil, and fuel trucks to safely dissipate static electricity that builds up on the truck’s body due to friction with the road. This helps prevent potential sparks that could ignite flammable fuel vapors during loading or unloading. Essentially, the chains act as a grounding mechanism, neutralizing the electrical charge by transferring it safely to the ground.

The following are the reasons for the dangling chain behind gasoline transport trucks carrying explosive materials.

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Preventing Electrostatic Buildup

Tanker trucks, especially those carrying flammable liquids like gasoline or diesel, can accumulate static electricity as they move. This buildup is caused by friction between the liquid and the walls of the tank, as well as between the tires and the road surface.

Grounding the Tanker

The hanging chains are designed to maintain contact with the ground and vehicle chassis as the truck moves. By doing so, they help dissipate static electricity safely into the earth, reducing the risk of sparks.

Preventing Fires or Explosions

Sparks from static discharge could ignite the vapors around flammable liquids, leading to dangerous fires or explosions. The chains act as a simple and effective safety measure to avoid such incidents.

Enhancing Safety During Loading/Unloading

During loading or unloading, the risk of static discharge is higher due to the movement of liquid. While grounding cables are typically used during these operations, the metallic chain provides an additional layer of safety.

Why Not Always Chains?

Recent research has concluded that chains are not essential to prevent the combustion of fuel tanks. As a result, they are no longer required by regulations. Instead, modern tanker trucks often use static discharge strips or conductive tires as effective alternatives to hanging chains, particularly when transporting hazardous materials.

What about the Sparks Made by Chains?

But don’t you think sparks from the metal chain hitting the tarmac could ignite any leaked flammable material

Not at all. The chain doesn’t strike the road with enough force to cause sparks. It swings gently and touches the tarmac intermittently with minimal pressure.