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CDL · Loading and Unloading

When loading or unloading a tank truck of flammable liquids, what is required?

Correct answer

Engine must be turned off during loading/unloading unless required to operate the pump, and the truck must be bonded and grounded to dissipate static electricity

  1. A Engine must be running to power the pump
  2. B Engine must be turned off during loading/unloading unless required to operate the pump, and the truck must be bonded and grounded to dissipate static electricity
  3. C Driver may leave the vehicle unattended
  4. D Smoking is permitted at the back of the truck

Why this is the answer

Loading and unloading flammable liquids — gasoline, jet fuel, ethanol, etc. — requires extreme care because vapors form an explosive mixture with air. The engine is turned off unless required to power the truck's loading pump. Bonding wires connect the truck to the loading rack, equalizing static electrical potential so static sparks cannot ignite vapors. Grounding wires connect the truck to earth ground for the same purpose. The driver must remain at the loading point throughout — never leave the truck unattended during a transfer. Smoking, open flames, and even cell phones with potentially spark-causing characteristics are prohibited within the regulated distance (typically 25 feet). A static spark in a vapor cloud has caused many catastrophic refinery and terminal fires.
Source: FMCSA CDL Manual 9.3.5 Loading Flammable Liquids

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