What must be done before unloading most cargo tanks carrying Class 3 (Flammable Liquids)?

Grounding cargo tanks that carry Class 3 (Flammable Liquids) is essential because it helps prevent the buildup of static electricity, which can ignite these flammable materials. When flammable liquids are being transferred from a tank to another container, static discharge is a significant risk. If the tank is not properly grounded, any static electricity that accumulates can create a spark, leading to a fire or explosion. Therefore, establishing a safe grounding connection ensures that any static charge is safely discharged to the ground before unloading, thus minimizing the risk of ignition from static electricity during the transfer process.

While inspecting for leaks is crucial for safety, and closing valves is important for operational integrity, neither of these actions specifically addresses the hazard posed by static electricity, which is paramount when dealing with flammable liquids. Heating flammable liquids is also not a standard safety practice before unloading and could increase the risk of fire or explosion.