Which of the following is not an overfill prevention device?

• A. ball float
• B. spill bucket
• C. tank overfill alarm
• D. drop tube flapper valve

Answer: (B)

The correct answer identifies the spill bucket as not being an overfill prevention device. A spill bucket is designed to catch any excess liquid that may escape during tank filling or if there is a leak. It serves more as a secondary containment mechanism to prevent spills from reaching the environment rather than actively preventing overfilling of the tank itself.

In contrast, a ball float, tank overfill alarm, and drop tube flapper valve are all mechanisms specifically designed to prevent overfilling. A ball float works by rising with the liquid level and shutting off the flow when it reaches a certain height, the tank overfill alarm alerts personnel when liquid levels approach the tank's capacity, and the drop tube flapper valve closes off the flow once the tank is full to prevent overflow. These devices focus on controlling the liquid level in the tank during filling operations directly, making them essential components of overfill prevention systems.