California Designated Operator Practice Exam

Which of the following systems prevents overfilling of tanks by alerting operators at 90% capacity?

1. A ball float valve

2. A manual shut-off valve

3. A pressure release valve

4. An emergency venting system

The correct answer is: A ball float valve

The ball float valve is designed to prevent overfilling of tanks by using a buoyant float that rises with the liquid level. As the liquid in the tank reaches a specific level, typically set at 90% of the tank's capacity, the float will lift and close the valve, effectively stopping any further flow into the tank. This mechanism is crucial for managing liquid levels and ensuring that tanks do not exceed their safe capacity, thereby reducing the risk of spills and enhancing safety. In contrast, the other options serve different purposes. A manual shut-off valve is operated by personnel and does not automatically respond to liquid levels. This means it might not provide the timely alerts needed to prevent overfilling. A pressure release valve is designed to relieve excess pressure in a system, which is crucial for safety against pressure build-up, but it doesn’t specifically monitor tank capacity. An emergency venting system allows gases to escape in case of excessive pressure but does not actively monitor or manage liquid levels in the tank. Thus, the ball float valve is the most appropriate system for alerting operators when a tank reaches 90% capacity, making it essential for preventing overfills and maintaining safety protocols in tank management.