Shut-off devices intended for use with USTs are suitable for which type of deliveries?

Shut-off devices for underground storage tanks (USTs) are specifically designed to prevent the overfilling of tanks during fuel deliveries. These devices are essential for ensuring safety and compliance with environmental regulations. They automatically shut off the flow of fuel when the tank reaches its capacity, reducing the risk of spills and potential hazards.

Focusing on the correct answer, shut-off devices are particularly suited for gravity deliveries. In gravity delivery systems, fuel is delivered by allowing it to flow from a higher elevation into the UST, which can present challenges in controlling the flow precisely. The shut-off device ensures that even in these scenarios, the tank does not exceed its safe volume, preventing overfilling.

In contrast, the other types of deliveries such as unmanned or quick deliveries rely on different methods of control and may employ additional safety measures and monitoring systems. While shut-off devices may enhance safety in all types of deliveries, they are specifically regarded as crucial for gravity systems due to the inherent risk of uncontrolled overflow in this method.

Thus, gravity deliveries represent the most critical scenario where the functionality of shut-off devices is indispensable, emphasizing their role in maintaining safety standards and environmental protection in UST operations.