Shut-off devices designed for use with USTs should only be used with which type of deliveries?

Shut-off devices for underground storage tanks (USTs) are specifically designed to enhance safety during fuel deliveries by preventing spills and leaks in the event of a malfunction. These devices work effectively when employed with gravity deliveries, as this type of delivery relies on the natural gravity flow of the fuel without additional pressure. In gravity systems, managing the flow and ensuring that any leak or spill is contained is crucial, which is why shut-off devices are well-suited for these deliveries.

In the context of unmanned and quick deliveries, the operational dynamics differ. Unmanned deliveries may not have the immediate oversight required to respond quickly to issues that arise, and quick deliveries often involve a pump or pressure system that could potentially bypass the effectiveness of shut-off devices if not monitored closely. Hence, while safety measures are critical across all delivery types, the compatibility and effectiveness of shut-off devices are best associated with gravity deliveries due to their design and operation requirements.