What combination of overfill-prevention devices is commonly used?

The combination of overfill-prevention devices that is commonly used includes flow shut-off devices, alarms, and vent-restriction devices because this trio provides a comprehensive approach to preventing overfills in underground storage tank systems.

Flow shut-off devices are crucial as they automatically stop the flow of product into the tank when the liquid reaches a predetermined level, thereby directly preventing overfills. Alarms serve as a warning system, alerting operators to potential overfill situations before they occur, allowing for immediate corrective action. Vent-restriction devices are important for managing the pressure in the tank and ensuring that vapors do not escape excessively, which could lead to tank failure or other environmental hazards.

This combination of devices ensures that there are multiple layers of protection against overfilling, making it a common and effective approach in the industry for maintaining safety and compliance with regulations.