07.05 How do you safeguard against overfills?

The primary safeguard against overfills is a properly sized gravity overflow pipe from the day tank and returning to the bulk storage tank. A secondary safeguard is a high level switch in the day tank that disables and closes the inlet control valve.

The primary safeguard of gravity overflow cannot be used where the bulk tank is at a higher elevation than the day tank, or where pipe routing considerations do not allow for gravity flow back to the bulk tank. In these circumstances, a return flow / overflow pump is needed along with additional protection.

The return flow pump is configured as either (a) a separate overflow receiving tank with pump out, or (b) a return flow pump mounted on each day tank. In either case the return flow pump should be sized for 125-150% capacity of the fuel supply to the day tanks.

Additional protection can be provided by a high level stop valve in the day tank inlet piping. This is typically a normally open solenoid valve that closes when a high level sensor is activated.