We do the same thing. We use switches to indicate if the valve door is open or closed and are developing a fully electronic lock that will need to satisfy a range of parameters for it to be opened. This will include a receiver iButton.
Dispensed fuel is captured using an in tank ATG on the ground tanks, up to 5,000,000 liters. We use a geozone alert to give us the delivery location entry and then poll the ATG for the filled volume for comparison back to truck load record. If the amount dispensed is less than the loaded volume an alert is produced. The ATG capture water levels as well as caries out leak tests
We also have flow meters on the trucks for in transit dispening to smaller tanks or to heavy equipment, but you have to develope a process to ensure that you do not suck air through the meter or the reading is inaccurate. This allows the capture of the dispensed volume, totalizer and temperature. We are in the process of adding density sensors at themoment.
For our barges we use a pressure based level sensor. That transmits levels for inventory calculation as well as volume change for comparison.
We are now looking at installing pressuer based sensors on the tanker trucker trucks to monitor intransit inventory.
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