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Understanding over/under
Even with real time corrections from the self-correcting network, an occasional overweight reading still happens. API drift and temperature are the two real causes, and both are explainable, not random.
Here's why each one happens, and exactly what to do if your load report shows you over the legal limit.
Why you might go overAPI drift is the most common cause, and the hardest to predict. When a terminal receives a new shipment, the product gravity will shift. The change is usually minor and equates to less than a couple hundred pounds in a full load. Setting the target slightly lower than legal will accommodate these minor swings.
However, there have been black swan events in which a dramatically heavier product is received, likely a different grade from an atypical refinery. This is an outlier, but traditionally every driver would need to load significantly less than they otherwise could, all the time, just to accommodate the worst case scenario. ProTankr attempts to remedy this. The first driver to observe the drift records it, correcting the density calculation for everyone thereafter. The "as of" date shown next to the planned API in your load report tells you how stale the API reading is. A reading from four days ago is a warning sign. In this case, simply load light or update the API from a more current BOL before loading.
The silver lining: the moment you enter the actual API from the BOL at the loading rack, two things happen. You will know immediately, before crossing any scale, if the load is overweight, and will have a chance to correct it, virtually eliminating any overweight tickets. The app is updated for that specific product at that terminal for every driver who loads there next. The next driver plans with your fresh observation, and the community self-corrects in real time.
Temperature is the second cause. If the product is cooler than planned it is denser, meaning more product is condensed into the same gross gallon. The pump only recognizes volume, so more product ends up on board. The temperature prediction model attempts to remedy this variable. The model has a self-training feature that over time will dial the prediction closer and closer to reality with every load. Still, there are unknown variables that cannot be fully accounted for in any model.
However, there have been black swan events in which a dramatically heavier product is received, likely a different grade from an atypical refinery. This is an outlier, but traditionally every driver would need to load significantly less than they otherwise could, all the time, just to accommodate the worst case scenario. ProTankr attempts to remedy this. The first driver to observe the drift records it, correcting the density calculation for everyone thereafter. The "as of" date shown next to the planned API in your load report tells you how stale the API reading is. A reading from four days ago is a warning sign. In this case, simply load light or update the API from a more current BOL before loading.
The silver lining: the moment you enter the actual API from the BOL at the loading rack, two things happen. You will know immediately, before crossing any scale, if the load is overweight, and will have a chance to correct it, virtually eliminating any overweight tickets. The app is updated for that specific product at that terminal for every driver who loads there next. The next driver plans with your fresh observation, and the community self-corrects in real time.
Temperature is the second cause. If the product is cooler than planned it is denser, meaning more product is condensed into the same gross gallon. The pump only recognizes volume, so more product ends up on board. The temperature prediction model attempts to remedy this variable. The model has a self-training feature that over time will dial the prediction closer and closer to reality with every load. Still, there are unknown variables that cannot be fully accounted for in any model.
Drain-down calculationIf the load report shows you are over the legal 80,000 lb gross limit, it will calculate exactly how many gallons to drain from the rear compartment to bring you legal. This uses the actual observed density from that compartment's loaded weight and gallons.
Be sure to follow company policy to account for where and how to drain-down, if ever necessary. This is only meant to quickly determine the exact gallons required to get legal again. Keep in mind the burn buffer from the saddle tank(s) could make any drain-down unnecessary. If the tare weight entered included a full saddle, you will have burned roughly 25 gallons by the time you reach the scale, so if the calculated drain-down is less than 25 gallons, you're in good shape.
Be sure to follow company policy to account for where and how to drain-down, if ever necessary. This is only meant to quickly determine the exact gallons required to get legal again. Keep in mind the burn buffer from the saddle tank(s) could make any drain-down unnecessary. If the tare weight entered included a full saddle, you will have burned roughly 25 gallons by the time you reach the scale, so if the calculated drain-down is less than 25 gallons, you're in good shape.
Self-Correcting Network