REFILL VOLUME
This is the amount of asphalt you can add to a tank that is partially filled. It is the difference between the net volume (Figure 2) and the volume currently in the tank. It is also an indication of how many gallons have been used since the tank was last filled. But this assumes that the net volume is accurate as discussed earlier. Moreover, it assumes that you are not actually using asphalt from the tank while it is being refilled.

The best way to verify how many gallons a supply truck has added to refill your tank is to record radar levels or gauge levels before and after refilling. Then convert the two levels to gallons according to Figure 3. The difference between the two indicates how much the supply truck added. Again, you cannot make an accurate determination if you are using asphalt from the tank at the same time it is being filled.

ACCURACY
Certain errors are unavoidable when measuring levels and converting them to gallons of asphalt stored in the tank or the number of gallons used. Such determinations are not reliable substitutes for metering and calibration equipment.

Several factors affect the accuracy of determining exactly how many gallons of asphalt are in your tank. One factor is the amount of error in the level measurement. Another is the manufacturing tolerances related to the diameter of the tank.

Level measurements can be made any of three ways: radar sensor, gauge board, measuring tape. These measurements sometimes have errors up to an inch. One inch of level equals 58.8 gallons. So the number of gallons could be off that much due to measuring errors.

The actual diameter of your tank may vary from its design diameter due to manufacturing tolerances. Vertical tanks are currently designed with an inside diameter of 131.5 inches. This is the diameter used to calculate the gallons shown in Figure 5. Variances in diameter due to normal manufacturing tolerances may cause the actual number of gallons to differ slightly from the number of gallons shown in Figure 5 for a specific level .

In the past not all Heatec vertical tanks were designed with a diameter of 131.5 inches. If your tank was designed with a different inside diameter, you should not attempt to use Figure 5. The gallons shown in Figure 5 will be significantly different from your actual gallons. In that case, please contact Heatec for a custom-made levels vs. gallons table applicable to your tank.

CHECKING YOUR RADAR AND GAUGE BOARD
You should periodically verify the accuracy of the levels indicated by your radar and gauge board. A build-up of either asphalt residues or moisture on the antenna of the radar sensor can cause erroneous indications. Likewise, a build-up of asphalt residues on the cable that supports the float of the gauge board can cause it to operate improperly.

The usual way of checking that your radar is accurate is with a measuring tape. As explained earlier, measure the distance from the top of the tank to the surface of the asphalt. Then subtract this distance from the inside height of the tank as indicated in Figure 4. This should closely agree with the level indications you see on your radar sensor and the indications on the gauge board.