For Positive Displacement Pumps:
- Fill the application equipment with emulsified asphalt.
- Connect one end of a hose to the emulsified asphalt pump outlet and connect the other to a container sufficiently sized to hold the emulsified asphalt used during calibration. Run the emulsified asphalt pump long enough to fill the connecting hose to ensure that all calibration checks are consistent.
- Note the identity of the unit for which calibration is being completed as well as the date on the Emulsified Asphalt Calibration worksheet.
- There are 2 options for determining the sample weights of the emulsified asphalt. Pick the option that will be used to determine how to complete the worksheet.
Option 1: The application equipment is filled with emulsified asphalt and weighed on a certified truck scale before and after each sample run in order to calculate the sample size. For this option, note the start weight in the “Weight A” column and the end weight in the “Weight B” column on the worksheet. This is the Option displayed in the Emulsified Asphalt Calibration worksheet example.
Option 2: A container, into which the emulsified asphalt is pumped, is weighed on a certified platform scale before and after each sample run in order to calculate the sample size. For this option, note the start weight in the “Weight B” column and the end weight in the “Weight A” column on the worksheet. - Zero the aggregate counter before each sample run.
- Note the start weight in the appropriate space on the worksheet. Pump the emulsified asphalt for a minimum of 50 counts of the aggregate counter. The resulting sample size should be large enough to ensure greater than 2% accuracy. Minimum sample size is calculated by dividing scale accuracy by 2%.
Examples of minimum sample size include: 50 lbs. of emulsified asphalt if the scale accuracy is ± 1 lb., 100 lbs. for ± 2 lb. accuracy, 250 lbs. for ± 5 lb. accuracy, or 1000 lbs. for ± 20 lb. accuracy.
- Once pumping is complete, remove the connecting hose from the container and note the end weight in the appropriate space on the worksheet.
- Determine the net weight (weight A minus weight B) for the first sample of emulsified asphalt pumped. Divide the net weight by the number of counts of the aggregate belt and record the lbs./count for the first sample.
- Repeat Steps 5-8 for two additional sample runs, recording the results on the worksheet. It is important to run three calibration samples and then to average the lbs./count of the three samples as illustrated in the completed Emulsifier Asphalt Calibration worksheet.
For Variable Speed Constant Displacement Pumps:
- Set the emulsified asphalt pump to the factory recommended setting and lock in place.
- Follow Steps 1-9 above for calibrating the variable speed constant displacement pump.
- Once calibration is completed, the pump should be locked in place to avoid accidental changes to the flow rate setting.
All emulsified asphalt pumps, regardless of type, should deliver consistent weights so that, once the three runs are averaged, any individual weight should be within ± 2% of the average.
Example: The average emulsified asphalt lbs./count is 4.0. 2% of 4.0 is 0.1, so each individual run should be between 3.9 to 4.1 lbs./count.
If the pump is variable speed constant displacement, over the course of the job, occasionally verify that the pump setting still matches what was used during calibration.
Inspector’s Note: If the variation is too great and the calibration process must be repeated, emulsified asphalt used in the initial calibration runs should not be used again. Emulsified asphalt that has been pumped back and forth between the container and truck will contain entrained air which will lead to incorrect weights.
Inspector’s Note: Emulsified asphalt pumps vary among manufacturers. Pumps are either a positive displacement type or a variable speed constant displacement type which can be mechanically set to various rates of flow. Since a variable speed constant displacement pump will not normally be changed during the project, a calibration is necessary only for the setting that the contractor intends to use. Variable speed constant displacement pumps should be equipped with a lock. Calibrate emulsified asphalt to the head pulley revolutions which are displayed on the aggregate counter.
Example of an Emulsified Asphalt Certificate of Analysis (CoA)
