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Nonlinear Chemical Doser Calibration Procedure

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Figure 1: Lever Arm Legend

Purpose: We need to make sure that our lever arm is able to adjust the alum dosage automatically for the entire flow range of the plant flow. Since alum dosage is ultimately set by the float moving up or down the entrance tank as plant flow changes, we need to make sure the lever arm can respond to minimum and maximum water height in the entrance tank, which corresponds to the minimum and maximum plant flow rate. Head loss in the plant determines the difference between minimum and maximum entrance tank water height. Greater the head loss in the tank, greater would be the difference between minimum and maximum water height given any plant flow rate. Even though we would design the lever arm based on analytically calculated head loss, there is bound to be a minor difference between calculated minimum and maximum water flow and the actual heights. Calibration will also minimize the sources of error mentioned above. These are the calibration steps:

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Step 3. Find out what dosage is most commonly used. Calibrate the float weight on the dosage that is most commonly used. Use the chart below:

Table 1: Float Calibration Mass

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