Figure 5-12. Electrical control cabinet.
5-10. DETERMINING CHEMICAL DOSAGES
The TM for each model WPU prescribes the chemical dosages required for
proper treatment under normal conditions. Since the chemical composition of water will
vary from time to time, these dosages vary. The base charge, which is the initial
mixture of chemical and water added to the chemical solution or slurry feeder (see para
5-6), remains constant. The rate of feed, which is set on the feeder controls (see figs.
5-8 and 5-9), varies with the chemical characteristics of the particular water being
treated and is adjusted during operation to obtain optimum results.
a. Calibration Charts. Mounted on the control cabinet of the WPU, for ready
reference, are four calibration charts identical to those in the TM to be used for
determining the base charge and feeder control setting for each chemical used by the
erdlator. Figure 5-13 illustrates the calcium hypochlorite calibration chart for the 1,500