An equilibrium pH value used in calculating the scaling indexes (LSI, RSI, PSI). It uses the values of TDS (expressed from μmhos – to convert μmhos to a TDS value for cycled cooling water, multiply the μmhos by 0.8); Temperature (the highest temperature that the cooling water is exposed to); Calcium Hardness, and Total Alkalinity. Often the only temperature information available is the bulk water temperature, which is not the highest temperature in the system. A skin temperature value should always be used when known. If the skin temperature is not known, we add a “safety factor” of 20° F to the maximum bulk water temperature (up to 115° F). If the bulk water temperature is greater than 115° F, then we use that value to determine the temperature factor. Lookup tables of factors for each of the four parameters are used to obtain the values used in the formula:
pHS = (9.3+A+B) – (C+D)
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