Chemical dosing rate
Dosing pump rate in L/h and mL/min from a ppm target — product or active ingredient, dilution, pump stroke, drums a month and yearly cost.
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How this calculator works
1 ppm is 1 mg/L, or 1 g in every m³ of water, so the product needed is simply ppm × flow: at 1 ppm, 100 m³/h takes 100 g/h. A dose stated as active ingredient — free chlorine, phosphate, polymer solids — is divided by the product strength, and the result turned into litres per hour with the specific gravity, into a pump stroke setting, into drums or IBCs a month and into a yearly cost. In a recirculating cooling system the chemical leaves only with the blowdown and drift (evaporation leaves it behind), so the continuous dose is set on those losses, with a shot dose to bring the system volume up to strength at start-up.
Example: 2 ppm of chlorine into 100 m³/h of water from sodium hypochlorite at 12.5 % by mass (specific gravity 1.21): 16 ppm of product, 1.60 kg/h, 1.32 L/h (22 mL/min) — 13 % of a 10 L/h metering pump's stroke, 32 L a day, under one IBC a month and about USD 4,500 a year at USD 0.35/kg. For a cooling tower losing 3 m³/h to blowdown and drift, 20 ppm of inhibitor is 0.06 kg/h, plus a 60 kg shot to bring 1,500 m³ up to 40 ppm. The arithmetic was checked by hand and in an independent script.
Limits: chlorine and other oxidizers are also consumed by the water's demand, so the dose that keeps a residual is higher than the residual itself — measure it. Hypochlorite loses strength in storage, faster when warm. Keep metering pumps between about 10 and 90 % of stroke for accuracy. Follow your chemical supplier's dose and the product's safety data sheet. For cooling-water cycles and blowdown, see the water balance calculator.