Chemical Mass Consumed Over a Period

A treatment programme is quoted in dollars per year, so the feed rate has to become a mass before anyone can price it. The arithmetic is trivial — 12 lb/day of inhibitor over a 365 day contract is 4380 lb, about four 55-gallon drums at a typical 9.5 lb/gal — but it is the step where a service contract stops being chemistry and starts being logistics: drum count, delivery frequency, bunded storage, and the shelf life of whatever is left in December. Run backwards it is the reconciliation every route does at year end: 876 kg delivered against 8760 operating hours is an average feed of 0.1 kg/h, and if the pump was set for 0.25 kg/h then either the pump was off or the product went somewhere it should not have.

Get the basis right before you multiply. Chemical is consumed by the flow that carries it out of the system — blowdown plus drift — and not by makeup, because evaporation leaves every molecule of inhibitor in the basin; sizing an annual budget on makeup on a typical tower overstates it three- to four-fold. Then check the year, since a seasonal tower has no December consumption at all, and check whether the ppm you multiplied was as-product or as-active: 100 ppm of a 20% active blend is 20 ppm of active, and a five-fold error here is the same size as the makeup mistake and just as easy to make. The solver can report the answer as a rate in kg/yr, lb/yr or t/yr as well as a mass, which is the form a purchase order actually wants.