Hardness

Definition

The concentration of dissolved calcium and magnesium in water, the primary scaling species boilers cannot tolerate. Boiler feedwater hardness is treated as non-detect.

Hardness is removed from makeup by softening to limit scale, but condensate contamination from a process leak or tube failure can let hardness enter a boiler. Hardness deposited on heat-transfer surfaces forms scale, which in turn promotes under-deposit corrosion and drops efficiency. It is a key input condition tracked on every free body diagram.

Related concepts

Sequestration · Alkalinity · Saturation pH

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Part of The Blueprint of Water · 🧪 chemistry