Boiler water

These solid deposits thermally insulate heat exchange surfaces initially decreasing the rate of steam generation, and potentially causing boiler metals to reach failure temperatures.

Chemicals may be added to maintain pH levels minimizing water solubility of boiler materials while allowing efficient action of other chemicals added to prevent foaming, to consume oxygen before it corrodes the boiler, to precipitate dissolved solids before they form scale on steam-generating surfaces, and to remove those precipitates from the vicinity of the steam-generating surfaces.

Hard water treated this way causes a fairly high concentration of suspended solid particles within the boiler to serve as precipitation nuclei preventing later deposition of calcium sulfate scale.

[8] Coordinated control of pH and phosphates attempts to limit caustic corrosion occurring from concentrations of hydroxyl ions under porous scale on steam generating surfaces within the boiler.

Solubility of these complex ions may reduce blowdown requirements if anionic carboxylate polymers are added to control scale formation.

Potential decomposition at high temperatures limits chelant use to boilers operating at pressures less than 1,500 pounds per square inch (10,000 kPa).

A deaerator is often used to convert condensate to feedwater by removing potentially damaging gases including oxygen, carbon dioxide, ammonia and hydrogen sulfide.

[15] Inclusion of a polisher (an Ion exchange vessel) helps to maintain water purity, and in particular protect the boiler from a condenser tube leak.

[17] Hard water intended for low-pressure boilers may be softened by substituting sodium[18] for divalent cations of dissolved calcium and magnesium most likely to cause carbonate and sulfate scale.