Many different bacteria species may exist in cooling water systems. Some of the problems caused include severe bacterial slimes and fouling, sulfuric acid, underdeposit corrosion and health hazards. As water is heated and converted into steam, contaminants brought into a boiler with makeup water are left behind. The boiler functions as a distillation unit, taking pure water out as steam, and leaving behind concentrated minerals and other contaminants in the boiler Scale forms as a result of the precipitation of normally soluble solids that become insoluble as temperature increases. Some examples of boiler scale are calcium carbonate, calcium sulfate, and calcium silicate.
Corrosion is a general term that indicates the conversion of a metal into a soluble compound.
Oxygen pitting corrosion, seen on the tubes and in the pre-boiler section. Low pH corrosion, seen in the condensate return system. Corrosion of either type can lead to failure of critical parts of the boiler system, deposition of corrosion products in critical heat exchange areas, and overall efficiency loss. Carryover is caused by either priming or foaming. Priming is the sudden violent eruption of boiler water, which is carried along with steam out of the boiler, usually caused by mechanical conditions.