Causes and method for handling corrosion and deposition in boilers

Corrosion and deposition in boilers are quite popular. Let’s identify causes and ways to prevent this phenomenon from affecting quality of boilers.

Corrosion is a general term referring to the conversion of a metal into a dissolved compound. To boilers, corrosion is the process to change steel into rusts.

There are 2 common types of corrosion in boilers:

1. Corrosion due to oxidation: generally found on tubes and water pipes.
2. Corrosion due to low pH level: generally found in condensation system.

The corrosion due to one of the two types may cause damages to parts of the boiler system. What produced from corrosion process causes blocks and obstructions which adversely impact the temperature exchange and causes temperature loss. 

Boiler deposition phenomenon

When water is heated and turned into steam, the pollutants go with feed-water and deposit in the boiler. The function of a boiler is similar to that of a distiller, which creates distilled steam water and leaves condensed minerals and many other pollutants accummulated in the boiler. The dissolved solids under the impact of temperature turn into non-dissolve, causing deposition.

Types of typical boiler deposition including calcium carbonate (CaCO3), calcium sulfate (CaSO4), and calcium silicate (CaSiO3).

Deposition inside the tube creates a layer of heat insulation, limiting the heat transfer to water in the tube. This, if occurs in a long time, will cause overheating and damaging to the tubes. 

To prevent boiler deposition, the concentration of dissolved solids in the feed water must decrease to the allowable limit. The higher preassure and temperature of the boiler, the stricter requirements are forfeed-water treatment.

Solids must also be continuously discharged from boilers using discharge system or periodical blowdown.

In conclusion, quality of boilers’ feed water treatment is crucial to ensure that boilers could operate as long as its designed lifespan. Water with poor quality is among the “terminators” of boilers.