Well, a scale is a deposit formed over the heat transfer surface when the solubility limits of the constituents of water are exceeded resulting in the precipitation of compounds over the surface. Scales are nothing but salts of Calcium and Magnesium (existing primarily in the form of sulphates or carbonates), which are highly insoluble in water.
Hardness of water is the major culprit behind scale formation.
The major problems associated with scaling are:
- For the same boiler output, the quantity of fuel required would be more as compared to a boiler without scales.
- The conductivity of sodium sulphate scale is about one hundredth that of steel thus causing hindrance in the heat flow considerably. Even a thin layer of scale on the metallic surfaces can reduce the boiler efficiency by 20%.
- The metal becomes increasingly hotter due to resistance in heat flow and thus the metal becomes more prone to deformation and rupture effect.
- Layers of scale act as an insulator, reducing the heat transfer rate from the hot zones to the water.
Boiler Scaling Problem:
You should consider following our tips and tricks for your boiler scaling problem:
- If the scales loosely adhere to the surface, a wire brush or scraper can easily remove them
- Thermal shocks can be given to the scale having “brittle” nature
- Frequent blow-down operations can be beneficent in removing scales which are loosely held on to the surface of the boiler
- Hard scales require chemical treatment. For e.g. Calcium Sulphate scales can be removed by adding EDTA
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