The mineral and organic substances present in natural water supplies vary greatly in their relative proportions, but are principally comprised under the carbonates, sulphates and chlorides of lime, magnesia and sodium, iron and aluminum salts, silicates, mineral and organic acids, and the gases oxygen and carbon dioxide.
Boiler scale is formed from the carbonates and sulphates of lime and magnesia, and from the oxides of iron, aluminum and silicon and it will result in:
Boiler scales are dangerous long before it reaches
this thickness. A very thin scale can cause tube failure due to overheating.
Scale has about one-fortyeighth of the heat conductivity of steel.
Accumulation of boiler scale, or incrustation, is objectionable in any and every form of boiler, for irrespective of the wear and tear of the boiler and the repairs which it entails, it is the cause of loss in efficiency. Diligent care should be exercised in preventing scale or incrustation accumulating in the boilers. The cleaning of the boilers internally should consequently receive every care.