We have seen that the deposits found in a cooling system are of two types:
– hard and adhesive deposits which all are scale of mineral origin;
– clogging deposits which can be powdery and can give silt or sludge, when the circulation velocity of the water is not sufficient for keeping them suspended. They are mostly of the mineral origin. These deposits can be more or less adhesive and more or less soft, but, when they are of the biological origin, they can take any kind of appearance.
In fact, they are often constituted by a mixture of the elements of organic, mineral and biological origin.