Plate heat exchangers can be generally divided into water - water exchange and steam - water exchange. Water - water exchange ways of cold and hot medium is water, and hot and cold water temperature difference is not big, probably between 70 ~ 90 ℃, scaling situation are basically the same on both sides; Steam-water heat exchange medium is water vapor, generally not easy scaling, cold medium is water, the temperature about 90 ℃, easy to scale. The scale can be divided into scale and dirt, especially scale. Various salts thermal decomposition scale is mainly dissolved in water solubility decrease and crystal deposition on the heat transfer piece, usually in the form of carbonate, phosphate, sulfate, and silicates, such scale crystallization density, more hard, difficult to remove; Dirt is generally made up of very granular mud, dust, insoluble salts of gunk, colloidal hydroxides, sundry detritus, corrosion products, grease, especially the body of bacteria and algae and its sticky secretions, etc, the scale larger, loose texture, soft, clear more easily.

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