What are the preparations for cleaning plate heat exchanger? The scale analysis of 21 plate heat exchanger before cleaning can be divided into two ways: water water exchange and steam water exchange. The water water exchange mode is water, and the temperature difference between the cold and hot water is not large. The cleaning of the Beijing heat exchanger is about 70-90 ℃, and the scaling on both sides is basically the same; The heat medium of steam water exchange mode is water steam, which is not easy to scale in general. The cold medium is water, and the temperature is about 90 ℃, and it is easy to scale. The scale samples can be divided into scale and dirt, especially scale. The scale is mainly composed of various salts dissolved in water, which are decomposed by heat and the solubility is reduced, and the crystallization is deposited on heat transfer plate, which is usually carbonate, phosphate, sulfate and silicate. The scale is compact and hard to remove; The dirt is generally composed of fine particles of mud sand, dust, insoluble salt mud, colloidal hydroxide, debris, corrosion products, oil pollution, especially the body of bacteria and algae and their viscous secretion. This scale is large in volume, loose and soft in texture, and easy to remove [1]. 21 2. The selection of cleaning methods and cleaning processes for plate heat exchanger: the scale sample of plate heat exchanger is mainly water scale, which is relatively hard, and is firmly combined with heat transfer plate, so it is difficult to remove by physical method. Therefore, acid cleaning method in chemical cleaning is selected to remove scale. According to the fouling, aging degree and user requirements, the chemical cleaning of plate heat exchanger can be divided into two methods: disassembly cleaning and non disassembly cleaning. The cleaning and scaling removal is complete and the effect is good, but the work quantity is large and the process is complex, and it is easy to cause the leakage of heat exchanger and damage of parts and accessories; Cleaning and scaling without dismantling is not thorough, but the labor volume is small.