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Causes and solutions for excessive pressure drop in heat exchangers. Cause 1: The pipelines of the operating system were not properly flushed; in particular, many contaminants such as welding slag ended up inside the plate heat exchanger. Due to the narrow flow area within the plate heat exchanger, deposits and suspended particles accumulate in the corner holes and guide areas, which significantly reduces the flow area in those regions and results in the majority of pressure loss occurring there. 2. When selecting a plate heat exchanger for the first time, if its area is too small, the flow velocity between the plates becomes too high, resulting in a large pressure drop. 3. After operating for a period of time, plate heat exchangers experience excessive pressure drop due to scaling on the surface of the plates. The plate heat exchanger is disassembled for thorough inspection and troubleshooting, after which the gaskets and plates are reassembled or replaced. Treatment method 1: Remove dirt or scale from the heat exchanger channels; for newly operational systems, clean them once a week depending on actual conditions. Clean the scale on the surface of the plate (mainly referring to CaCO3). ) At that time, a cleaning solution containing 0.3% aminosulfonic acid or an 0.8% nitric acid solution containing 0.3% urotropine, 0.2% aniline, and 0.1% potassium thiocyanate is used, with a cleaning temperature of 40–60°C. When performing chemical immersion cleaning without removing the equipment, it is necessary to open the inlet and outlet ports for the cold medium in the heat exchanger; or, when installing the equipment, DN25 cleaning ports should be installed on the medium inlet and outlet connections. The prepared cleaning solution is then poured into the equipment, and after immersion, the remaining acidic liquid is washed away with clean water to ensure that the pH level is ≥7. When disassembling for cleaning, soak the plates in the cleaning solution for 30 minutes, then gently brush off the scale with a soft brush, and finally rinse thoroughly with clean water. During the cleaning process, care should be taken to avoid damaging the plates and rubber gaskets. If the mechanical backwashing method without disassembly is used, a fitting should be installed in advance on the inlet and outlet pipes of the medium, connecting the equipment to a mechanical cleaning vehicle; the cleaning fluid is then injected into the equipment in the opposite direction to the flow of the medium. The cleaning cycle lasts 10–15 minutes, with the flow rate of the medium controlled at 0.05–0.15 m/s. Finally, rinse several times with clean water to keep the mass concentration of Cl in the water below 25 mg/L. 2. It is preferable to use softened water for the secondary circulating water; generally, the mass concentration of suspended solids in the water should not exceed 5 mg/L, the diameter of impurities should not be greater than 3 mm, and the pH value should be ≥ 7. When the water temperature is 95°C or less, the concentrations of Ca and Mg should be 2 mmol/L or less; when the water temperature is above 95°C, the concentrations of Ca and Mg should be 0.3 mmol/L or less, and the dissolved oxygen concentration should be 0.1 mg/L or less. 3. For centralized heating systems, the method of replenishing water to the secondary system once can be adopted.