Causes and solutions for large pressure drop of brazed plate heat exchanger
Causes of large pressure drop in plate heat exchangers
1. the operating system pipeline is not properly purged, especially in the new installation system pipeline, many dirt (such as welding slag) into the interior of the plate heat exchanger, due to the plate heat exchanger The cross-sectional area of the flow channel is narrow, and the sediment and suspended matter in the heat exchanger gather in the corner hole and the flow guiding area, so that the flow channel area at the place is greatly reduced, and the pressure is mainly lost in this part.
2, after the plate heat exchanger has been running for a period of time, the pressure drop caused by the surface fouling of the plate is too large.
3. when the plate heat exchanger is selected for the first time, the area is too small, causing the flow rate between the plates to be too high and the pressure drop to be too large.
Processing method for large pressure drop of plate heat exchanger
1. remove dirt or plate fouling in the heat exchanger flow channel, for the newly run system, clean once a week according to the actual situation. When cleaning the surface scale of the plate (mainly CaCO3), use a 0.3 sulfamic acid solution or a 0.8 nitric acid solution containing 0.3 urotropin, 0.2 aniline, 0.1 potassium thiocyanate as the cleaning solution, and the cleaning temperature is 40-60 °C. When disassembling the equipment for chemical immersion cleaning, open the heat exchanger inlet and outlet of the heat exchanger, or install the DN25 cleaning port on the medium inlet and outlet nozzles when installing the equipment, inject the prepared cleaning liquid into the equipment, and wash it with water after immersion. Clean the residual acid to make pH≥7. When disassembling the cleaning, soak the plate in the cleaning solution for 30 minutes, then use a soft brush to lightly scale the scale, then rinse it with water. Avoid damage to the plates and rubber pads during the cleaning process. If the mechanical backwashing method is not disassembled, a nozzle shall be connected to the medium inlet and outlet pipes in advance, and the equipment shall be connected to the mechanical cleaning vehicle, and the cleaning liquid shall be injected into the equipment in the opposite direction of the medium flow, and the circulation cleaning time is 10 to 15 minutes. The medium flow rate is controlled at 0.05 to 0.15 m/s. After that, it is recycled several times with clean water to control the mass concentration of Cl in the water below 25 mg/I.
2. secondary circulating water is good to use soft water after softening treatment, generally requires the concentration of suspended solids in water is not more than 5mg / L, impurity diameter is not more than 3mm, pH & ge; When the water temperature is not more than 95 °C, the concentration of Ca and Mg should be no more than 2mmol/L; when the water temperature is greater than 95°C, the concentration of Ca and Mg should be no more than 0.3mmol/L, and the concentration of dissolved oxygen should be no more than 0.1mg/L.
3. for the central heating system, you can use a secondary water supply method.