The solution to the failure of excessive pressure drop in the maintenance of plate heat exchanger_
The precautions for 984 plate heat exchanger maintenance when the pressure drop is too large, mainly talk about the reasons for the excessive pressure drop of the plate heat exchanger, as well as the handling methods and precautions during maintenance. Causes of excessive pressure drop ① The operating system pipeline is not normally purged, especially when many dirt (such as welding slag, etc.) in the newly installed system pipeline enters the inside of the plate heat exchanger, due to the interception of the plate heat exchanger flow passage The area is relatively narrow, and the sediment and suspended matter in the heat exchanger gather at the corner hole and the diversion area, which causes the area of u200bu200bthe flow channel to be greatly reduced, causing the main pressure loss in this part. ② When the plate heat exchanger is selected for the first time, the area is too small, which causes the flow velocity between the plates to be too high and the pressure drop is too large. ③ After the plate heat exchanger has been running for a period of time, the pressure drop is too large due to fouling on the plate surface. Example: In 2000, our factory provided a BR10 plate heat exchanger for users in Xinjiang, which is used in a central heating system for water-to-water heat exchange. The design temperature of the primary water supply is 130°C. In the design and selection of heat exchanger, the heat transfer coefficient is high, close to 5 500 w/(rn ·K), but actually should be 3 500 w/(rn ·K). At the same time, when the design unit selected the pump, the flow margin was too large, causing the flow velocity between the medium plates on the secondary side of the heat exchanger to exceed 1 m/s, and the actual operating pressure drop was 0.2 to 0.3 MPa, making the hydraulic balance of the secondary network serious. Imbalance. Plate heat exchanger maintenance and treatment methods ① Remove dirt or plate fouling in the heat exchanger flow channel. For the newly operating system, clean it once a week according to the actual situation. When cleaning the scale on the surface of the board (mainly CaCO3), use 0.3 sulfamic acid solution or 0.8 nitric acid solution containing 0.3 urotropine, 0.2 aniline, and 0.1 potassium thiocyanate as the cleaning solution, and the cleaning temperature is 40 ~ 60 ℃. When not disassembling the equipment for chemical immersion cleaning, open the cold medium inlet and outlet of the heat exchanger, or install DN25 cleaning ports on the medium inlet and outlet pipes when installing the equipment, inject the prepared cleaning solution into the equipment, and clean with water after soaking Clean the residual acid solution to make the pH ≥7. When disassembling and cleaning, soak the plate in the cleaning solution for 30 minutes, then use a soft brush to lightly brush the scale, and then clean it with clean water. Avoid damaging the plates and rubber pads during the cleaning process. If the mechanical backwashing method without disassembly is adopted, a nozzle should be connected to the medium inlet and outlet pipes in advance, the equipment is connected with the mechanical cleaning vehicle, and the cleaning fluid is injected into the equipment in the opposite direction of the medium flow. The cycle cleaning time is 10-15 min , The flow rate of the medium is controlled at 0.05～0.15 m/s. Then circulate the clean water several times to control the Cl mass concentration in the clean water below 25 mg/I. ② As far as possible, the secondary circulating water should be soft water that has undergone softening treatment. Generally, the suspended solids concentration in the water should not be greater than 5 mg/L, the impurity diameter should not be greater than 3 mm, and the pH ≥ 7. When the water temperature is not more than 95℃, the concentration of Ca and Mg should not be more than 2 mmol/L; when the water temperature is more than 95℃, the concentration of Ca and Mg should not be more than 0.3 mmol/L, and the mass concentration of dissolved oxygen should not be more than 0. 1 mg/L. ③For the central heating system, the method of supplementing water once and twice can be used.