Analysis of four common failures in plate heat exchanger maintenance_
Analysis of four common failures in the maintenance of plate heat exchangers
What are the more common problems in the maintenance process of 1066 plate heat exchanger? No matter which brand of plate heat exchanger, it has been used for a long time, and some failures are unavoidable. Today, we will talk about the analysis of common failures in plate heat exchanger maintenance, including internal leakage, external leakage, excessive pressure drop, and heating temperature. If you can't meet, let's talk about the failures in these four areas first, and see if you have also encountered such failures in the plate heat exchanger. First of all, I will talk about one of the more common faults, which is the internal leakage. I believe that many users have encountered this situation, especially the frequently used plate heat exchanger. The main reasons for internal leakage are: improper selection of plates leads to cracks or perforations due to plate corrosion; operating conditions do not meet the design requirements; residual stress after cold stamping of plates and excessively small clamping dimensions during assembly resulting in stress corrosion; plates; There is a slight leakage at the leakage groove of the sheet, which causes the harmful substances in the medium to concentrate and corrode the sheet, forming an internal leakage. So how to solve the problem of internal leakage, the treatment method: replace the cracked or perforated plate, use the light transmission method to find the crack of the plate on the spot; adjust the operating parameters to meet the design conditions; clamp the heat exchanger during maintenance and assembly The size should meet the requirements, not as small as possible; the plate materials should match reasonably. Causes of external leakage: the tight dimensions are not in place, the dimensions everywhere are uneven (the dimension deviation should not be greater than 3 mm) or the clamping bolts are loose; part of the gasket is out of the sealing groove, the main sealing surface of the gasket is dirty, and the gasket is Damage or aging of the gasket; deformation of the plate and misalignment of the assembly causing the running pad; there are cracks in the sealing groove of the plate or the second sealing area. Treatment method: In the no-pressure state, re-clamp the equipment according to the clamping size provided by the manufacturer. The size should be uniform, and the deviation of the compacted size should not exceed ±0.2N (mm) (N is the total number of plates). The parallelism between the compression plates should be kept within 2 mm; mark the leaking parts, and then the heat exchanger is disassembled and checked and solved one by one, reassemble or replace the gaskets and plates; disassemble the open heat exchanger and align the plates. Repair or replace the deformed part of the plate. When there are no spare parts for the plate, the deformed plate can be temporarily removed and then reassembled for use; when reassembling the disassembled plate, the plate surface should be cleaned to prevent dirt from adhering to the gasket sealing surface. The pressure drop is too large, the reason is that the pipeline of the operating system is not normally purged, especially when a lot of dirt (such as welding slag) in the pipeline of the newly installed system enters the inside of the plate heat exchanger. The area is narrow, the sediment and suspended matter in the heat exchanger gather at the corner hole and the diversion area, which causes the flow channel area to be greatly reduced, causing the main pressure loss in this part; plate heat exchanger for the first time The area is too small during model selection, resulting in excessively high flow velocity between the plates and a large pressure drop; after a period of operation of the plate heat exchanger, the pressure drop is too large due to fouling on the plate surface. Treatment method: remove the dirt or plate fouling in the flow channel of the heat exchanger. For the newly operating system, clean it once a week according to the actual situation; the secondary circulating water is preferably soft water after softening treatment, and suspended solids in the water are generally required The mass concentration is not more than 5 mg/L, the impurity diameter is not more than 3 mm, and the pH is ≥ 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 The concentration should be no more than 0.3 mmol/L, and the mass concentration of dissolved oxygen should be no more than 0.1 mg/L; for the central heating system, the method of replenishing water once can be used; the heating temperature cannot meet the requirements: cause Insufficient medium flow on the primary side causes a large temperature difference on the hot side and a small pressure drop; low temperature on the cold side and low temperatures at the cold and hot ends; uneven flow distribution of multiple plate heat exchangers operating in parallel; serious internal scaling of the heat exchanger . Treatment method: increase the flow rate of the heat source or increase the diameter of the heat source medium pipeline; balance the flow of multiple plate heat exchangers operating in parallel; disassemble the plate heat exchanger to clean the surface of the plate fouling. The above are the four common failures encountered during the maintenance of plate heat exchangers, and the correct handling methods, but we still hope that when we encounter the failure of plate heat exchangers, we can promptly ask dedicated plate heat exchanger maintenance personnel to do it. Machine maintenance operations.