Before the pressure-welded plate heat exchanger is put into operation, maintenance personnel must confirm that all interface flanges are tightened without leakage, and that pressure gauges and thermometers are within their valid calibration periods. Check whether the flow channels between plates are clean to avoid blockage caused by residual welding slag or foreign matter. For equipment that has been out of service for a long time, the insulation resistance should be measured. If it is below the specified value, it can be dried in an oven at about 200°C, or heated by applying power at reduced voltage, until the insulation resistance recovers.
During operation, the inlet and outlet temperatures, pressures, and flow rates should be recorded, and compared with the design conditions to judge changes in heat exchange efficiency. If the pressure drop rises abnormally, it may be due to scaling or blockage in the flow channels, and cleaning should be arranged. During cleaning, avoid using sharp tools to scrape the plates; chemical cleaning or high-pressure water flushing is recommended. Monitor fluctuations in the medium temperature to prevent overheating from causing seal gasket aging or welding stress concentration.
After shutdown, the internal medium should be drained completely to prevent corrosive liquid from remaining. For detachable pressure-welded plate heat exchangers, regularly check the elasticity of the sealing gaskets and replace them if necessary. During long-term shutdown, protective gas or dry air should be charged to avoid rusting caused by a humid environment. Maintenance records must be archived to facilitate tracing of equipment status.
If external leakage occurs, the common causes are gasket aging or plate deformation, and the equipment must be shut down to replace the components. Internal leakage is mostly caused by plate cracks or perforation, which can be judged by a one-side pressure-holding test. During handling, disassembly under pressure is strictly prohibited; operation must be carried out after pressure relief and cooling. When replacing plates, ensure the model is consistent to avoid mixing accessories from different batches.
Before maintenance, the power supply must be cut off and lockout/tagout must be applied, and it must be confirmed that the equipment has cooled to ambient temperature. Operators should wear protective gloves and goggles to prevent burns from residual medium. Cleaning agents must be diluted according to the instructions to avoid reacting with the plate material. Regularly calibrate the safety valve and pressure switch to ensure overpressure protection is effective.
