The plate bundle channels of a plate-and-shell heat exchanger are relatively narrow, so the inlet and outlet pressure difference should be recorded regularly during operation. When the pressure difference rises to 1.5 times the initial design value, chemical cleaning or mechanical unclogging can be arranged. Before cleaning, confirm that the medium has been drained and replaced to an acceptable level to avoid reactions between residual substances and the cleaning solution.
Gasket selection must correspond to the actual working conditions: nitrile gaskets are suitable for oil and general water media below 80°C; EPDM gaskets are suitable for hot water and steam conditions below 120°C; fluororubber gaskets can be used for corrosive media below 180°C. During operation and maintenance, if gaskets are found to be hardened, cracked, or leaking, the equipment should be shut down for replacement, and tightening under pressure is not allowed.
Plate materials can be 304, 316L stainless steel, or titanium. On site, the plate surface should be inspected regularly according to the corrosiveness of the medium, with special attention to the areas near the inlet and outlet and the sealing groove area. Titanium plates have good adaptability to media containing chloride ions, but long-term contact with fluorides should be avoided.
When reassembling after maintenance, bolts should be tightened evenly in diagonal sequence in multiple passes to avoid deformation of the plates caused by over-tightening on one side. The pressure test is recommended to be conducted at 1.25 times the design pressure, with a holding time of no less than 30 minutes, observing whether there is leakage at each sealing point.
Daily operation should record changes in inlet and outlet temperature, pressure, and flow rate. If there is a sudden rise in pressure difference or a decrease in temperature efficiency, first check the filter and pipeline blockage, then inspect the internal scaling of the plate bundle. During shutdown, it is recommended to drain accumulated liquid and keep the equipment dry.
