During field inspections, leakage traces are often found on the sealing gaskets between the plates of plate-and-shell heat exchangers, especially when the medium temperature approaches the upper temperature limit of the gasket, the probability of leakage increases. Such problems are often not due to gasket quality defects, but rather insufficient consideration of operating parameters and structural matching during the selection stage. Compared with fully welded plate heat exchangers, the plate-and-shell structure can be disassembled for inspection, and the sealing gasket is a replaceable part. However, if reasonable margins are not reserved according to actual temperature and pressure during selection, leakage will repeatedly occur during operation. Compared with shell-and-tube heat exchangers, plate-and-shell heat exchangers have higher heat transfer efficiency at the same pressure drop, but are more sensitive to medium cleanliness, requiring trade-offs during selection.
Before procurement, medium composition, inlet temperature, outlet temperature, working pressure, and flow rate should be provided. These parameters directly determine the plate material, gasket material, and flow channel combination. The shell side can withstand higher pressure, while the plate side is suitable for clean media or media containing a small amount of particles. If the medium contains particles or is prone to scaling, it should be evaluated whether the plate side requires widened flow channels or additional filtration. When requesting quotations, technical engineers are advised to also specify whether there is temperature cycling, start-stop frequency, and on-site installation space limitations, so as to match a reasonable number of plates and port orientation.
Shell-and-tube heat exchangers have a wide pressure and temperature resistance range, but a smaller heat transfer area per unit volume and a larger footprint; fully welded plate heat exchangers have no gaskets and are suitable for high temperature and high pressure with low leakage risk, but cannot be disassembled for inspection and are difficult to clean. Plate-and-shell heat exchangers fall between the two: the shell side has higher pressure-bearing capacity than ordinary plate types, and the plate side can be disassembled for cleaning, making them suitable for occasions requiring regular inspection of gaskets or plate scaling. If the medium temperature is close to the upper temperature limit of the gasket for a long time, fully welded structures or gasket materials with higher temperature resistance should be given priority.
During operation, it is recommended to check the sealing gaskets between plates for leakage traces every shift, with emphasis on operating conditions where the medium temperature approaches the upper temperature limit of the gasket. If leakage is found, the unit should be shut down and depressurized, then the clamping bolts should be tightened in a diagonal sequence to avoid deformation of the plates caused by over-tightening on one side. If leakage persists after tightening, the gasket should be replaced and the sealing surface of the plates should be checked for scratches. The inspection records should note the leakage location and frequency of occurrence to provide a basis for subsequent selection adjustments.
