Pressure fluctuations in cooling water systems are usually modest, yet after one or two years in service, heat exchangers often develop connection leaks and seal failures between plates; during maintenance, the gaskets are found to have aged and the entire unit must be disassembled—such phenomena are not uncommon in procurement follow-up visits. The problem often lies not in the installation stage but in the judgment of connection methods and operating condition fluctuations during the selection stage. The following addresses several questions frequently asked by procurement personnel and provides a comparative explanation of welded plate heat exchangers versus gasketed and shell-and-tube alternatives.
Gasketed plate heat exchangers rely on rubber gaskets for sealing; gaskets are wearing parts, and temperature cycling and medium attack cause them to harden and take a permanent compression set, typically requiring periodic replacement with substantial disassembly and reassembly effort. Welded plate heat exchangers use welded connections between plates, eliminating the gasket sealing element, and under applicable operating conditions can reduce downtime maintenance caused by gasket aging. It should be noted that once a welded structure develops a local leak, on-site repair is more difficult than replacing a gasket; therefore, during procurement, medium cleanliness and water quality stability should be provided to the supplier for evaluation.
Shell-and-tube heat exchangers have a mature structure and a wide pressure and temperature range, with good adaptability to media containing particles or prone to fouling, but their heat transfer area per unit volume is relatively limited, and footprint and metal consumption tend to be larger. Welded plate heat exchangers have compact plates and can achieve equivalent heat transfer in a smaller footprint in clean-medium applications such as cooling water and oil-water heat exchange. During procurement, comparison can be made from three aspects: medium cleanliness, allowable pressure drop, and installation space. When the medium contains more impurities, shell-and-tube is more reliable; when the medium is clean and space is limited, the welded plate solution is more feasible.
With welding replacing gaskets between plates, the design pressure can reach 3.0 MPa, the design temperature ranges from -40°C to 200°C, and a single-unit heat transfer area of 0.5–35 m² can cover most small and medium-sized industrial heat exchange needs. The plate channel design balances flow velocity and pressure drop and is suitable for applications where cooling water system pressure fluctuations are modest. For selection, the flow rates, inlet and outlet temperatures, and allowable pressure drop on both the hot side and cold side must be provided, based on which the supplier calculates the required number of plates and pass arrangement. Procurement personnel should confirm that the parameters come from actual operating conditions rather than estimates, to avoid excessive pressure drop caused by oversized flow margins.
First, the medium composition and corrosiveness, to specify the plate material; second, the system pressure fluctuation range—where fluctuations are large, the fatigue risk of welded joints must be assessed; third, maintenance conditions—confirm whether the site has overall lifting and replacement space; fourth, spare parts supply—understand the lead time for plates and other components. Submitting the above information together at the inquiry stage helps the supplier provide a solution matched to the operating conditions.
