In the field of industrial heat exchange equipment, gasketed plate heat exchangers and semi-welded plate heat exchangers are two widely used yet distinct devices. Although both belong to the family of plate heat exchangers, they differ significantly in structural design, sealing methods, application scenarios, and other aspects. Choosing between them requires precise matching with specific working conditions.

Structural Design and Sealing Methods: Fundamental Differences

The core feature of gasketed plate heat exchangers lies in their "gasket sealing." They consist of multiple independent metal heat exchange plates stacked together, with specially designed elastic gaskets (such as EPDM or nitrile rubber) placed between adjacent plates to achieve sealing. These gaskets fit into grooves along the edges of the plates, separating the flow channels of cold and hot fluids while preventing medium leakage. The corrugated design on the plate surfaces (such as herringbone or horizontal straight corrugations) not only increases the heat exchange area but also enhances turbulence, improving heat transfer efficiency. This structure gives the equipment strong flexibility—heat exchange area can be easily adjusted by adding or removing plates to adapt to flow changes.

Semi-welded plate heat exchangers, on the other hand, adopt a hybrid sealing structure of "welding + gaskets." They weld the edges of two adjacent plates together to form an indivisible "plate pair," while the sealing between plate pairs still relies on gaskets. The welded plate pairs form flow channels for a single medium internally, and the channels between plate pairs are separated by gaskets for another medium. This design retains part of the compactness of plate heat exchangers while enhancing the sealing performance and pressure resistance of specific channels through welding.

Application Scenarios: Selection Based on Medium Properties

The application differences between the two types of heat exchangers are mainly determined by their sealing performance and medium resistance. Gasketed plate heat exchangers are suitable for scenarios with mild, non-corrosive media, such as pasteurization of milk in food processing, water-water heat exchange in HVAC systems, and cooling of hydraulic oil in light industry. Due to the limited tolerance of gasket materials to high temperatures and strong corrosive fluids (most rubber gaskets have a long-term operating temperature not exceeding 150°C), they are more suitable for handling neutral media such as water, glycerin, and ordinary mineral oil. Additionally, their easy disassembly makes them advantageous in occasions requiring frequent cleaning, such as hygienic-grade heat exchange in the pharmaceutical industry.

Semi-welded plate heat exchangers excel in more demanding medium conditions. When one side of the fluid is corrosive (such as industrial wastewater containing acids or alkalis) or operates in high-temperature and high-pressure environments (such as solvent heating in chemical production), the welded and sealed plate pairs can prevent gaskets from direct contact with corrosive media, extending equipment life. For example, in chlor-alkali chemical industry, semi-welded heat exchangers can safely handle heat exchange between chlorine-containing circulating water and high-temperature heat transfer oil; in the energy industry, they can adapt to medium-high pressure working conditions such as steam condensation (design pressure usually up to 2.5MPa or higher).

Maintenance Costs and Flexibility: Key Considerations for Long-Term Operation

Gasketed plate heat exchangers have lower maintenance costs and simpler operation. When gaskets age or plates foul, the equipment can be directly disassembled to replace gaskets or clean plates. The replacement cost of a single set of gaskets is only 5%-10% of the total equipment cost. Their flexible modular design also allows users to adjust the number of plates at any time according to changes in production load, making upgrading and transformation easy. However, it should be noted that the service life of gaskets is significantly affected by medium temperature and pH value, requiring regular inspection and replacement under frequent start-stop conditions.

Semi-welded plate heat exchangers involve more complex maintenance. Since plate pairs are fixed by welding, individual plates cannot be replaced separately. If a local plate is damaged, the entire plate pair may need to be replaced, significantly increasing maintenance costs (the cost of replacing a set of plate pairs is approximately 3-5 times that of gasketed types). Meanwhile, their structural flexibility is weaker—adjusting heat exchange area requires replacing larger-sized plate pairs, resulting in longer transformation cycles. However, in continuously operating production lines, the reliability of welded seals can reduce unplanned downtime, indirectly lowering operational losses.

Performance Characteristics: Balancing Efficiency and Stability

In terms of heat transfer efficiency, gasketed plate heat exchangers have richer plate corrugation designs (such as fine corrugations and herringbone corrugations), leading to more significant turbulence. Their heat transfer coefficient is typically 10%-15% higher than that of semi-welded types, making them more advantageous in heat exchange of small to medium flow rates and low-viscosity media. Semi-welded plate heat exchangers, due to slightly reduced corrugation depth caused by welding processes and fixed flow channel gaps between plate pairs, have slightly lower heat transfer efficiency. However, they offer stronger anti-clogging capabilities in high-viscosity media or fluids containing small particles.

In terms of pressure resistance and sealing performance, semi-welded plate heat exchangers perform better. Welded seals can withstand higher medium pressure and temperature, while the sealing performance of gasketed types is limited by the elasticity of gaskets—their design pressure generally does not exceed 1.6MPa, and temperatures above 180°C require special gaskets (such as fluororubber), which significantly increases costs.

Conclusion: The Core Principle of Needs-Based Selection

The difference between the two heat exchangers essentially lies in the trade-off between "flexibility and tolerance": gasketed plate heat exchangers are characterized by low cost, high flexibility, and easy maintenance, making them suitable for small to medium-scale production with mild media and variable working conditions; semi-welded plate heat exchangers, leveraging the advantages of welded seals, exhibit higher reliability in harsh conditions such as corrosive, high-temperature, and high-pressure environments, making them suitable for continuous, high-load industrial scenarios. In practical selection, comprehensive evaluation of medium properties, operating parameters, maintenance needs, and long-term operating costs is essential to maximize equipment efficiency.