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Corrosion
Corrosion challenges across heat exchanger configurations
Shell and tube heat exchanger cleaning .
Heat exchangers are critical components in various industries , facilitating the transfer of heat between two mediums while keeping them physically separated . However , the efficient operation of heat exchangers is often hampered by corrosion , which can lead to decreased performance , increased maintenance costs , and even system failure if not properly addressed . In this article , we will explore the corrosion challenges faced in different heat exchanger designs — plate heat exchangers , shell-andtube exchangers , and finned tube exchangers — and discuss customized corrosion protection strategies tailored to each configuration .
By Omari Hussein Sabuni , Mechanical Engineer , Kinyerezi Power Plant
Plate heat exchangers Plate heat exchangers are characterized by their compact design and high heat transfer efficiency , making them popular in HVAC , refrigeration , and food processing industries . However , they are susceptible to various forms of corrosion , including pitting , crevice corrosion , and galvanic corrosion .
Pitting corrosion Plate heat exchangers , with their closely spaced plates , are susceptible to pitting corrosion , a localized form of corrosion that leads to the formation of small , often deep pits on the metal surface . This corrosion type is particularly concerning in environments where chloride ions are present in the process fluid , as they can significantly accelerate the corrosion process . Pitting corrosion initiates
at microscopic defects on the metal surface and can progress rapidly , compromising the structural integrity of the plates . Mitigation strategies :
• Material selection : choosing materials with high corrosion resistance , such as stainless steel or titanium , can greatly mitigate the risk of pitting corrosion .
• Surface finish : employing smooth surface finishes and proper fabrication techniques can minimize the initiation points for pitting corrosion , enhancing the overall corrosion resistance of the plates .
• Monitoring and inspection : regular inspection using non-destructive testing methods is essential to detect early signs of pitting . This allows for timely maintenance and replacement of affected plates .
Crevice corrosion Crevice corrosion is another concern in plate heat exchangers , occurring in narrow gaps or crevices between adjacent plates . These spaces provide an ideal environment for stagnant fluid , leading to the accumulation of corrosive substances and promoting localized corrosion . Proper gasket selection and installation are crucial factors in preventing crevice corrosion . Mitigation strategies :
• Gasket selection : choosing gaskets made from materials resistant to corrosion is essential . Elastomers or non-metallic gaskets may be
44 Heat Exchanger World December 2024 www . heat-exchanger-world . com