Failure analysis on premature perforation of multiple effect evaporators in vacuum salt making system

Multiple effect evaporators (MEEs) are extensively utilized across diverse industries, such as pulp and paper, sugar, and desalination, for the purpose of concentration and purification. Never-theless, MEEs often bring forth the issue of corrosion because of severe service conditions, thereby leading to equipment damage and decrease in efficiency. This study scrutinizes the premature perforation and corrosion of some multiple effect evaporators encountered soon after their commencement in a salt processing plant. The failed MEEs, designed to serve for 15 years, un-derwent severe corrosion and the emergence of multiple leakage points during a trial run of 40 days, with only 18 days of actual operation. To unearth the reasons for this failure, various macroscopic and microscopic analyses were carried out. The studies demonstrated that welding defects not found in time during the fabrication of evaporators reduced the corrosion resistance of the composite plate. Additionally, improper welding during the maintenance made the repair ineffective. Once the stainless-steel cladding layer was damaged, the carbon steel backing layer corroded and perforated rapidly under galvanic corrosion. Based on these findings, effective countermeasures were suggested to evade any future failures of the same kind. The outcomes of this analysis are likely to aid in enhancing the operational safety and reliability of multiple effect evaporators in vacuum salt-making systems.