Digital image correlation for gasketed plate heat exchangers structural health monitoring

Gasketed plate heat exchangers (GPHEs) operating under severe pressure fluctuations are susceptible to cyclic structural displacements, gasket loosening, and leakage failures, particularly under inadequate tightening conditions. Despite the relevance of these phenomena to equipment integrity and operational safety, non-intrusive methodologies capable of monitoring distributed structural displacements in GPHEs under operating conditions remain limited. In this study, a low-cost videometry approach based on Directional Digital Image Correlation (D-DIC) and optical flow was experimentally investigated as a non-intrusive Structural Health Monitoring (SHM) methodology for leakage precursor identification in GPHEs. Hydrostatic and hydrodynamic tests were performed using a 31-plate AISI 316L GPHE instrumented with Linear Variable Differential Transformers (LVDTs) for validation purposes. The proposed methodology successfully captured distributed displacement fields associated with the breathing effect and pressure cycling. The optical measurements showed good agreement with LVDT data, with mean absolute errors of approximately 0.064 mm in hydrostatic tests and 0.016 mm in hydrodynamic tests, together with high temporal synchronization between signals. The results also demonstrated that relatively small tightening variations significantly increased cyclic displacement amplitudes, indicating strong coupling between structural flexibility and hydraulic operation. Furthermore, displacement concentration regions observed immediately before leakage events revealed structural patterns associated with leakage initiation. The findings demonstrate the potential of low-cost non-contact videometry for continuous SHM and early leakage precursor identification in industrial GPHE systems.