Modal Analysis for HVAC Fan Failure Resolution

This technical report presents a detailed investigation into recurring failures of two belt-driven HVAC fan units used for ventilation on an offshore gas production platform. The investigation was initiated due to excessive vibration causing operational disruptions and high maintenance costs. AVT Reliability's Asset Integrity Division conducted a comprehensive analysis, employing Operational Deflection Shape (ODS) testing and Modal testing to identify the root cause of the failures. The assessment involved over 70 vibration measurement locations and the creation of animated 3D models to visualize the vibration behavior. The findings indicated that resonance during normal operation was leading to excessive vibration and component movement. To address this, several design modifications were evaluated, resulting in an engineered solution that increased the system's natural frequencies, thereby reducing the risk of resonance. The report concludes with plans for validation testing post-modification to ensure the effectiveness of the implemented solutions.