Coupling Failure for Torsional Fatigue: A Multi-Disciplinary Root Cause Analysis Approach

Abstract

The successful growth of an EHS culture, focus on equipment availability and reliability, as well as continuous pressure on increased production is causing a higher demand for improvements in Root Cause Analysis (RCA) quality and speed of completion. Root causes investigations need to be driven to a strong level of understanding and resolution to guarantee safe operation, to optimize production and to reduce costs. RCA processes are many times based on different disciplines to investigate the most challenging failures having the following characteristics: - Top Critical: potential impact on safety and production; - First occurrence: no similar cases investigated before; - Lack of information: no operation data and only fragmented information available. In these cases only a multi disciplinary approach allows studying various aspects of the failure and validating the results as an overall system solution. In this paper the authors present a recent study where finite element stress model calculations, metallurgical laboratory analysis (fractography examination, mechanical testing, fracture mechanics), dynamic analysis, fatigue tests and field measurements were used to investigate causes of coupling failure and determinate corrective actions. Results of each study are presented with special focus on comparative analysis and data matching.