Failure Analysis – the Basics
Failure Analysis is the process of understanding component failure. Failures happen, often despite the best efforts of designers, engineers, and fabricators. One of the first steps to take after equipment failure should be to check similar in-service components.
Although forensic investigations may appear to look easy – they typically are not. Quite often, failures occur due a number of variables. A few variables (such as corrosion) may be evident, while others may require deeper investigation.
A multidisciplinary approach is often used to perform a root cause investigation. For a structural failure – an engineer, materials/ metallurgical professional and a welding specialist are often necessary. In addition, engaging an individual knowledgeable with the process/ factors important to the design and the performance of the equipment is strongly recommended.
An additional consideration is the potential for litigation. In such cases, legal counsel should be sought early in the process, and failed components must be preserved for examination and involvement by all parties with an interest in the matter. This is particularly important for any planned destructive testing or inspection.
Tools that are often used in a forensic investigation include: Finite Element Analysis (FEA), Computational Fluid Dynamics (CFD), Scanning Electron Microscopy (SEM) — potentially with Energy Dispersive Spectroscopy (EDS) for metallurgical assessments, and fundamental engineering principals & concepts.
In performing any type of component assessment, standardized criteria is required – including material requirements (found in Codes and Standards), Customer Specifications and other applicable documents such as Purchase Orders and Contracts.
Once a failure analysis is completed, the next step is determining how to prevent future occurrences. Such actions may include: design modifications, applying alternate materials, changes in fabrication techniques & operating parameters.
The negative aspects of a failure should not overshadow the valuable lessons that can be learned. By analyzing, understanding, and addressing the cause(s) – the engineer learns how to ensure there are no future failures.
Additionally, Root Cause Analysis (RCA) findings and their resolution(s) should be well-documented for use by peers, co-workers and future generations of engineers and designers who will inevitably ask themselves “I wonder why they did that?”
Interdisciplinary teams are essential for performing most failure analyses, since the root cause is rarely the result of a single variable. Metallurgical properties, environmental effects and stresses to a system or component are all important in determining the cause of failure.
Once we identify component failure modes, we assess remaining life, recommend inspection methods/ intervals, and modify equipment designs to reduce the likelihood of future failures.
@ O’Donnell Consulting Engineers