Failure Analysis – The Basics
Failure Analysis is the Process of Understanding the Root Cause of Materials / Equipment Failure. One of the first steps to take after equipment damage / failure should be to check similar in-service components.
Damage may consist of permanent structural deformations (plastic strains), local damage (cracks), or in general any deterioration of the structure, or lack of functionality. It should be noted that damage onset does not mean the final or catastrophic failure of the structure. Often, there is a progression of damage before complete failure occurs. Residual strength is the term for the remaining capability of the damaged structure to withstand loads. It is common to refer the concept of damage tolerance for a structure in presence of undetected damages – produced by manufacturing defects, fatigue, ambient conditions, or accidental, is still able to withstand the loads produced during its service life.
Although failure 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.
An interdisciplinary 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 expert who is knowledgeable with specific 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. In addition, failed components must be preserved for examination. This is particularly important for any planned 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, and 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?”
The negative aspects of a failure should not overshadow the valuable lessons that can be learned.
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.
Our interdisciplinary approach helps our clients identify, mitigate, and correct vulnerabilities and risks throughout each stage of the product lifecycle to improve product safety and performance.
O’Donnell Consulting Engineers Performs Failure Analysis – and Subsequently Redesigns Equipment to Reduce the Likelihood of Future Failures. This includes Tanks, Piping, Valves, Vessels, Cyclones, Conveyors, Dryers, Mixers, Pumps and Welded Assemblies.
@ O’Donnell Consulting Engineers
