In brief
FMEA (failure mode and effects analysis) is a preventive method for systematically assessing the potential failures of a product or process.
Contents
What is FMEA?
FMEA analyses how a component, an assembly or a process step can fail, what consequences this has and which causes lie behind it. The aim is to identify risks before failures occur and to derive countermeasures. The general procedure is described in the international standard IEC 60812. The main distinction is between product or design FMEA and process FMEA.
An interdisciplinary team considers the failure mode, failure effect and failure cause for each element. Traditionally, the severity of the effect, the probability of occurrence and the probability of detection are each rated on a scale; their product gives the risk priority number (RPN). Other approaches prioritise using rating tables, because the RPN can make very different risks numerically equal. The result is a set of actions for prevention or better detection, with owners and deadlines.
In maintenance, FMEA is used to identify the critical components of a plant, for example as part of reliability-centred maintenance. This yields maintenance tasks, inspection intervals and the question of which spare parts should be held in stock. The FMECA variant extends the analysis with an explicit assessment of criticality.
In practice: maintenance and procurement
For spare parts planning, a cross-check is worthwhile: components with severe failure effects and long replacement lead times belong on the list of critical spare parts. Failure data from the maintenance history improves the rating of the probability of occurrence.
Synonyms and abbreviations: failure mode and effects analysis · FMECA · process FMEA (PFMEA) · design FMEA (DFMEA)
Frequently asked questions
What is the difference between product FMEA and process FMEA?
Product or design FMEA examines how a component or system can fail because of its design, for example due to unsuitable materials or tolerances. Process FMEA looks at the manufacturing or assembly steps and asks where failures can arise there. Both use the same methodology but start at different points.
How is the risk priority number (RPN) calculated?
The RPN is the product of three ratings: severity of the failure effect, probability of occurrence and probability that the failure is detected before it has an effect. Each factor is usually rated on a scale of 1 to 10. A high RPN indicates a need for action but should not be the sole deciding factor, as severe effects always deserve attention.
How is FMEA used in maintenance?
Maintenance teams use it to analyse which components of a plant can fail, in what way, and how serious the consequences are for safety, production and the environment. From this, servicing and inspection tasks, inspection intervals and stocking decisions for spare parts are derived. FMEA is often a building block of reliability-centred maintenance.