Failure Mode and Effects Analysis
What is FMEA?
Failure Mode and Effects Analysis (FMEA) is a process that is available to organizations to identify potential failures with assets and other areas of business. FMEA is a powerful tool that combines the experience and wisdom of all stakeholders.
Benefits from FMEA include a reduction in potential failures and the savings of lives and excessive costs. Organizations can discover the steps necessary to prevent catastrophes with the application of valuable resources to the appropriate need.
Many organizations are required to demonstrate completion of an FMEA or other risk assessment analysis. FMEAs can guide maintenance and reliability team’s most effective efforts.
How to use FMEA
Maintenance and reliability teams use FMEA to answer technical and complicated questions. They can also use FMEA to understand and address issues when technical solutions border the needs of the larger organization. A mechanical design that does not address the needs of users is doomed to failure.
The weighted decision criteria of FMEA provides a clearer path for all interested parties. The final value is a risk and is referred to as a Risk Priority Number (RPN). The RPN indicates the steps a team should or should not take to detect or mitigate failures.
Financial savings vs safety
An example of an equipment design issue that requires production and other department input is engineering for ease of changeover process. Easier and faster changeover processes can improve a company’s bottom line.
A quicker and easier process can also introduce potential problems related to safety (equipment that is not firmly affixed) or equipment reliability (loose apparatus vibrates and damages equipment).
FMEA balances the needs to resolve safety and quality solutions with cost-cutting opportunities.
Organizations can select a systematic method that best fits their needs. These processes provide detailed instructions regarding the items requiring consideration. Approved procedures will define the weight of each decision and how an RPN is determined.
Various industry organizations promote a process that fits is members needs. It is essential to select the components that best meet the solutions sought. The difficulty could be in choosing the right expert and process.
Caterpillar’s Brazil unit used an FMEA to determine that the assembly process used to build its generator sets created 43 ergonomic risks of the 88 assembly steps they followed. Caterpillar pursued 17 steps that required immediate mitigation of the risks. These steps included building a special cart to place the components in a position that did not require employees to bend or stoop. Even the shop floor was rearranged to deliver parts via a conveyor with improved employee access.
What are failure modes?
A failure mode is a description of the way that a component or process can fail.
One of five failure modes can occur:
- Full function failure
- Partial/degraded function failure
- Intermittent function failure
- Over function failure
- Unintended function failure
Examples of typical equipment failure modes are corrosion, mechanical breakdown, electrical short or open, torque fatigue, deformation, and cracking.
What are effects?
An Effect is a description of the consequences of each failure. Effects are assigned a numeric value corresponding to the failure’s impact. Failure effects range in severity from severe (death) to nuisance failures. Numeric values clarify a failure’s expected impact on the organization.
Components of FMEA
Likelihood of failure
The likelihood of failure is the probability score provided by the FMEA team. A range from 1 to 10 defines the probability of an event occurring. A score of one indicates a failure will not likely happen. A score of 10 means that a failure will likely occur.
Some of the likelihood probability scoring choices are:
- An unlikely probability of occurrence
- A remote probability of occurrence
- An occasional probability of occurrence
- A moderate probability of occurrence
- A high probability of occurrence
Organizational teams will need to determine the criteria that define each probability value.
Detectability is the final component of the FMEA equation. The weighted scale can run from a high degree of detectability to a low degree of detectability. The importance of the ability to detect a fault risk becomes less or more important based on the effects score.
Examples of detectability can range from the ability to determine if a machine is running (highly detectable) to whether the quality of medicine produced is correct (low). A well-run quality management program will overcome a low detectability component.
A well-run quality management program is a risk control tool that manages the risk determined through FMEA. The RPN drives the organization's risk control efforts.
Equipment failure that has a low RPN only poses a small threat to the organization’s success. Equipment with a high RPN receives elevated attention and effort due to its threat to the organization’s goals.
Steps available for equipment or processes with a high RPN include:
- Using continuous monitoring
- Using advanced monitoring or detection technologies
- Using predictive maintenance
- Using a higher amount of human inspectors
- Implementing rapid replacement plans in the event of a catastrophic failure
FMEA is a powerful tool that has a large set of experts and resources for any size organization. Many maintenance programs and companies are required to demonstrate that an FMEA or other risk assessment is conducted for their critical components or processes.
Working from an FMEA empowers maintenance planners and schedulers. It gives them a numeric indicator of what is most important to their organization.