What Is FMECA (Failure Mode, Effects, and Critical Analysis)?
May 9, 2023
FMECA (Failure Mode, Effects, and Critical Analysis) helps identify potential failures in your systems. It’s an extension of the FMEA (Failure Mode and Effects Analysis)—FMECA also factors in criticality analysis, which is a systematic approach to applying a criticality rating to equipment and assets based on potential risks.
Senseye’s whitepaper, The True Cost of Downtime, found that the annual cost of downtime averages $129 million per facility. So even if you’re not in that bad a position, you can imagine how significantly failure-induced downtime can contribute to your expenses.
In this article, you’ll learn what FMECA is and how to plan, track, and optimize maintenance at your facility.
What Is FMECA?
FMECA is a risk assessment methodology in which you determine failure modes, assess their level of risk to your equipment or system, and rate the failure based on that level of risk. The U.S. military invented this FMECA analysis technique in the ‘40s. The military continues to use the FMECA even today under the MIL STD-1629A.
FMECA is a commonly used technique for performing failure detection and criticality analysis on systems to improve their performance. In addition, it typically provides input for Maintainability Analysis and Logistics Support Analysis, both of which rely on FMECA data. With Industry 4.0, many industries are adopting a predictive maintenance strategy for their equipment. To prioritize failure modes and identify mechanical system and subsystem issues for predictive maintenance, FMECA is a widely used tool.
Once you have a list of failure modes in order of priority, you can implement preventive strategies to mitigate those risks. Of course, the process isn’t full-proof—it doesn’t guarantee zero failures. Some level of failure risk will persist, and you or your team will make mistakes at some point, but FMECA helps minimize the probability and costs of failure for the business.
FMECA is predominantly used in space and military applications, but manufacturers can practically use it in almost any industry.
FMECA vs. FMEA
Performing FMECA instead of FMEA is based on the desire to achieve a more quantitative approach to risk determination. In contrast, FMEA relies on a multi-functional team to set Severity and Occurrence using guidelines. The FMECA process involves completing an FMEA process worksheet, followed by a Criticality Worksheet to determine criticality. FMEA focuses on qualitative information where you explore what-if scenarios. It assesses the failure modes and their effects.
FMEA becomes FMECA with the addition of critical analysis, which allows the FMEA team to identify those failure points that are critical along with the probability that failure will occur. FMECA goes a step further and assesses the criticality of failure modes and ranks them based on priority (or level of criticality).
When you have component data, using FMECA makes more sense because it lets you focus on the criticality of failure modes. However, if component data is unavailable, use FMEA.
Once you’re through these eight steps, continue with the next set of steps to perform FMECA.
The FMECA Process
The FMECA process is essentially the same as the FMEA process, except that FMECA also includes criticality analysis. We explain the FMEA process in depth in our FMEA guide, but here’s a quick overview:
- Step 1 – Assemble the FMEA team: Put the production engineer or maintenance manager in charge of the team and invite team members from across relevant roles like design engineers, process designers, and marketers.
- Step 2 – Gather data: Start by determining the type of FMEA you’ll use to gather data. Will you use design FMEA (things like material properties and geometry), process FMEA (things like processing methods and maintenance schedules), or functional FMEA (the overall workflow)? Next, you need resources like block diagrams, tree diagrams, and other resources to make the analysis easier.
- Step 3 – Define the scope: List the systems, subsystems, assemblies, and the relationship between parts that the FMEA team will evaluate and set up standard operating procedures to streamline the process.
- Step 4 – Identify potential failure modes: List the things that could go wrong (failure modes) using maintenance history, frontline employee knowledge, and other resources.
- Step 5 – Determine severity rankings: A severity ranking of one to 10 is assigned based on the failure mode’s severity. The rating isn’t a computed number but a rating based on judgment.
- Step 6 – Determine occurrence rankings: The occurrence rating is a proxy for the probability of occurrence of a failure mode (again, on a scale of one to 10).
- Step 7 – Determine detection rankings: The detection rating, assigned on a scale of one to 10, communicates how easy it is to identify failure before it occurs.
- Step 8 – Calculate RPN and prioritize actions: Multiply severity, occurrence, and detection rankings to calculate a risk priority number (RPN). Each element—severity, occurrence, detection—should be assigned a value on a 1 (best) to 10 (worst) scale. The cumulative effect of each failure element is what’s called a Risk Priority Number (RPN). Multiply your three elements to arrive at the RPN:
Risk Priority Number (RPN) = Severity x Occurrence x Detection.
The FMECA Steps
Step 1: Determine the Approach
Before thinking about failure mode criticality, you need to determine the approach. Here are the two approaches you can select from:
- Top-down approach (functional method): The functional method is typically used during the product or process design phases. For example, when you’re designing a budget bathroom rack, what potential failures are likely to occur? The end-user might overload the rack and break it. Using stronger material and designing it to prevent overload can help avoid this failure.
- Bottom-up approach: The bottom-up approach involves starting with the components and then viewing them in the context of more extensive systems. For example, when manufacturing a rack, you can identify the possible failures that could occur because of the rack’s handle. Is the handle too fragile? Can you use a different material to increase strength?
Step 2: Determine the Type of Analysis
Once you’ve picked an approach, you need to select the type of analysis:
Qualitative analysis is excellent when you don’t have enough component data. It’s a great what-if analysis tool in the early phases, like during the design process. For qualitative analysis, you’ll need a severity ranking.
The conventions differ among industries, but here’s a great example from the Automotive Industry Action Group of ratings you can use based on the degree of impact of a failure mode:
Similarly, here’s an example of the occurrence rating where you rank failure modes based on failure rate.
If you’ve compiled data, it’s best to use quantitative analysis. Unlike qualitative analysis, quantitative analysis is more concrete because it builds on existing data. With historical data, you can use more accurate inputs for mathematical formulas used during the analysis.
The math is a little complex to get into here, but the Reliability Analysis Center (RAC) has a great resource that explains quantitative analysis in FMECA.
The criticality number you get using the formula above represents the frequency of a failure node occurring. So it’s a number that quantifies and bakes in the consequences of failure by summing up all failure criticality numbers.
Once you have this number, you’ll need to adjust it for any redundancies that may have been introduced. Redundancy is created when you identify potential failures during the FMEA process and take corrective action. This means you’ve provided more than one way to correct a failure. Unfortunately, the math for factoring in redundancies is too technical, but RAC’s guide offers a great explanation.
Step 3: Create a Criticality Matrix
The criticality matrix summarizes your FMCEA. It’s a matrix with severity on the X-axis and probability on the Y-axis. So low-severity, less probable failure modes appear at the bottom right, while the most severe, highly probable ones appear at the top left.
Step 4: Take Action
Once you identify the potential failures you must focus on based on the severity level, you can start thinking about failure causes and corrective actions to minimize the probability of component failure. For example, you can create redundancies to make your systems more resilient or modify the design to reduce the possibility of critical failure.
Every time you take corrective action, you must recompute and rearrange the criticality matrix. Continue the process for as long as you minimize failure mode effects.
Execute Corrective Actions Effectively with a CMMS
Say you’re through with the failure analysis. You’ve come up with a list of critical items you need to work on to minimize the effects of failure. How do you execute these actions effectively?
A computerized maintenance management system (CMMS) like MaintainX ensures you have complete visibility over work orders. MaintainX also helps with complete maintenance planning, allowing you to schedule work orders for corrective actions that involve maintenance.
Everything you do in MaintainX lives on the cloud, making it remotely accessible. In addition, MaintainX automatically creates an audit trail for all actions, saving you and the team plenty of time.