FMEA
and FMECA
An Overview of Basic Concepts
and Directory of Other Resources
Failure Mode and Effects Analysis (FMEA)
and Failure Modes, Effects and Criticality Analysis
(FMECA) are methodologies designed to identify potential failure
modes for a product or process, to assess the risk associated with those
failure modes, to rank the issues in terms of importance and to identify
and carry out corrective actions to address the most serious concerns.
Although the purpose, terminology and other details can vary according
to type (e.g. Process FMEA, Design FMEA, etc.), the basic methodology
is similar for all. This document presents a brief general overview of FMEA
/ FMECA analysis techniques and requirements.
FMEA / FMECA Overview
In general, Failure Modes, Effects and Criticality Analysis (FMEA
/ FMECA) requires the identification of the following basic information:
- Item(s)
- Function(s)
- Failure(s)
- Effect(s) of Failure
- Cause(s) of Failure
- Current Control(s)
- Recommended Action(s)
- Plus other relevant details
Most analyses of this type also include some method to assess the risk
associated with the issues identified during the analysis and to prioritize
corrective actions. Two common methods include:
- Risk Priority Numbers (RPNs)
- Criticality Analysis (FMEA with Criticality Analysis = FMECA)
Published Standards and Guidelines
There are a number of published guidelines and standards for the
requirements and recommended reporting format of failure mode and
effects analyses. Some of the main published
standards for this type of analysis include SAE J1739,
AIAG FMEA-3 and MIL-STD-1629A.
In addition, many industries and companies have developed their own procedures
to meet the specific requirements of their products/processes. Figure 1
shows a sample Process FMEA in the Automotive Industry Action Group (AIAG)
FMEA-3 format. Click to enlarge
the image.
Basic Analysis Procedure for FMEA or FMECA
The basic steps for performing an Failure Mode and Effects Analysis (FMEA)
or Failure Modes, Effects and Criticality Analysis (FMECA) include:
- Assemble the team.
- Establish the ground rules.
- Gather and review relevant information.
- Identify the item(s) or process(es) to be analyzed.
- Identify the function(s), failure(s), effect(s), cause(s) and control(s)
for each item or process to be analyzed.
- Evaluate the risk associated with the issues identified by the analysis.
- Prioritize and assign corrective actions.
- Perform corrective actions and re-evaluate risk.
- Distribute, review and update the analysis, as appropriate.
Risk Evaluation Methods
A typical failure modes and effects analysis incorporates some method to
evaluate the risk associated with the potential problems identified through
the analysis. The two most common methods, Risk Priority Numbers and Criticality
Analysis, are described next.
Risk Priority Numbers
To use the Risk Priority Number (RPN) method
to assess risk, the analysis team must:
- Rate the severity of each effect
of failure.
- Rate the likelihood of occurrence
for each cause of failure.
- Rate the likelihood of prior detection
for each cause of failure (i.e. the likelihood of detecting the
problem before it reaches the end user or customer).
- Calculate the RPN by obtaining the product of the three ratings:
RPN = Severity x Occurrence x Detection
The RPN can then be used to compare issues within the analysis and to
prioritize problems for corrective action. This risk assessment method
is commonly associated with Failure Mode and Effects Analysis (FMEA).
Criticality Analysis
The MIL-STD-1629A document describes two types of criticality analysis:
quantitative and qualitative. To use the quantitative
criticality analysis method, the analysis team must:
To use the qualitative criticality analysis
method to evaluate risk and prioritize corrective actions, the analysis
team must:
- Rate the severity of the potential effects of failure.
- Rate the likelihood of occurrence for each potential failure mode.
- Compare failure modes via a Criticality Matrix, which identifies
severity on the horizontal axis and occurrence on the vertical axis.
These risk assessment methods are commonly associated with Failure
Modes, Effects and Criticality Analysis (FMECA).
Applications and Benefits
The Failure Modes, Effects and Criticality Analysis (FMEA / FMECA) procedure
is a tool that has been adapted in many different ways for many different
purposes. It can contribute to improved designs for products and processes,
resulting in higher reliability, better quality, increased safety, enhanced
customer satisfaction and reduced costs. The tool can also be used to establish
and optimize maintenance plans for repairable systems and/or contribute
to control plans and other quality assurance procedures. It provides a knowledge
base of failure mode and corrective action information that can be used
as a resource in future troubleshooting efforts and as a training tool for
new engineers. In addition, an FMEA or FMECA is often required to comply
with safety and quality requirements, such as ISO 9001, QS 9000, ISO/TS
16949, Six Sigma, FDA Good Manufacturing Practices (GMPs), Process Safety
Management Act (PSM), etc.
You can use something as simple as a paper form or an Excel spreadsheet
to record your FMEA / FMECA analyses. However, if you want to establish
consistency among your organization's FMEAs, build a "knowledge base" of
lessons learned from past FMEAs, generate other types of reports for FMEA
data (e.g. Top 10 Failure Modes by RPN, Actions by Due Date, etc.) and/or
track the progress and completion of recommended actions, you may want to
use a software tool, such as ReliaSoft's
Xfmea, to facilitate
analysis, data management and reporting for your failure modes and
effects analyses.
More information on
applications and benefits...
