Failure Modes and Effect Analysis

Anticipation … The Future Of Quality Management

 

Failure Mode and Effect Analysis (FMEA) is a way of looking at something to question whether or not it will ever fail … and then studying the consequences of those potential various failures to determine the severity to the customer.  It examines potential failures in systems, designs, and processes for your products/services.

FMEA is one of the first structured, systematic techniques for failure analysis.  It was developed by reliability engineers to study problems that might arise from malfunctions of military systems. An FMEA involves reviewing as many components, assemblies, and subsystems as possible to identify failure modes, and their causes and effects.  FMEA’s help identify potential failure modes based on experience with similar products and processes—or based on common physics of failure logic. It is widely used in development and manufacturing industries in various phases of the product life cycle.  Effects analysis refers to studying the consequences of those failures on different system levels.

 

Murphy said it best when he said, “Anything that can possibly go wrong, does.”

 

FMEA’s prioritize risk factors such as occurrence (O), severity (S), and detection (D) that are usually summarized as a Risk Priority Number (RPN).  Traditionally, RPN approaches have shortcomings in setting the weight of risk factors.  It is important to consider the individual indicators on their own and their weights of risk given by experts.

A Critical System (Safety or Life) is a system whose failure or malfunction may result in one (or more) of the following outcomes:

  • death or serious injury to people
  • loss or sever damage to equipment/property
  • environmental harm

Critical related systems comprise of everything (hardware, software, infrastructure, and the human aspects) needed and related to perform one or more functions, in which failure would cause a significant increase in risk for people, property, products and/or services involved.  Critical systems are those that do not have full responsibility for controlling hazards and/or environments such as loss of life, severe injury or severe environmental damage.  The severity, occurrence, and detection of a failure becomes hazardous in conjunction with the failure of other systems or human error.

Risks of these sort are usually managed with the methods and tools of design, engineering, process and quality management.  A critical system is designed to loose less than one life per billion hours of operation (one occurrence every 500,000 years).  Typical process design methods include Failure Mode Effect Analysis (FMEA) and Fault Tree Analysis (FTA).  Global Planning Group’s mandate is to help you … Anticipate The Future   Because most of the time you may pick two of the following three … but not more:

  1. It can be designed correctly
  2. It can be built quickly
  3. It can be operated cheaply

 

Why Global Planning Group?

  • Focus on Prevention
  • Correct Procedures
  • Lessons Learned
  • Trained Team
  • Skilled Facilitation
  • Leadership Support
  • Anticipate The Future

 

Failure Mode Effect Analysis (FMEA) and Failure Modes Effect and Critical 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 – PFMEA, Design FMEA – DFMEA, System FMEA, Product FMEA, FMECA, etc.), the basic methodology is similar for all. ReliaSoft’s Xfmea software facilitates data analysis and reporting for FMEAS, with configurable settings and predefined profiles for the major published standards.

 

FMEA / FMECA Overview

In general, Failure Mode Effect (and Criticality) Analysis 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)

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:

  1. Risk Priority Numbers (RPNs)
  2. 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-4 and MIL-STD-1629A. In addition, many industries and companies have developed their own procedures to meet the specific requirements of their products/processes.

 

Basic Analysis Procedure for FMEA or FMECA

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)

Evaluate the risk

  • 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.

Criticality Analysis
The MIL-STD-1629A document describes two types of criticality analysis: qualitative and quantitative.

To use qualitative criticality analysis to evaluate risk and prioritize corrective actions, the analysis team must a) rate the severity of the potential effects of failure and b) rate the likelihood of occurrence for each potential failure mode. It is then possible to compare failure modes via a Criticality Matrix, which identifies severity on the horizontal axis and occurrence on the vertical axis.

To use quantitative criticality analysis, the analysis team considers the reliability/unreliability for each item at a given operating time and identifies the portion of the item’s unreliability that can be attributed to each potential failure mode. For each failure mode, they also rate the probability that it will result in system failure. The team then uses these factors to calculate a quantitative criticality value for each potential failure and for each item.

 

Applications and Benefits for FMEA and FMECA

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 and/or track the progress and completion of recommended actions, you may want to use a software tool, such as RCM, to facilitate analysis, data management and reporting for your failure modes and effects analyses.