What is FMEA
Failure Mode & Effects Analysis (FMEA) explained with easy to understand template and examples. A complete guide with step by step approach which will help you to conduct FMEA exercise on your own. FMEA is a tool to identify and rank possible failure modes of the process and establish clear mitigation strategy associated with the risks. No matter how good a process or a design is, it is always better to anticipate the risks before hand and taking care of them helps to reduce the future failures.
Principle of FMEA
- Impact of any failure on a process is not only severity of the failure but also the frequency of occurrence & the ability of the control mechanism to detect the failure
- Analytical technique and systemized group of activities.
An interactive and never ending process
- Technique of reducing risk or of avoiding risk.
- A living document
- “Before-the-event” action; and NOT an “After-the-fact” exercise.
When to use FMEA
Case 1 :
New designs, new technology or new process. The scope of the FMEA is the complete design, technology, or process.
Case 2 :
Modifications to existing design or process (assumes there is an FMEA for the existing design or process). The scope of the FMEA should focus on the modification to design or process, possible interactions due to the modification, and field history.
Case 3 :
Use of an existing design or process in a new environment, location, or application (assumes them is an FMEA for the existing design or process). The scope of the FMEA is the impact of the new environment or location on the existing design or process.
Types of FMEA
All potential problems that may result in Safety hazards, Malfunctioning and shortened product life or must be solved in the product design. The question How can the product/service design aspects fail to do what they are designed for is focussed here.
All potential problems that may result in Safety hazards, defects in product/service production process and reduced process efficiency. The question “How can people, materials, equipment, methods, and environment cause process failures is focussed here.
FMEA Flow and Definitions
|Characteristics||Purpose of the product or Process|
|Failure Mode||How can the product / process fail to
|Effects||Which effects are most severe to customer?|
|Causes||Which causes are most likely to occur?|
|Controls||Ability for current controls to detect causes?|
|RPN||Which high risk cause we work on first?|
|Action Plan||Recommended actions & responsibilities|
|Severity, Occurrence & Detectability are Measured/rated on a scale of 1-10|
Step 1 FMEA Number : This should be a log controlled number for tracking the document.
Step 2 Part number/process step : FMEA can be done for a particular part or a process. While doing it for a process, we need to do for each step in that process. This needs to be captured in the 1st column of FMEA sheet.
Step 3 Potential Failure Mode : Now the critical steps will start and first we need to understand what is potential failure mode for a process step or a part:
- How can the process / task fail to meet specification ?
- What would a customer consider as failure/rejection? (End User, Subsequent operation, Service)
- Manner in which process could potentially fail to meet the process requirements and / or client’s intent
Step 4 Potential causes of failure : Describe in terms of something that can be corrected or controlled. Be specific. Try identify the causes that directly impact the failure mode, i.e., root causes.
Step 5 Potential Effects of failure : Describe effects of failure in terms of what customer(s) might notice or experience, customer here could be the subsequent operations. We can understand this with an example – suppose there is a failure mode in terms of leak from a clamp, the effect could be wet floor.
Step 6 Current control : In this step capture current controls to prevent or detect the failure mode, based on this we have to assign the Detection rating.
Severity (S): Severity rating is the effect of the failure on the rest of the system if the failure occurs. These values are often indexed from 1 to 10 (Low to high severity). A value of 1 means the user will be unlikely to notice and with a 10 meaning that the safety of the user is in jeopardy.
**Important Note : Once we bring in more controls the occurrence will reduce and Detection rating will also improve but Severity rating will remain the same.
Occurrence (O) : Values for this index generally index from 1 to 10 with 1 being virtually no chance and 10 being near certainty of occurrence. Only occurrence resulting in failure mode to be considered and If available please use statistical data to determine occurrence ranking.
Detection (D): D is the measure of the effectiveness of the current controls in place to identify the potential weakness or failure prior to release to production. This index may also range from 1 to 10. A value of 1 means this will certainly be caught whereas a value of 10 indicates the design weakness would certainly make it to the production without detection.
Calculation of RPN
Risk Priority Number (RPN): Once you have given ratings to “S”, “O” and “D” then it is very easy to calculate RPN for that particular row item(part/process step).
RPN = S*O*D
Now identify Failure modes with highest RPN values, next step would be to review and update the current control plan so that risks go down. This will help you to reduce Occurrence and improve Detection.
Things to remember:
- Once we bring in more controls the occurrence will reduce and Detection rating will also improve but Severity rating will remain the same.
- Use the RPN to prioritize your failure modes. Higher RPNs require immediate focus & a good control plan (use mistake proofing if possible !!).
- The RPN will highlight the biggest risk areas in your current process. Once you improve the process, update your Process Map and FMEA.
- Have you reduced the risk? Revisit the FMEA document regularly. So, FMEA is a living document.
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