What is FMEA and how it works ?

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As per “Practice Standard of Project Risk Management” , FMEA is a technique which can be used in Identify Risk Process and also further as analysis tool during Perform Quantitative Risk Analysis process.

What is FMEA?

Failure Mode and Effects Analysis (FMEA) , also called Fault Tree Analysis is a design tool for assessing risk associated with the different ways (modes) in which a part or system can fail, identifies the effects of those failures, and provides a structure for revising the design to mitigate risk where necessary.

An FMEA is an engineering analysis done by a cross-functional team of subject matter experts that thoroughly analyzes product designs or manufacturing processes early in the product development process, finds and corrects weaknesses before the product gets into the hands of the customer.

An FMEA should be the guide to the development of a complete set of actions that will reduce risk associated with the system, subsystem, and component or manufacturing/assembly process to an acceptable level.

If effectively used throughout the product life cycle, it will result in significant improvements to reliability, safety, quality, delivery, and cost.

Types of FMEAs :

The primary objective of an FMEA is to improve the design. The three most common types of FMEAs are:

  • System FMEA, the objective is to improve the design of the system.
  • Design FMEA, the objective is to improve the design of the subsystem or component.
  • Process FMEA, the objective is to improve the design of the manufacturing process.

Basic Terms used in FMEA:

  • “Function”: What task the item is intended to perform, usually to a given standard of performance.
  • “Failure Mode”: The way the part or assembly could fail to meet requirements.
  • “Effect “: The consequence of the failure on the next higher subsystem, system, or user.
  • “Cause “: The reason for the failure, preferably found by asking “why” until the root cause is determined.
  • “Control: The method or action currently in place to reduce risk.
  • “Severity” : Ranking number associated with the most serious effect for a given failure mode .
  • “Occurrence” is a ranking number associated with the likelihood that the failure mode and its associated cause will be present in the item being analyzed.
  • “Detection” is a ranking number associated with the best control from the list of detection-type controls, based on the criteria from the detection scale.
  • “Risk Priority Number (RPN)”: A numerical ranking of the risk of each potential failure mode, which is comprised of three elements: severity of the effect, occurrence of the cause, and detection of the cause.
  • Recommended Actions: The specific action steps that will be implemented to reduce risk to an acceptable level.

Steps to be followed :

Step 1 : Detect a Failure mode :For each item that will be analyzed, identify its functions, failures, effects, causes, and current controls. Use engineering and business judgment to select the issues that will be considered in the analysis.

Step 2: Assign Severity Number (S): Rate the severity of the effect on the appropriate severity scale.

Step 3: Assign Probability of occurrence (O): Rate the likelihood of occurrence of the cause on the appropriate occurrence scale.

Step 4 : Assign Detection Number (D): Rate the likelihood of detection of the cause (based on current controls) on the appropriate detection scale.

Step 5 : Assign Risk Priority Number (RPN ) : Multiply the three rankings (S*O*D) together to get the risk priority number (RPN) for each failure mode being considered.

Step 6 : Action Taken : Develop effective recommended actions /or carry out corrective actions to address most serious concerns based on RPN score.

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Template can look like below :

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Conclusion :

FMEA helps us categorize failures, identify it and then sort out which failure modes need attention in the design process and verifies that our design process has actually made things better .It is a very useful tool, it’s very easy to use and it’s great for documentation .It is highly recommend to use this tool wherever possible in the design process to help for informed decision-making and it gives you a really good picture where you might encounter failure.

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