Failure Modes and Effects Analysis (FMEA) - CAE Users

1 Failure Modes and Effects Analysis (FMEA)ME349 Kim MannerFMEA FMEA is a hazard Analysis tool. Overall function to identify potential component, operational or system failures and attempt to mitigate their effect (s). Process from NASA (60 s) See MIL-STD-1629A Summary: Predict what failures could occur Predict effect of failures on system function Establish steps prevent Failure or effectFMEA Failure Definition of Failure Inability to meet a customer s requirements. Component (or system) fails to perform a required Failure Failures can be categorized as: Complete Partial Intermittent Over-function Unintended functionTypes of FMEA's System -focuses on global system functions Design -focuses on components and subsystems Process -focuses on manufacturing and assembly processes Service -focuses on service functions Software -focuses on software functions Uses of FMEA Tool Develop product/process requirements that minimize failures.

2 Identify design characteristics that contribute to failures. (design them out of the system or minimize the resulting Effects ) Develop test methods and procedures to ensure that failures have been successfully eliminated. Track and manage potential risks in the design. Ensure that any failures that could occur will not injure or seriously impact the of FMEA use Improves product reliability and quality Increases customer satisfaction Early identification and elimination of potential product Failure Modes Emphasizes problem prevention Documents risks and actions taken to reduce risks Provides focus for improved testing and development FMEA Process1)Describe the product and its overall )Break overall function into separate items, parts, assemblies and identify the function of each. 3)Identify Failure Modes . A Failure mode is defined as the manner in which a component, etc. fails to meet the design Process4)Describe the Effects of those Failure )Establish a numerical ranking for the Severityof the effect .

3 Use an appropriate severity effect is defined as the effect of a Failure mode on the product/process function as perceived by the customer. 6)Identify the causes for each Failure mode. 7)For each cause, enter a Occurrencefactor. This is a numerical weight that indicates the probability of the cause occurring). Use an appropriate probability (or Occurrence) ProcessFMEA Process8)Identify Current Controls (design or process).9)Determine the likelihood of Detection. Based on the Current Controls, consider the likelihood of Detection using an appropriate Detectability tablefor Controls are the mechanisms that either:1) prevent the cause of the Failure mode from occurring or 2) detect the Failure before it reaches the Customer. FMEA Process10)Calculate the Risk Priority Number (RPN). The Risk Priority Number is the mathematical product of the numerical Severity, Occurrence, and Detectabilityratings:RPN = (Severity) x (Occurrence) x (Detectability)RPN NumberThe RPN is used to prioritize items that require additional action.

4 Items with a higher RPN are frequently addressed first. However, be aware that a high probability and low severity Failure may be less critical than a Failure with a lower probability value but a higher Suggestions List assumptions at beginning of process. List Effects of Failure in a manner that the customer would use. Limit the cause(s) of Failure to design concerns. Usually more than one cause for each Failure mode, list them all. Occurrence ratings based upon likelihood that a cause may occur; past failures, performance of similar systems or percent new parts/concepts should be considered. Preventive controls: those that reduce likelihood Failure mode or cause will occur affects occurrencevalue. Detective controls: those that find problems designed into product, assigned a detectionvalue. Detection values of 1 must eliminate potential for failureAction Results Unless Failure mode is eliminated, severity should not change.

5 Occurrence may or may not be lowered as a result of actions. Detection may or may not be lowered as a result of actions. Remedial action should detail actions and ExampleA bank performed a processFMEA on their ATM system. The following figure part of it, the function dispense cash and a few of the Failure Modes for that function. Notice that both an RPN and Criticality value is included. This is the performer s own Exampl