FAILURE MODE EFFECT ANALYSIS

November 16, 2013


The following discussion on failure mode effect analysis was published through PDHonline.org and written by this author.  In the “world of reliability engineering” this process is extremely valuable in determining those components and sub-assemblies that may fail and may fail early in their life.  This one is a little “off the wall” but hope you enjoy it anyway.

Failure Mode and Effect Analysis is the cornerstone of the reliability engineering process. It is a methodology for analyzing potential reliability problems early in the development cycle.   It is a technique to identify potential failure modes, determine their effect on the operation of the product and identify actions to mitigate the failures.   With this being the case, an engineer can “design out” components or modify those components to make them more robust relative to the operational conditions that will be encountered during use.  Please note that FMEAs are always conducted after critical subassemblies are identified.  There are several types of FMEAs, as follows:

  • 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

We look at, and rate, three areas: severity, probability of occurrence and the ability to detect the specific failure.  There is a very simple template that will capture the possible failure modes and designate actions to be taken at a later date.  An example of that template is as follows:

FMEA Template

 

The “header” for the template would show the Product Name, the Date, the System or Subsystem Name, the Name of the Design Leader and the Revision Number.

The process of conducting a FMEA for any product is as follows:

  1. Assemble a team of individuals who have product knowledge.  These people should come from the following disciplines: a.) design engineering, b.) manufacturing, c.) service, d.) quality, e.) repair.
  2. Make sure the  Failure Block Diagrams (FBDs)  and “P”-Diagrams are available to adequately represent the system, subsystem or component.
  3. Construct the FMEA template or work sheet.
  4. Convene the team to identify the possible failure modes and assign importance to the severity, probability of occurrence and the probability of detecting the failure. Generally, the rating system goes from one (1) to ten (10) with ten being the most severe and creating the greatest operational issues.  A recommendation from Mr. Stephen Curtis posted on the Six Sigma.com web site recommends the following classifications for the three- line items:
  5. CATEGORIESMultiply the assigned numbers for severity, occurrence and detection together for a final score and record that score for later use.  A score of 1,000 would indicate a failure that should definitely be addressed and one that would be coded as a “red” item.  Red items must be fixed before pre-pilot builds occur and certainly before pilot runs occur.  Some companies designate any score above 600 as a “red” item.
  6. For each failure mode, identify what you feel to be the “root cause” of the failure.  This will take experience and you may wish to consult the services of field technicians for their comments relative to product use and problem areas.
  7. Describe the effects of those failure modes; i.e. injury to user, interoperability of product, improper appearance of product, degraded performance, noise, etc.
  8. Determine what must be the initial recommended action.  This is done for each failure mode.
  9. Assign responsibility for addressing the “fix”.
  10. Assign a “get well” date
  11. .Before adjourning, establish a time to reconvene for a status on the failures and the “fixes”.Before adjourning, establish a time to reconvene for a status on the failures and the “fixes”.

This is a marvelous tool for reliability practitioners and engineers of all “stripes”.  One used by  manufacturers and designers in every branch of engineering and technology.  Hope you enjoy this one.

 

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One Response to “FAILURE MODE EFFECT ANALYSIS”

  1. Suzanna Says:

    I spent a great deal of time to find something like this

    Like


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