FMEA:  Failure Mode and Effect Analysis

 

Description:

Failure Modes and Effects Analysis is a tool used by managers to
identify and analyse potential failure risks within the systems. The FMEA
process begins by identifying “failure modes,” the ways in which a product,
service or process could fail. Team may examine every element
of a service, starting from the inputs till the output is delivered to the
customer. It is a framework for analysing the design of a product or service
system to identify potential failures, then taking steps to counteract or at
least minimize the risks from those failures. These risks are classified according
to probability of occurrence and impact/ severity, based on experience. The
objective of FMEA is to remove ‘identified’ failures out of the system, ideally
with minimum cost, time and effort. It seeks to reduce risk at all levels starting
with most important actions to decrease or limit either impact or probability
of occurrence of event. (Figure 1)

Utility:

·      
Utility of the tool is in ensuring
that any possible disastrous situation is prevented or at the very least, its
effect is minimized and there is a mitigation plan in plan to counter.

·      
New
or existing processes being designed or changed

·      
Carry-over processes for use in new
applications or new environments.

 

Procedure
to follow:

Process
steps in FMEA:

1.     
Identify
potential failures and effects

2.     
Determine
severity

3.     
Measure likelihood
of occurrence

4.     
Failure detection

5.     
Generate a Risk Priority
Number

Step 1:
Identify potential failures and effects

Analyse functional requirements and their
effects to identify all failure modes such as fracture. Failure modes in one
component can induce problems in others. We need to detect their failure effects.
An example could be user injury.

Step 2:
Determine severity

Severity is the seriousness of failure
consequences of failure effects. Usually, it is rated on a scale of 1 to 10,
with 1 being lowest severity and 10 being hazardous. (Figure 2)

Step 3:
Measure likelihood of occurrence

Examine how often each failure occurs. Observe
similar procedures and processes and their documented failure modes. All
potential failure causes should be documented in technical terms. An example of
a failure cause could be misplaced machinery etc. Again, the ranking is done
from 1 to 10, with 10 as extremely likely. (Figure 3)

Step 4:
Failure Detection

After mitigation plan is devised, it is tested
for efficacy and efficiency. Inspection is needed, and techniques are
determined that detect failures. These are assigned a detection value, which
indicate how likely it is to detect failures. Higher values imply that the
failure might not be detected in the system. (Figure 4)

Step 5:
Generate RPN

All failures are not the same and FMEA
prioritizes them according to:

Severity: Impact or seriousness of failure.

Occurrence: Frequency of default.

Detectability: Level of difficulty in knowing if there is a
failure.

These failure modes are scored on a scale of 1
to 10 and then multiplied to calculate Risk Priority Number (RPN).

RPN = Severity X Occurrence X Detectability

These results reveal most problematic areas in
the design process. Higher RPN ratings should be corrected first as they have
the most impact.

Manager
implications:

1.
The idea is to focus our improvement efforts on the failures that are critical
and might have the biggest impact on the customer perceptions.

2.
This is a tool to rectify and improve existing design processes in place. It
also helps create a database of failure causes, which can be later referenced
to avoid delays.

3.
FMEA can be employed from earliest design
to improve and finally, control phase of DMAIC process.

References:

https://polarion.plm.automation.siemens.com/hubfs/Docs/Guides_and_Manuals/Siemens-PLM-Polarion-How-to-conduct-a-failure-modes-and-effects-analysis-FMEA-wp-60071-A3.pdf

https://www.isixsigma.com/tools-templates/fmea/minimizing-risks-how-apply-fmea-services/

https://www.isixsigma.com/tools-templates/fmea/fmea-preventing-failure-any-harm-done/

APPENDIX:

Figure
1: FMEA example for a car tire problem

Figure
2: Severity ratings chart

Figure
3: Occurrence ratings chart

Figure
4: Detectability ratings chart

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