The document discusses Failure Mode, Effects and Criticality Analysis (FMECA) which is a step-by-step approach to identify all possible failures in a design. It defines key terms like failure modes, effects and criticality. The document outlines the phases, purpose, benefits and techniques of FMECA including hardware and functional approaches. It provides examples of applying FMECA to analyze components and recommends corrective actions to address high risks.

1. Use Of F.M.E.C.A In Safety Analysis

2. Group Members

3. FMECA Definition
Failure Modes = Incorrect behavior of a subsystem or
component due to a physical or procedural malfunction.
Effects = Incorrect behavior of the system caused by a
failure.
Criticality = The combined impact of
 The probability that a failure will occur
 The severity of its effect
Failure Modes Effects and Criticality Analysis (FMECA) =
a step-by-step approach for identifying all possible failures
in a design, a manufacturing or assembly process, or a
product or service.

4. Evolution of FMECA
 FMEA was originally developed by NASA to improve and verify the
reliability of space program hardware.
 MIL-STD-1629 establishes requirements and procedures for
performing FMECA

5. Phases Of Process
Identify
Analyze
Act

7. Purpose of FMECA
 Select the most suitable design with high reliability and high safety
potential in the design phases.
 List potential failures and identify the severity of their effects in the
early design phases.
 Develop criteria for test planning and requirements.
 Provide necessary documentation for future design and consideration
of design changes.
 Provide a basis for maintenance management.
 Provide a basis for reliability and availability analyses.

8. Basic Questions of FMECA
 Why failures will happen (Failure mode)?
 What is the consequence when the failure occurs (Failure
effect)?
 Is the failure in the safe or danger direction (Failure
Criticality)?
 How to remove the failure or reduce its frequency?

9. Benefits of FMECA
 FMECA is one of the most important and most widely used
tools of reliability analysis.
 The FMECA facilitates identification of potential design
reliability problems
 Identify possible failure modes and their effects
 Determine severity of each failure effect
 FMECA helps
 removing causes of failures
 developing systems that can mitigate the effects of failures.
 to prioritize and focus on high-risk failures

10. Benefits of FMECA
It provides detailed insight about the systems
interrelationships and potentials of failures.
Information gained by performing FMECA can
be used as a basis for
 troubleshooting activities
 maintenance manual development
 design of effective built-in test techniques.

11. The results of the FMECA
 Rank each failure mode.
 Highlight single point failures requiring corrective action
 Identify reliability and safety critical components

12. FMECA Techniques
 The FMEA can be implemented using a hardware (bottom-up)
or functional (top-down) approach
 Due to system complexity, it isperformed as a combination of
the two methods.

13. FMECA Techniques
 Hardware Approach :
 The bottom-up approach is used when a system design has been
decided already.
 Each component in the system on the lowest level is studied one-
byone.
 Evaluates risks that the component incorrectly implements its
functional specification.

14. FMECA Techniques
 Functional Approach :
 Considers the function of each item. Each function can be
classified and described in terms of having any number of
associated output failure modes.
 The functional method is used when hardware items cannot
uniquely identified
 This method should be applied to when the design process has
developed a functional block diagram of the system, but not yet
identified specific hardware to be used.

15. FMECA Procedure
 FMECA pre-requirements
 System structure and failure analysis
 Preparation of FMECA worksheets
 Team review
 Corrective actions to remove failure modes

16. FMECA Prerequisites
 Define the system to be analyzed
 System boundaries.
 Main system missions and functions.
 Operational or/and environmental conditions.
 Collect available information that describes the system
functions to be analyzed.
 Collect necessary information about previous and similar
designs.

17. Functional Block Diagram
 Functional block diagram shows how the different parts of
the system interact with each other.
 It is recommended
 to break the system down to different levels.
 to review schematics of the system to show how different parts
interface with one another by their critical support systems to
understand the normal functional flow requirements.
 to list all functions of the equipment before examining the potential
failure modes of each of those functions.
 to include operating conditions (such as; temperature, loads, and
pressure), and environmental conditions in the components list.

18. Functional Block Diagram

19. Rate the Risks Relatively
 A systematic methodology is used to rate the risks relative to
each other. The Risk Priority Number is the critical
indicator for each failure mode.
 RPN = Severity rating X Occurrence rating X Detection
rating
 The RPN can range from 1 to 1,000
 Higher RPN = higher priority to be improved.

20. Severity Classification
 A qualitative measure of the worst potential consequences
resulting from a function failure.
 It is rated relatively scaled from 1-10.

21. Severity Classification
1 Failure would cause no effect.
2 Boarderline pass but still shippable.
3 Redundant systems failed but tool still works.
4 Would fail manufacturing testing but tool still functions with degraded performance.
5 Tool / item inoperable with loss of primary function. No damage to other components on
board. Failure can be easily fixed (for example, socketed DIP chips).
6 Tool / item inoperable with loss of primary function. No damage to other components on
board. Failure cannot be easily fixed (true if not field repairable).
7 Tool / item inoperable, with loss of primary function. Probably cause damage to other
components on board or system.
8 Tool / item inoperable with loss of primary function. Probably scraping one or more
PCBAs.
9 Very high severity ranking. A potential failure mode affecting safe tool operation and/or
involves noncompliance with government regulation with warning.
10 Very high severity ranking when a potential failure mode affects safe tool operation
and/or involves noncompliance with government regulation without warning.

22. Probability of Occurrence
 Probability that an identified potential failure mode will
occur over the item operating time.
 It is rated relatively scaled from 1-10.

23. Occurrence Classification
10 >= 50% (1 in two)
9 >= 25% (1 in four)
8 >= 10% (1 in ten)
7 >= 5% (1 in 20)
6 >= 2% (1 in 50)
5 >= 1% (1 in 100)
4 >= 0.1% (1 in 1,000)
3 >= 0.01% (1 in 10,000)
2 >= 0.001% (1 in 100,000)
1 Almost Never

24. Detection rating
 A numerical ranking based on an assessment of the
probability that the failure mode will be detected given the
controls that are in place.
 It is rated relatively scaled from 1-10.

25. Detection Rating
1 Detected by self test.
2 Easily detected by standard visual inspection.
3 Symptom can be detected. The technician would know exactly what the source of the
failure is.
4 Symptom can be detected at test bench. There are more than 2-4 possible candidates for
the technician to find out the sources of failure mode.
5 Symptom can be detected at test bench. There are more than 5-10 possible candidates for
the technician to find out the sources of failure mode.
6 Symptom can be detected at test bench. There are more than 10 possible candidates for
the technician to find out the sources of failure mode.
7 The symptom can be detected, and it required considerable engineering
knowledge/resource to determine the source / cause.
8 The symptom can be detected by the design control, but no way to determine the source /
cause of failure mode.
9 Very Remote. Very remote chance the Design Control will detect a potential
cause/mechanism and subsequent failure mode. Theoretically the defect can be detected,
but high chance would be ignored by the operators.
10 Absolute uncertainty. Design Control will not and /or cannot detect a potential
cause/mechanism and subsequent failure mode; or there is no Design Control.

26. FMECA CASE STUDY
 Component = D1
 Function = restricting the direction of current
 Failure = short
 Cause = Physical Damage
 Effect = Reverse current

27. FMECA CASE STUDY
 Severity = 7
 Occurrence = 5
 Detection = 9
 RPN = 7*5*9 = 315

28. FMECA Worksheet
Component
Function
Severity
Occurrence
detection
RPN
Failure
Cause
Effect
Recommendation
D1
restricts the
direction of
current
7 5 9 315 short
Physical
Damage
Reverse
current
Change test
procedure

29. Corrective Actions
 RPN reduction: the risk reduction related to a corrective
action.

30. FMECA Checklist
 System description/specification
 Ground rules
 Functional Block Diagram
 Identify failure modes
 Failure effect analysis
 Worksheet (RPN ranking)
 Recommendations (Corrective action)
 Reporting

31. Simple Example: Flashlight
This flashlight is for use by special operations forces involved in
close combat missions (especially hostage rescue) during low
visibility conditions in urban areas. The light is to mounted coaxially
with the individual's personal weapon to momentarily illuminate
and positively identify targets before they are engaged. The exterior
casing including the transparent light aperture are from an existing
ruggidized design and can be considered immune to failure.

32. Simple Example: Flashlight (cont.)
How can it fail?
What is the effect? Note
that Next Higher Effect =
End Effect in this case.
Part

33. Severity
 SEVERITY classifies the degree of injury, property damage,
system damage, and mission loss that could occur as the
worst possible consequence of a failure. For a FMECA these
are typically graded from I to IV in decreasing severity.
 The standard severities defined in MIL-STD1682 may be
used or equipment specific severities may be defined with
customer concurrence (recommended).

34. Simple Example: Flashlight (cont.)
 Severity
 Severity I Light stuck in the “on” condition
 Severity II Light will not turn on
 Severity III Degraded operation
 Severity IVNo effect

35. Simple Example: Flashlight (cont.)
Item Failure Mode End Effect Severity
bulb dim light flashlight output dim III
no light no flashlight output II
switch stuck closed constant flashlight output I
stuck open no flashlight output II
intermittent flashlight sometimes will not turn on III
contact poor contact flashlight output dim III
no contact no flashlight output II
intermittent flashlight sometimes will not turn on III
battery low power flashlight output dim III
no power no flashlight output II

36. Criticality
 CRITICALITY is a measure of the frequency of occurrence
of an effect.
 May be based on qualitative judgement or
 May be based on failure rate data

37. Simple Example: Flashlight (cont.)

38. Simple Example: Flashlight (cont.)
Can circled items be designed out or mitigated?
(There may be others that need to addressed also.)

39. Integrated FMECA
 FMECAs are often used by other functions such as
Maintainability, Safety, Testability, and Logistics.
 Coordinate your effort with other functions up front
 Integrate as many other tasks into the FMECA as possible and as
make sense (Testability, Safety, Maintainability, etc.)
 Integrating in this way can save considerable cost over doing the
efforts separately and will usually produce a better product.
 If possible, use the same analyst to accomplish these tasks for the
same piece of hardware. This can be a huge cost saver.

40. FMECA Facts and Tips
 FMECAs should begin as early as possible
 This allows the analyst to affect the design before it is set in stone.
 If you start early (as you should) expect to have to redo portions as
the design is modified.
 FMECAs take a lot of time to complete.
 FMECAs require considerable knowledge of system
operation necessitating extensive discussions with
software/hardware Design Engineering and System
Engineering.
 Spend time developing ground rules with your customer up
front.