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Greg Baker © 2004

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Failure Modes Effects and Criticality Analysis

(FMEA/FMECA)Part-2

MQM_RY_S6

Dr. O. Alsahli

Reliability and Quality Principles MQM_RY_S6

Greg Baker © 2004

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FMEA & FMECA Standards

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O. Alsahli

• (BS 5760-part5) Guide to Failure Modes, Effects and Criticality Analysis .

• (MIL-STD-1629A) Procedures for performing a Failure Modes, Effects and Criticality Analysis .

• IEC 60812 “Procedures for failure mode and effect analysis (FMEA)”

• (NHB 5300) Failure Modes and Effects Analysis (FMEA), and Critical Item List (CIL), requirements for NASA programs .

• SAE J-1739 “Potential Failure Mode and Effects Analysis in Design (Design FMEA) and Potential Failure Mode and Effects Analysis in Manufacturing and Assembly Processes (Process FMEA) and Effects Analysis for Machinery (Machinery FMEA)”

Greg Baker © 2004

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FMEA Info Centre

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www.fmeainfocenter.com

Search News Alerts Community Examples Guides and Introductions

Handbooks

Books Papers -

AbstractsPresentations Services Standards Tools

Greg Baker © 2004

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Failure analysis and preparation of FMECA worksheets

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O. Alsahli

Greg Baker © 2004

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Function

Sub-Function

Sub-Function

Sub-Function

Sub-Sub-Function

Sub-Sub-Function

Sub-Sub-Function

1. A unique reference to an element (subsystem or component) is given. It may be a reference to an id.

2. The functions of the element are listed. It is important to list all functions.

3. The various operational modes for the element are listed.

Greg Baker © 2004

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Description of failure

(4) Failure Mode (O.C., S.C., No Power,..)

(5) Failure Cause (Temp., Load, Aging ..)

(6) Failure Detection (Testing, Alarm,

Detection Probability: 1-2 Very high, 3-4

High, 5-7 Moderate, 8-9 Low, 10 Very low

Greg Baker © 2004

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Failure Effect

(7) On the Subsystem (Local effect)

(8) On the System function (Global effect )

Are the consequences of each failure mode on item operation, function or status.

Can be described in terms of what the users experience or what would be drawn to their attention.

Greg Baker © 2004

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Failure Rate (Occurrence)

1-2 Very unlikely Once per 1000 years .

3-4 Remote Once per 100 years

5-6 Occasional Once per 10 years

7-8 Probable Once per year

9-10 Frequent Once per month or more often

Greg Baker © 2004

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p bXQXEXA

p edicted failure rate

bBase failure rate

XQ Quality factor

XE Environment factorXA Application stress factor

......

Pr

Greg Baker © 2004

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Severity ranking

10 Catastrophic Failure

7-9 Critical Failure

4-6 Major Failure

1-3 Minor Failure

Greg Baker © 2004

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MQM_RY_S6

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Severity System/Mission People/Enterprise

1 No or Negligible effect

No injury/ No or negligible production loss.

2-3 Less than 10% loss of capability

Minor injury/ Minor production loss.

4-6 10% to 40% loss of capability

Moderate injury with full recovery/ Significant production loss.

7-9 40% to 80% loss of capability

Severe injury and long term damage/ Moderate plant and production loss.

10 100% loss of capability

Loss of life / Major plant and production loss .

Greg Baker © 2004

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Criticality Analysis

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Criticality Assessment (Risk Ranking)

Risk ranking (Criticality Analysis)

The risk related to the various failure modes is often presented either by a:

Criticality Matrix (Military Standard technique), or

Risk Priority Number (RPN):

The objective of the criticality assessment is to determine priorities the failure modes discovered during the system analysis on the basis of their effects and occurrence likelihood.

Greg Baker © 2004

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Criticality Matrix

Criticality is a combinations of the Severity of an effect and the probability or expected frequency of its Occurrence

5 A C C D D

4 A B C C D

3 A B B C C

2 A A B B C

1 A A A A A

1 2 3 4 5

Severity

Occ

urr

en

ce

Greg Baker © 2004

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Risk Priority Number (RPN)

Greg Baker © 2004

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Risk Priority Number (RPN)

This method calculates the risk priority number for a part failure mode using three factors: (1)Failure effect severity, (2)Failure mode occurrence probability, and (3)Failure detection probability.More specifically, the risk priority number is computed by multiplying the rankings (i.e., 1–10) assigned to each of these three factors.

RPN = O * S * D where

RPN is the risk priority number.O is the occurrence ranking.S is the severity ranking. D is the detection ranking.

Greg Baker © 2004

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Critical Items List

The Critical Items List is prepared to facilitate communication of important analysis results to management.

Greg Baker © 2004

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Team review

• Design engineer (hardware/software/systems)

• Test engineer• Reliability engineer• Quality engineer• Maintenance engineer• Field service engineer• Manufacturing/process engineer• Safety engineer

Greg Baker © 2004

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Risk reducing measures Possible actions to correct the

failure and restore the function or prevent serious consequences are listed. Actions that are likely to reduce the frequency of the failure modes should also be recorded.

Greg Baker © 2004

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Advantages of FMEA

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There are many benefits of performing FMEA, Including a systematic approach to classify hardware failures, reduces development time and cost, reduces engineering changes, easy to understand, serves as a useful tool for more efficient test planning, highlights safety concerns to be focused on, an effective tool to analyze small, large, and complex systems, useful in the development of cost-effective preventive maintenance systems, provides safeguard against repeating the same mistakes in the future, improves customer satisfaction, useful to compare designs, a visibility tool for manager, and useful to improve communication among design interface personnel.

Greg Baker © 2004

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FMEA example

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FMEA Pressure Cooker

1. Safety valve relieves pressure before it reaches dangerous levels.2. Thermostat opens circuit through heating coil when the temperature

rises above 250° C.3. Pressure gage is divided into green and red sections. "Danger" is

indicated when the pointer is in the red section.

Greg Baker © 2004

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FMEA example

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O. Alsahli

FMECA - RPN

الصندوقي المخططللوثوقية

الهيكل محرك وال

نظام التحكم

نظام االتصاالت

المفيد الحمل

A=0.60A=0.60 B=0.85B=0.85 C=0.91C=0.91

D=0.79D=0.79 E=0.83E=0.83

F=0.94F=0.94 G=0.97G=0.97 H=0.70H=0.70

K=0.52K=0.52

D=5 , S=7 D=6 , S=8

D=1 , S=5 D=2 , S=9

D=3 , S=4 D=6 , S=2

D=9 , S=3

D=7 , S=7

D=4 , S=8

Greg Baker © 2004

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FMEA example

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FMECA – RPN

حراج درجة المكونات حدد ل ة O لألكثر RPNطريقةوفقا O وفقا ورتبهاالضرر ، حراجة شدة ومعامل العطل كشف وعامل وثوقية بأن O علما

معامل تحديد للطالب يترك ، المخطط في مبينة الجزئية للمكوناتاألعطال حدوث الوثوقية Occurrence( O)معدل معطيات على بناء

المكونات . لتلك

Greg Baker © 2004

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FMEA example

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FMECA – RPN

ITEM S O D RPN

A 5 7 5 175

B 6 8 2 96

C 9 3 1 27

D 1 5 3 15

E 2 9 2 36

F 3 4 1 12

G 6 2 1 12

H 4 8 4 128

K 7 7 5 245

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