Reliability Data Collection
and Analysis
Benbow and Broome (Ch 15, 16 and 17)
Presented by Dr. Joan Burtner
Certified Quality Engineer
Associate Professor of
Industrial Engineering and Industrial Management
Overview
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Chapter 15 (Collection)
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Types of data
Data sources
Collection methods
Management of data
Chapter 16 (Use)
 Summarization of data
 Preventive and corrective action
 Measures of effectiveness
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Chapter 17 (Failure analysis tools)
 FMEA, FMECA
 FTA
 FRACAS
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 2
Censored Failure Data
 Right censored data
• Exact failure times collected through the end of the test period
• Some items may still be functioning at end of test period
 Left censored data
• Knowledge that failure happened before a certain time
• Occurs when items are not checked prior to testing
• Failure is observed at the first examination
 Interval censored data
• Knowledge that failure happened between 2 times
• Occurs when items are checked at intervals (eg. every 2 hrs)
• Failure is observed at the first examination
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 3
Reliability Data Sources
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Laboratory tests before delivery to customer
 “Clean”
 Unrealistic
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Field service data (after delivery to customer)
 Difficult to determine relevant factors
 Realistic
 Provides input for future design changes
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Note: Most reliability data collection looks at failure/nonfailure. However, effective managers may collect data on
degradation of customer satisfaction with non-failed
products or processes
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 4
Reliability Data
Management
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Design of the product failure database
should involve a variety of stakeholders.
What data will be collected?
Where will the data be kept?
Who will have access to the data?
How long will the data be kept?
What are the backup and security
procedures?
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 5
Data Summarization
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Calculations
 Hazard function – failure rate as a function of
time
λ (t) = Fraction of failures during time period
Amount of time during the period
 Reliability function – reliability as a function of
time
R(t) = Number surviving at the end of the time period
Number of units tested
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 6
Data Presentation
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Control Charts
Histograms
Probability density function graphs
Cause and effect diagrams
Scatter diagrams
Pareto charts
Comparisons of before/after preventative or
corrective action initiatives
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 7
Ch. 17 Tools - FMEA
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Failure Mode and Effects Analysis (FMEA)
Purpose: “anticipation and migration of the negative
effects of possible failures before they occur.”
Ideally implemented by a cross-functional team that
may even include customers
Applicable to all stages from product and process
design and through delivery
Includes the development of risk priority values
which are subject to interpretation
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 8
FMEA Process Steps
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Develop team, collect data, identify all possible
failure modes.
Calculate risk priority number (rpn) for each mode
based on estimations of severity (S), occurrence (O),
and detection (D).
 Estimations typically range from 1 to 10.
 There are many acceptable guidelines for assigning the
values.
 The rpn for each mode equals S x O x D.
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Prioritize failure modes and interpret the results.
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 9
FMEA Interpretation
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Traditional method: Sort failure modes by rpn number and
address modes with highest rpn numbers first.
 Because we are dealing with estimations, look for natural groupings rather
than absolute ranks.
 May use product of severity and detection to break ties.
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Alternative method: Do not calculate rpn. Instead, sort by
severity rank, then occurrence rank, and finally detection rank.
 This allows you to address all of the highest severity failure modes before
the medium and lower severity modes.
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Regardless of the method used, preventive and corrective
action plans should be developed for high priority failure
modes.
Thorough documentation is essential.
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 10
Ch. 17 Tools - FMECA
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Failure Mode and Effects and Criticality Analysis
(FMECA)
Purpose same as FMEA
FMECA uses Severity (S) and Occurrence (O) ratings
on a scale of 1 to 10, where 10 is highest.
Values are not multiplied. Instead they are placed on
a graph with S on x-axis and O on y-axis
Failure modes in the top right quadrant are
addressed first.
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 11
Ch. 17 Tools – FTA and STA
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Fault Tree Analysis (FTA)
Success Tree Analysis (STA)
Graphical representation of identified failure mode
Purpose to help identify root cause of product
failure or steps to help ensure product success
See Figure 17.1 (input/output symbols) p.227
See Figure 17.2 and 6.2 for complete FTA diagrams
See Figure 17.4 STA diagram
Voting OR gate p.228
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 12
Ch. 17 Tools - FRACAS
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Failure Reporting, Analysis, and Corrective Action System
(FRACAS)
Provides an organized, disciplined approach for dealing with
failures that actually occur.
Guidelines for implementing FRACAS
 Assign responsibility for FRACAS implementation to individual or
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department
Require that all failures be reported promptly
Apply FRACAS throughout the product life cycle
Develop timelines for analysis and corrective / preventive actions
and reports
Alert next higher level of management WRT non-compliance
issues
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 13
References
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Course Text:
 Benbow, D.W. and Broome, H.W., Ed. (2009). The
Certified Reliability Engineer Handbook . Milwaukee,WI:
ASQ Quality Press.
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Additional Sources
 Christensen, E.H., Coombes-Betz, K.M., and Stein, M.S.
(2006). The Certified Quality Process Analyst Handbook.
Milwaukee: ASQ Quality Press.
 Westcott, R.T., Ed. (2006). Certified Manager of
Quality/Organizational Excellence Handbook (3rd ed.).
Milwaukee: ASQ Quality Press.
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 14
Contact Information
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Email:
[email protected]
US Mail:
Mercer University School of Engineering
1400 Coleman Avenue
Macon, GA
Phone: (478) 301- 4127
ETM 591 ISE 427 Reliability Data
Dr. Joan Burtner, Associate Professor of Industrial Engineering
Slide 15