systems engineering – risk analysis with fmea
DESCRIPTION
Systems Engineering – Risk Analysis with FMEA. Special Topics Fishbone Chart FMEA. Risk/Failure Models. At the ‘project’ level. At the system or device level. Common methods include Fishbone analysis or FMEA FMEA – Failure Modes and Effects Analysis. Fishbone Chart. - PowerPoint PPT PresentationTRANSCRIPT
Systems Engineering – Risk Analysis with FMEA
Special TopicsFishbone ChartFMEA
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Risk/Failure Models
At the ‘project’ level.
At the system or device level. Common methods include Fishbone
analysis or FMEA FMEA – Failure Modes and Effects Analysis
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Fishbone Chart
‘Cause and Effect’ Analysis Create an Ishikawa or Fishbone Chart Head is ‘Problem’ – Skeleton are the ‘Causes’ Typical categories, 5M’s + E
Man Machine Material Method Measurement Environment
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Industrial Monitoring Sensor
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Create a Fishbone Chart for ‘Sensor Not
Working’
Analysis Tool – FMEA
Failure Mode and Effects Analysis
FMEA is an ‘enhanced’ Cause and Effect Analysis. (the 5M’s plus E) Do Fishbone Chart for Industrial Sensor.
Apply FMEA to a Design or Processes at many levels.
Systems often have many SPFs – single points of failure.
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Design Tool – FMEAThe Concept of FMEA:
People Make Mistakes Products and Processes Fail
Anticipate these errors and eliminate them with design or process changes !!
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FMEA Example
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How many ways can a
floppy disk be inserted ??
What design features make this possible??
FMEA Steps-The traditional approach
1. Team activity2. Select component, system, process step, etc.3. Identify possible failure modes.4. Identify causes of failure modes.5. Identify effects of failures.6. Estimate (1-10 ranking):
1. Occurrence – how often (1=not, 10=often)2. Severity – how bad (1=not, 10=severe)3. Detection – how easy (1=easy, 10=difficult)
7. Calculate RPN – ‘risk priority number’
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FMEA RPN example
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Occ Sev Det RPN Comments 1 1 1 1 No Problem 1 10 1 10 No action, easy to detect. 1 1 10 10 No action, not often or severe. 1 10 10 100 Action 10 1 1 10 Chronic problem, fix ? 10 10 1 100 Chronic and severe, fix 10 1 10 100 Chronic and customer issues, fix 10 10 10 1000 Bad, Bad, Bad – top priority
Rules for OSD ValuesThreshold for Action – VariesThresholds 55-100 (?)
10From National Instruments
11From National Instruments
12Detection in Design or Manufacturing
POTENTIAL FAILURE MODE AND EFFECTS ANALYSIS
Page FMEA Number
Part Number Design or Process Responsibility Prepared by Telephone #
Original FMEA Date FMEA Revision Date
Core Team
Design Item or Process Function Requirements
Potential Failure Mode Potential Effect(s) of FailureSev
Class
Potential Cause(s) / Mechanism(s) of Failure
Occ
Current Design or ProcessControls
Det
RPN
Recommended ActionsResponsibility & Target
Completion DateActions Taken
Sev
Occ
Det
RPN
System Subsystem Component
Design FMEA Process FMEA Internal Use Only
.
13Many versions of this chart…
Occurrence and Severity
O and S are often the two critical factors and some analysis just looks at these two.
14From Dieter
Industrial Monitoring Sensor
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FMEA Summary
Combines ideas of ‘Cause and Effect’ chart, mistake proofing, and risk.
Useful to identify and prioritize possible failure modes and fixes.
Possible Fixes : High reliability components, De-rate components, Redundancy, Change the design.
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FMEA- A Requirements Approach
FMEA often starts with: Identify possible failure modes. How? – guess, experience, brainstorm, etc.
Consider – Requirements are what the system is supposed to do. Counter-requirements (not being met) are failure modes. Use counter-requirements to populate the FMEA table.
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Design FMEA Example
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Design FMEA
Coyote Hoist
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Class Discussion – Process FMEA You are responsible for developing a process to stuff
several hundred envelopes for a charity group.
Each envelope is to contain three separate flyers and a cover sheet with the recipients name on it. After folding, the name must show in the cutout in the envelope. The final step is to seal and place stamps on the envelope for mailing.
Develop a PFMEA* for this process.
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*Process FMEA