Download - Chapter 13 Reliability
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Quality Control andImprovement, Reliability,Liability
P. King/Chapter 13 overview
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Reliability is:
A characteristic that describes howgood a device is.
Must be planned for, designed in bothin terms of the initial product and inmaintenance of that product.
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Failure is:
The degradation of the performance of adevice (process) outside of a specified value
AND non-performance or inability to perform
its function for a given time period withinspecified conditions.
Defect: imperfection
Deficiency: lack of conformance to specs
Fault: Cause of failure
Malfunction: unsatisfactory performance
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Failure Measures
Real life failure: fact of life, definenormal operation, anticipate worst, try
to design out.Failure rate typically = #failures/unittime = failures/million hours for
devices.
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Unreliability is:
A measure of the potential for failure of adevice (or process.)
Leads to high cost, wasted time,inconvenience, poor reputation, unsafeoperation, …
- 9/9/99 more than 10,000 stepladders
recalled by Home Depot – steps too short,improperly attached (RIDGID ladders,Louisville Ladder Co, Louisville KY)
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Quality is:
The ability to provide stated needsNOW (and is implied during warranty
period.)Warranty period: that period of timethat you guarantee to refund/replace/fix
your product.
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Safety & Quality in HealthCare:
HHS Secretary Tommy G. Thompson today(10/11/2001) announced the release of $50
million to fund 94 new research grants,contracts and other projects to reducemedical errors and improve patient safety.
This research initiative is part of HHS' broader
efforts to improve the quality of care in America and better assure safety acrosshealth care settings.
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Reliability Implies:
MTBF of x years (for example, e-1 fail in5 years), proportional to the probability
of service over a period of time, T.= performs stated function, without
failure (even with misuse) in the stated
environment, for a specified period oftime.
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Vanderbilt: Reliability & RiskEngineering & Management
NSF IGERT awarded 2001
$2.7 M over 5 years
BME/ChE/CE/EECS/MT/Math/ME/Owen
2 year support toward PhD
Sankaran Mahadevan, CE
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Infant Mortality
<-Useful Life ->
Wearout
Joints,Welds,
Contamination,Misuse
Corrosion,Cracking,
Wear,Crazing,Shorts
Screening,Design,Burn-in
-- Design,PreventiveMaintenance,Replacement,Repair
Time ->
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F a i l u r e R
a t e
Time->
Friction,Fatigue,Erosion,Corrosion,
Cracking,Lack of PM
PM,
Replacement
Misassembly
<- Useful Life ->
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F a i l u r e R
a t e
Time ->
Debug errors,Spec. Errors,
Special Cases
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F a i l u r e
R a t e
Time ->
QI
QIPM
Lawsuit Lawsuit
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Product Liability
Negligence - legal
Strict Liability - legal
Breach of warranty – legal
Defects
Failure to warn
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Negligence
You owe a duty of care to another
The standards for that care have been
breached As a result a compensable injury results
There are damages or injury to the
plaintiff
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Strict Liability
The PRODUCT is defective ordangerous.
Risk is too high (risk/benefit higher thancompetition, etc.)
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Breach of Warranty
Implied Merchantability (“King’sPacemakers”)
Implied Warranty for particular purpose(pacemaker)
Breach of express warranty (written or
oral contract: cures 100%)
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Defect
Actual defect (sharp edges, …)
Consumer expectations
Risk/benefit
State of the art
Defective warnings
Inadequate guarding…
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Failure to warn!
You have a duty to warn. If you do notwarn that coffee is hot, you are likely to
get in trouble…
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Examples
Coffee burn
“found with head trapped in side rails…”
Stepladder recall
Fluidized air therapy bed
X-ray/Cobalt therapy accident
Morphine infusion 3 hours not 24
LMA – cyanosis (see MAUDE)
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Some final key phrases
Misuse
Negligent selection
Failure to inspect
Use with knowledge of defect
Alterations
Disclosure through MAUDE (FDA)
Disclosure through CPSC (non-FDA)