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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)