Forum: Reliability & Maintainability Questions and Answers

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Posted by: Clay Davis
Date posted: Tue Aug 15 2:50:17 US/Eastern 2000
Subject: MTBF Calculations (Customer Complaint)
Message:
Several of our computers have an MTBF of 50,000 hrs. However, a major customer states that if they purchase 100 systems 9 will fail in the first 6 months and another 9 will fail by the end of the first year.
Agreed this is numerically accurate (1/(50,000*365*24*100)) - however this does not seem right. I tried to explain that not every failure will cause a system failure (ie a capacitor) but they did not agree without us being able to prove these parts are truly redundant (which they are probably not). Thoughts? There has to be something that I am missing. Thank you for your help. --Clay

Replies:
Computer MTBF Calcualtions
Bruce Dudley Tue Aug 22 11:29:17 US/Eastern 2000

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Posted by: Dominique Roy (doroy@transport.bombardier.com )
Organization:Bombardier
Date posted: Mon Aug 14 13:24:34 US/Eastern 2000
Subject: Environment factor conversion for NPRD-95
Message:
Some of our suppliers have to provide reliability calculations for mechanical parts. Our spec. is calling the use of NPRD-95, Gm environment for mechanical parts reliability predictions. Some of the parts failure rates found are available only in a Gf ou Gb environment. Are there conversion factors that can be applied to the base failure rate to reflect the Gm environment for mechanical parts?
Needed: From Gb, Gf, N, Ai, Au, ARW, CL to Gm. Thanks!

Replies:
Environmental Conversion Factors
Bruce Dudley Tue Aug 22 10:43:00 US/Eastern 2000

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Posted by: KEITH WALKER (KEITH.WALKER@THAAD.ARMY.MIL )
Organization:US ARMY
Date posted: Thu Aug 10 22:58:15 US/Eastern 2000
Subject: QUALITY fACTORS AND BELLCORE RELIABILITY PREDICTIONS
Message:
DOES ANYONE KNOW OF ANY SELECTION GUIDELINES FOR THE QUALITY FACTOR IN BELLCORE? I AM SPECIFICALLY INTERESTED IN THE PREDICTION OF MILITARY EQUIPMENT RELIABILITY WHEN COMMERCIAL PARTS ARE USED.
ANY TECHNICAL JOURNAL REFERENCES WOULD BE MOST APPRECIATED. THANKS KEITH WALKER

Replies: (list all replies)
Commercial Quality Factors
Bruce Dudley Mon Aug 14 14:43:26 US/Eastern 2000
Bellcore Quality Factors
Floyd Kreuze Tue Aug 15 9:53:16 US/Eastern 2000

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Posted by: Bob Valerius (robert_m_valerius@md.northgrum.com )
Organization:Northrop-Grumman Oceanic & Naval Systems
Date posted: Wed Aug 9 8:45:07 US/Eastern 2000
Subject: ESS
Message:
Hi
I am wondering what the current thinking on ESS is. It appears to me that activity in this arena is waning as most screening is no longer viewed as needed, especially with so many COTS products. Is this an accurate view? Comments and emails from those with experience would be appreciated.

Replies:
ESS testing of COTS
Bruce Dudley Thu Aug 10 14:02:41 US/Eastern 2000

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Posted by: Thomas D'Eufemia (deufemia@teas.eglin.af.ml )
Organization:Sverdrup TEAS
Date posted: Mon Aug 7 15:15:22 US/Eastern 2000
Subject: R and M data collection
Message:

Does anyone have a nice neat format for R$M data collection

Replies:
R/M Test data collection system
Bruce Dudley Thu Aug 10 15:15:41 US/Eastern 2000

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