Forum: Reliability & Maintainability Questions and Answers
Posted by: Fred Levesque
Date posted: Fri Dec 1 9:31:16 US/Eastern 2000
Subject: Environmental Conversion Factors
I am looking at the RAC Reliability Toolkit: Commercial Practices Edition, page 176. I want to convert a system series MTBF from a particular temperature and environment to a different temperature and a different environment. Do I apply both the environmental conversion factor from the environmental table AND the temperature conversion factor from the temperature table? I was previously told to use ONLY the environmental factor, which does not seem reasonable.
Posted by: John Sine (firstname.lastname@example.org )
Date posted: Thu Nov 30 15:39:38 US/Eastern 2000
Subject: Component Derating Guidelines
Can anyone identify one or two good sources that discuss derating guidelines for electronic components?? Thanks for your help.
Posted by: SPM (email@example.com )
Date posted: Thu Nov 30 9:48:11 US/Eastern 2000
Subject: Reliability Prediction Calculations
Being new to the field of reliability, I would be grateful for some advice.
I have used MIL-HDBK-217 to calculate predictions i.e. 500 fpmh. However I have been asked to provide a prediction for a stipulated operational life i.e. a failure rate is to be less than 500 fpmh over an operational life of 20 years. At the same time I have been asked to predict the failure rate after 1 year and 10 years. I have managed to calculate the generic failure rate but donít know how to proceed in proving that it is within the operational life or what the failure rate will be after 1 yr and 10 yrs. I believe this is typical of Bellcore standards (1209, 1221 and 332) to provide this sort of information. Can anybody provide me with some guidelines as to how I would go about this calculation? I hope I have made the question clear and I look forward to any help that can be provided.
Posted by: Henry Davis (firstname.lastname@example.org )
Date posted: Wed Nov 29 12:21:55 US/Eastern 2000
Subject: HALT/HAST testing
We are attempting to develop and correlate a service life
specification requirement with a HALT/HAST test on an Line Replaceable Unit. We will need to develop the HALT/HAST test. Alternatively, we have a TAAF definition including duration, temp cycling and vibration levels and want to translate this to a service life number. Would appreciate any data or information on methodology (examples would be useful)for doing either of the above. Thanks for any assistance.
Posted by: Michael (email@example.com )
Date posted: Tue Nov 28 20:22:10 US/Eastern 2000
Subject: Quality Factor of MIL-HDBK-217F
I wonder what quality factors in Mil-217 mean. For each parts, quality factor is different with each other. Please, let me know which books or standards I could refer. In advance, thank you!!