Forum: Reliability & Maintainability Questions and Answers
Posted by: Juan C. Rodenas
Date posted: Mon Oct 9 7:53:56 US/Eastern 2000
Subject: Non-mechanical Reliability
We are a spanish company, just introducing on the reliability studies, due to our compromise at military sales. Right now, I am trying to obtain as much data as I can about this issues. I have found plenty of data for electronic reliability. The only reference I have about non-electronic reliability data is NPRD-95, but I have no idea of what class of mechanical data I will find in this data, prior to the adquisition.For example, I will need data about pump, hidraulyc valves, etc. Can somebody explain to me what kind of data I can expect to find in this book. or where can I obtain that information.
Posted by: Chad
Date posted: Thu Oct 5 13:38:35 US/Eastern 2000
Subject: Reliability and Confidence Allocation
In many cases we need to allocate system reliability requirements down to component level. Reliability allocation is quite straight forward by using block diagram; however, what would be a good approach to allocate confidence requirement? If I demostrated reliability at 90% confidence for all components, can I calculate system reliability by using block diagram and claim 90% confidence at system level without system level testing? Any good suggestions, reference?
Posted by: JJC
Date posted: Wed Oct 4 7:55:26 US/Eastern 2000
Subject: Confidence Levels
Could somebody provide me with a definition or a source of reference for confidence levels? i.e. 60% confidence level, Upper CL and Lower CL.
Also, how is the CL determined? Thanks in advance
Posted by: Richard Golek
Date posted: Thu Sep 21 12:42:14 US/Eastern 2000
Subject: glass thermistors with axail leads
We have begun forming the leads on axial thermistors with glass bodies. 50 to 90X visual inspection reveals small cracks near the glass/lead interface on a small percentage of the parts. Our own test program has just begun, and the vendor has not been able to supply more data. I am looking for comments on what the long term humidity and resistance effects may be, paticularly in a tropical but benign environment. Thank you.
Posted by: Sheila Prather (email@example.com )
Organization:Northrop Grumman Corporation
Date posted: Wed Sep 20 14:25:14 US/Eastern 2000
Subject: Operational Parameter Translation - Question #2
This is a followup to my question posted on 9/11/00 regarding the TR-89-299. I've noted the caution that should be exercised when using this document...this question addresses the examples that are published in the "Reliability Toolkit: Commercial Practices Edition". I see where example #1 has been corrected from the previous 4/93 version of the toolkit; but, my question rests with example #2.
Looking at Section 220.127.116.11 of TR-89-299, in example #2 why was the field number for flight hour determination based on 1,672 hours versus 1,000 hours (50% of 2,000)?