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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum (src_forum@alionscience.com )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Original Message:

Posted by: Andrew Rowland (darowland@aep.com )
Date posted: Wed Dec 4 12:26:23 US/Eastern 2002
Subject: Life Data Analysis
Message:
I am trying to perform life data analysis which I plan to roll-up to an RBD. I am doing this to provide examples in an attempt to convince management that these analyses are important for an organization concerned with reliability. Obviously, it will be more poignant if I use actual plant systems, but I want to ensure that my results are the best they can be. In light of this, I have a couple of questions. I thank you in advance for your input. The system I have chosen to model is comprised of four identical “channels” of electronics. System level functions are satisfied by a 2-out-of-4 arrangement of the channels. The system has been in service for 25 years (late 70’s). Use of a computerized failure reporting system began in May 1991. Thus, the date of failures and time taken to repair each failure after May 1991 are easy to obtain. However, there is no failure data for the system prior to May 1991. The only thing I know for certain is that each channel operated failure free from May 1991 until the first failure was reported. Intuitively, the first failure found in the computerized system for each channel would be a right censored data point. The time of suspension would be the date of failure minus May 1991. Is this the correct way to treat this situation when performing life data analysis? Would the model developed only be applicable to a channel during the 15-25 year portion of it’s life? That is, I couldn’t expect my model to describe the behavior of a channel that was “brand new”.


Reply:

Subject: Life Data Analysis
Reply Posted by: Coit (coit@rci.rutgers.edu )
Date Posted: Wed Dec 4 14:24:57 US/Eastern 2002
Message:
See "Modeling lifetimes with unknown initial age" by M. S. Finkelstein, Reliability Engineering & System Safety," vol 76 (2002), pp. 75-80. It might help - it might not.


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