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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: IC
Date posted: Mon Mar 5 16:07:21 US/Eastern 2007
Subject: Reliability Apportionment
Message:
I am looking for information in relation to apportionment and the techniques used for calculating it. I have calculated the apportionment for a System with 6 sub-systems (Using the Equal Apportionment Technique from MIL-HDBK-338). NOW I am trying to calculate the apportionment for the sub systems with the new information that each sub system has now been "weighted" (i.e sub sys 1 will be responsible for 20% fo all system failures and Sub sys 2 47% etc etc). Can anybody tell me how I will calculate the new reliability apportionment based on the "weighted" factors or let me know of any techniques/equations that I can use.

Thanks for the help.


Reply:

Subject: Reliability Apportionment
Reply Posted by: John Cloarec
Date Posted: Tue Mar 6 6:26:38 US/Eastern 2007
Message:
The Equal Apportionment Technique is not very sophisticated, that's why you need another method for subsystem apportionment. In the same document MIL-HDBK-338 you can find a more sophisticated and useful method : Feasibility of Objectives Technique which use 4 parameters and a set of simple formulas. You have no limitation in the decomposition of your system. You can put your model in a excel file and redo the calculation any times you want to assess the impact of some changes in the value of each parameters. This method is interesting because there is a great analogy with reliability prediction as per MIL-HDBK-217. The only limitation is that the system configuration is assumed to be serial (no redundancy). I've conducted a survey for EdF in France. The papers I have are all in French ... What we found is that the best compromise for : - reliability allocation is the Feasibility of Objectives Technique method, - maintainability allocation is the method described by Arsenault & Roberts in R&M of Electronic System, Ed. Pitman. If you can read French, I can send you a scan of my papers. Regards. John


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