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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: Ken
Organization:ST
Date posted: Sat Aug 31 0:54:45 US/Eastern 2002
Subject: maintainability prediction
Message:
DO we provide any safety factor for maintainability prediction? For e.g if i predicted 4 hours for a specific maintenace level in army context, do i allow contractor to specify the guaranteed MTTR or Mmax to be at 4.5 hours instead of the predicted value? In reliabilty prediction we are taught that predicted reliabilty must be at least 2 times higher than guaranteed reliabilty. Does that apply for Maintaninability Prediction as well?


Reply:

Subject: Maintainability
Reply Posted by: B.W.Dudley (bdudley@alionscience.com )
Organization: RAC
Date Posted: Tue Sep 3 14:32:00 US/Eastern 2002
Message:
It is not the usual practice to apply a safety margin to maintainability requirements. However, if one wants to have higher expectations of passing a test or demonstration, then application of a safety factor in the apportionment of requirements to lower levels would increase the design needs to make the unit more repairable. Note, the safety margin would be a lower value not a higher one as indicated. That is, the safety value for apportionment would be 3.5 hours not 4.5 for the 4 hour required level of maintenance.


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