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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Posted by:Jim Guzzio ( )
Organization:General Dynamics ATS
Date posted: Mon Sep 18 10:44:01 US/Eastern 2000
Subject: "Merged Failure Rate" Calculation
With respect to the "RAC Data Failure Rate Selection Screen," the User is only able to filter on the Part Type First, Second and Third-Level Modifiers, i.e., there is no provision for filtering on the absence or various combinations of these modifiers. Since the User does not have the ability to select just those rows in the table which he/she wishes to retain for determining the "Merged Failure Rate," it would be helpful to have the ability to perform this task externally. Unfortunately, the methodology required to do this does not appear to be contained in the documentation.


Subject: "Merged Failure Rate" Calculation
Reply Posted by: David Dylis ( )
Organization: Reliability Analysis Center (RAC)
Date Posted: Wed Sep 20 8:59:10 US/Eastern 2000
It appears that your question deals with the RAC PRISM reliability assessment software. When developing PRISM we chose to limit the use of RAC failure rates from NPRD and EPRD sources to a merged failure rate value to improve the confidence of the value used in a reliability assessment. I agree that the methodology that is being used by PRISM to merge this data should be included in the PRISM user manual and help. This information will be provided in a future PRISM update. The technique that PRISM uses is the same technique used by the RAC when merging data in our data books (NPRD and EPRD). Since formulas and equations are not easily provided through this forum, it will be necessary to fax that information to you. If you have a copy of NPRD 1995, the methodology is described on page 1-16.

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