SRC Forum - Message Replies
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
Posted by: GR Gibbons
Date posted: Fri Apr 16 15:57:35 US/Eastern 1999
Subject: Reliability Modeling
Parallel reliability models described in Mil-Hdbk-338-1A refer to redundant items. What is the equation for a 5:1 model, i.e., 5 non-redundant items with the same failure rate and 1 hot spare for all five? If it is the same as the K out of N configuration model which is in terms of availability, what is the equation in terms of the failure rate?
Subject: Redundancy Modeling
Reply Posted by: Bruce Dudley
Organization: Relaibility Analysis Center
Date Posted: Mon Apr 19 14:09:01 US/Eastern 1999
The redundancy formulation that I would follow for the 5 units active and 1 unit "hot" standby is the binomial configuration for all energized, all equal reliability, perfect switching and non repair. From the Reliability Toolkit, Commercial Pracytices Edition one can develop a 5 of 6 reliability function which is: (6 exp(-5 lambda t)) - (5 exp(-6 lambda t)). Integrating from 0 to infinty, one gets an MTTF of 11 /30 lambda.