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: Stephen Deneca
Date posted: Mon Mar 5 15:33:44 US/Eastern 2007
Subject: MTBUR vs. MTBF
We have a new product being developed that an MTBF report was generated for. 217f hours=50,000. Our customer wants to know what the MTBUR rate would be. Does anyone know a way to correlate the two?
Subject: MTBF vs. MTBUR
Reply Posted by: BWD
Date Posted: Mon Mar 5 17:00:22 US/Eastern 2007
MTBF (mean time between failures) calculations count all failures and failure modes in the assessment of unit reliability. MTBUR (mean time between unscheduled removals) calculations count only those failures that require removal of the failure item. So, the way to correlate the two methods is to review the components, the failure modes and the modes of operation. The next step is to determine the failure rates for those components that do not affect unit performance or only degraded slightly, such as, indicator lights, surge protectors, redundant fans and other similar components. This failure rate sum would then be subtracted from the unit (1/MTBF) failure rate to determine the removal value.