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: Cloarec
Date posted: Mon Mar 10 9:15:08 US/Eastern 2003
Subject: MTBF and TBO
I need some explanation. I have a system whose TBO is 20000 hours. One guys find that the sytem MTBF = 18000h. So he would like to have a MTBF greater than TBO (he says that he don't want a failure at 18000 that need repair because it missed 2000hours to go to the TBO). I tried to explain him that there is no relation between MTBF and TBO. Have you some practical answer to explain this ?
Subject: TBO and MTBF
Reply Posted by: bwd
Date Posted: Tue Mar 11 9:43:47 US/Eastern 2003
Given that term, TBO, stands for time between overhauls, I would state that this term relates to the end of life failure modes. This interval relates to the time when wear-out of items start to occur. The MTBF [mean time between failure] term relates to the probabilistic condition of failure. That is, MTBF is related to the number of chance failures in a given period of operation. The probabilistic situation is one that failure could occur at any time during the operating period or not occur at all where end of life failures are predictable at a specific space and time. The TBO value has no direct relation to the chance failure rate as its function is to determine the time to renew the unit from wear-out failure modes.