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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: Bryant
Date posted: Fri Dec 6 8:51:22 US/Eastern 2002
Subject: MTBF for complex electromechanical system
I just want some advice on which distribution should i use to model complex electromechanical system for example army vehicle? Some advice me to use exponential distribution. Can advice? Secondly MTBF only applies to exponential distribution but in actual fact, the vehicle will wear out sooner or later. So for my spares provisioning model should i use MTBF or MTTF values to be more realistic?


Subject: MTBF for complex electromech system
Reply Posted by: C. Jayaraman
Organization: Raytheon
Date Posted: Fri Dec 6 12:54:20 US/Eastern 2002
Bryant: Using exponential distribution will be conservative and and also will depend on the amount of mech items as a proportion of the overall system. I would be tempted to go with real life test data when possible. For spares/ provisioning use MTBF and use about 40% of predicted value since new systems take some time to settle down. Also all spares and provisioning formulas use poisson although in some cases erlang distribution have been used. Approximations will suffice since all fractions will be rounde up. Good luck.


Subject: No field data
Reply Posted by: Bryant
Date Posted: Sat Dec 7 21:59:54 US/Eastern 2002
The fact of the matter is that we could not obtain field figures during developmental stage and we're supposed to recommend certain spares package upfront. As a common practice in my organisation, we are using the MTBF figure in our analysis and i'm wondering if this is the correct approach?

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