Hi IRstuff,
Maybe I've misunderstood you or vice versa, but I agree with what you've laid out in your last post. That is precisely what I have done and another quick check on the internet has also confirmed the methodology I believe ...
Hi IR Stuff,
I don't really follow what you mean. How else would you be able to determine an overall MTBF without converting the MTBF's to FR's prior to summing?. One ultimately ends up with an overall FR, which logically could be converted to an MTBF.
Cheers,
KB.
As an aside, something else that I have been uncomfortable about is I have been estimating MTBF's for various vehicle system during trials.
If for example a vehicle has accrued a total of 4000 trials miles and has had say, 2 failures I have estimated the FR as 2000 miles MTBF for that system...
Thanks for your replies. I agree, you can add failure rates and multiply reliabilities. However, an MTBF is the reciprocal of a failure rate I wasn't sure if you could therefore add them too ! As mentioned though in my initial post it just didn't sit well with me and when I look back through all...
OK. First post and quite a simple query, that I really should know but something just doesn't sit well with me !
Is it acceptable to simply add sub-system MTBF's together to obtain the overall System MTBF ?
Eg.
A = 3000 miles MTBF
B = 2000 miles MTBF
C = 4000 miles MTBF
System MTBF = 9000...
