Looking for a reliability-type formula
Looking for a reliability-type formula
(OP)
Hi guys
I'm working on a project and I'm trying to put together a cost analysis for some items. I remember in University handling similar problems, but I don't remember the methodology.
Here is what I'm trying to do. Given:
- The age of the unit (say, 1989, so 18 yrs)
- The expected useful life (say 30 yrs)
- The number of units (say 10 units)
- Some accuracy percentage (say 95%),
- some time interval (say, the next 5 years)
I'd like to be able to CALCULATE that X number of units of my 10 are 95% likely to fail within the next 5 years.
thanks everyone.
dan
I'm working on a project and I'm trying to put together a cost analysis for some items. I remember in University handling similar problems, but I don't remember the methodology.
Here is what I'm trying to do. Given:
- The age of the unit (say, 1989, so 18 yrs)
- The expected useful life (say 30 yrs)
- The number of units (say 10 units)
- Some accuracy percentage (say 95%),
- some time interval (say, the next 5 years)
I'd like to be able to CALCULATE that X number of units of my 10 are 95% likely to fail within the next 5 years.
thanks everyone.
dan





RE: Looking for a reliability-type formula
Hi Dan,
Not sure about your question but perhaps a life cycle costing analysis will provide a better financial picture.
+R
RE: Looking for a reliability-type formula
But, in any case, without some additional data, I don't see that you can your desired answer. Prognostication is horrifically non-deterministic. You need to know hours-on, operating temperature, vibration environment, etc, to come up with a mean value, but even then, you'd need statistic history to know how much variance there is in the actual times to fail.
TTFN
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RE: Looking for a reliability-type formula
And we'll make up a confidence interval, say 99% of units have an expected useful life of 30 years.
My gut says that Poisson can be modified to solve for this type of problem, but its been 8 years since I did any real probability problems.
With regards to accuracy, we have some flexibility since this is not a life safety issue. If we say that we are 95% confident that 4 units will fail, and instead, 5 fail, it is acceptable to attribute the variance to a poor maintenance program.
Thanks everyone for your help.
RE: Looking for a reliability-type formula
TTFN
FAQ731-376: Eng-Tips.com Forum Policies
RE: Looking for a reliability-type formula
If so, what is it?
RE: Looking for a reliability-type formula
h
Hope this helps!