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 Message 21140 
 Michael Schwingen to The Natural Philosopher 
 Re: Pi-FAN for RPi4 with 4 (instead of 3 
 10 Dec 24 19:30:23 
 
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On 2024-12-09, The Natural Philosopher  wrote:
>> https://www.rs-online.com/designspark/why-l10-life-expectancy
is-key-for-fan-durability-over-mtbf-ratings
>
> This is full of bullshit
>
> "MTBF estimates the lifespan of a fan’s electronic components, expressed
> in millions of hours. In contrast, L10 Service Life, measured in
> thousands of hours, is based on the durability of the bearings and
> lubrication grease."
>
> So a fan with no electronic components has no MTBF?

remove "electronic" and it makes sense.

>> https://www.digi.com/support/knowledge-base/understanding-mtb
-mean-time-between-failures
>>
>
>
> "Furthermore, MTBF specifically excludes wear-out factors"
>
>
>   Total crap.

No. Again, MTBF characterizes failures during normal service life.

Take a fan which usually fails after 5 years of operation due to wearout,
which happens on all of those fans after about the same amount of time -
those 5 years are *not* parts of the MTBF.  MTBF characterizes the
statistical mean time between failures *during* those 5 years due to *other*
reasons.

So you can have a MTBF of 50 years, and a lifetime of 5 years. If you take
100 of those fans, you can expect 2 failures per year - but after 5 years,
the failure rate will rise rapidly to reach 100%.

> What matters is how long the repair or the new fan will last. Not
> splitting hairs over MTTF versus MTBF

The important thing is to keep MTBF and lifetime separate - both will lead
to failures, but are separate mechanisms.

cu
Michael
--
Some people have no respect of age unless it is bottled.

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