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From: Michael Schwingen <news-1513678000@discworld.dascon.de>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: Pi-FAN for RPi4 with 4 (instead of 3) cables?
Date: 10 Dec 2024 19:30:23 GMT
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On 2024-12-09, The Natural Philosopher <tnp@invalid.invalid> 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-mtbf-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.