On Apr 26, 2005, at 3:13 AM, Steve Thompson wrote:
> On Tuesday 26 April 2005 10:51, G3rzp@aol.com wrote:
>> ....... The problem
>> turned out to be a ball race in the three phase fan of a humidifier,
>> which
>> had seized after only 3000 or so hours. The situation was was
>> exacerbated
>> because Boeing had managed (quite accidentally) to fit a 25 amp
>> breaker to
>> protect wiring rated at 4 amps, instead of a 2.5 amp breaker. Now if
>> aircraft quality bearings can fail that soon, what does it say for
>> cheap
>> fan bearings?
>
> I'm with you on cheap fans. On the other hand, in 1990 I build 16
> class A
> amplifiers for a tunnel distribution system - they dissipate 150W
> continuously and needed fan cooling. I chose a Papst 24V ball race
> 100cfm fan
> for the job. They have been running at 28V 24/7 since late 1990 with no
> failures yet. I recommended replacement every 5 years and designed the
> units
> to allow that without interrupting operation, but the customer decided
> it was
> acceptable to wait for failure before replacing.
Panasonic (Matsushita) makes fans that use "surface-wave" oilite
bearings. As I recall, the life expectancy of them is c. 4x that of
ball-bearing fans.
>
> I think it's over 120k hours continuous, and about 2m hours
> accumulated so
> far. I'm also pleased that none of the amplifiers have failed either.
>
> Steve
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
>
Rich Measures, 805.386.3734, AG6K, www.somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|