Re: Cooling fans and projector lamps

[P3D KENNETH LUKER <KLUKER@xxxxxxxxxxxxxxxxxxxxxxx>]

>The quartz cools too quickly if the fan is left on after the lamps 
>have been on a while. This causes small cracks to form. These are 
>many times visible to the eye. After a number of these fast heat-
>cool cycles, the envelope springs a leak and oxygen enters the 
>envelope. IT won't take long after that for the lamp to burn out. 

That makes sense, but what about the sudden heating when the lamp is 
turned on?  Doesn't the rapid heating phase cause as much or more 
thermal stress as a rapid cooling phase?  It certainly is of shorter 
duration than the cooling, with or without fan.  It would seem that 
the life extension due to turning the fan off when the light is 
turned off would be very minimal compared to the life extension that 
might be possible if there could be a slow heating phase at turn-on 
time. Of course in the limit, if one never heated the lamps at all 
(kept them turned off all the time) the life extension could approach 
being infinite. :) :) 

Ken Luker_______________________________________________________________

Kenneth Luker, Assistant Director
Systems and Technical Services
Marriott Library
University of Utah
Salt Lake City, Utah
KLUKER@xxxxxxxxxxxxxxxxxxxxxxx


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