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Confusion Pumps

Hi Dave,

 Nice to have you back.  How was Italy?  Did you show them all of our posts?

 >> I've seen very successful use of large vacuum rubber on the high vac. side
of the system as the main "stopcock". A lever attached to a bar closed and
opened the system by compressing the vacuum rubber. This system,with a 3 stage
diffusion pump was designed to pump 8 @ 8' 25mm lamps at a time. I've seen
very old lamps that this system produced and no question the man who pumped
them was a master. <<

 Gee, I wonder who that could have been?  Since I am using the pump you are
referring to I'll set the record straight. It is actually a 2 stage aspirator.
Looks like the normal single stage aspirator you can get from most neon
suppliers but has an additional stage I like to call a pre-amp stage. (Sorry,
another term borrowed from Audio)  Anyway, the additional section is a down
sucking, sideways pushing arrangement that starts the molecules heading toward
the venturi of the normal aspirator section.  It has an additional heater
under it the same as the normal section and the boiler sections are connected
by a small diameter (6mm) tube to allow the silicone fluid to equalize between
the two sections.  It does a hell of a job at pumping (sometimes TOO good).  I
went to the Corning 705 fluid because it gets to a higher ultimate vacuum and
it is also SLOWER than the 704 fluid which I still like better with the single
stages.  I have an OLD, OLD Cenco MegaVac pump as the roughing pump and it
seems to be a good system together.  Got lots of Chuck stories but later on
that.... I have to admit, I learned a lot about pumping from him.  BTW, in
order to make those tubes you described those pumps had overcome a TON of dirt
in his system (including the pumping fluid that I don't think he ever changed
in 20 years), the rubber "valves" you described and some micro-leaks in the
pyrex on the pump where it was repaired once. I'm still chasing those. I think
it was cleaned with steel wool.  BTW, don't ever clean glass you intend to
heat up again with steel wool unless you can thoroughly wash off the
micro-residue. If you ever want to get back at someone give him some glass
like that.  You will never get out all the leaks.  I learned the hard way.  I
once built a manifold out of glass I cleaned that way.  I threw it out and
started over. (After I figured out what the problem was).

 I any of you are planning to come to the shop on Dec. 1, you will see the
pump. I am sure it is much better to see it than to describe it.   You can see
the part I am describing if you have that article from the Oct. '95 issue of
Sign Business Mag. (They cropped off the "normal" part of the aspirator). It
is under the table to the bottom left on page 17.




  E-mail from: Tom Biebel, 23-Nov-1995
 

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