In a message dated 5/6/2005 1:21:48 A.M. Eastern Daylight Time,
robert.hedan@... writes:
How can you pull the vacuum down 2 atmospheres? Assuming I am at 1
atmosphere, isn't 0 a vacuum? Or did I miss something and you can a bigger
vacuum? Huh? How can you go to negative atmosphere? I thought atmospheres
were mostly used for pressure chambers.
I often see reference to 0-30Hg for vacuum chambers, something about mercury
level. I figure I'll see where the vacuum dial sits at rest, and where it
goes as air is pumped out is the vacuum side.
Robert
:)
Most vacuum is measured in HG which is mercury. being so heavy you can use a
much smaller scale! Now if I remember my old school books normal atmosphere
at sea level is about 15lb's per sq inch. Now 2 Ats. would be 30lbs per sq
inch. No go to vacuum and the same applies but in the opposite. So 30HG vacuum
would be 2 Ats. When I do A/C work this is the standard test we do. Draw down
to as close to -30 hg and cap it off. wait 1 hour and see if we have any
leaks then charge the system.
If I did not get any of the math right I am sure someone will jump in and
correct it! High school was a long time ago! LOL
Just putting the mold under 1 At or -15lbs of vacuum will do the job you
need to do!
Ray Russell
NMRA-40609
General Contractor
Norfolk & Western Railroad
Pocahontas Division
Circa 1958
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