@Thomas
The pump is new. Is a break-in period required before the best vacuum is reached. Right now, I only have about 2 hrs running time on it.
Bruce
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--- In VacuumX@..., Thomas Janstrom <t_janstrom@...> wrote:
Have you baked the fittings sensor etc. while pumping down? Might get
you a bit further down, but if it's holding vacuum then it's not going
to be the magic bullet.
Oh yeah is the pump brand new or older?
Thomas.
On 8/09/2011 11:33 PM, trikeflight wrote:
Thanks Gomez --
FYI, I bought a Viot 2-stage rotary vacuum pump (2.75 lpm) for some
plasma experiments. To check out the pump's ultimate performance, I
mounted a TIF9450D Digital Micron Gauge directly on the pump's 3/8"
brass input port (with an isolation ball valve). With fresh oil and
clean brass fittings, I am able to pump down to about 200 microns Hg
after several out-gassing cycles lasting about an hour. It appears
that 200 microns is the floor for this setup. With the ball valve
shut, the small sensor chamber leaks only a few microns a day, so I
know I have a tight chamber. This pump has an "ultimate vacuum" rating
of about 15 microns, so I am trying to determine if my mediocre vacuum
level of 200 microns is due to my inexperience with vacuum systems or
if this performance is "normal" for an inexpensive 2-stage rotary
vacuum pump. Comments and suggestions are welcome.
Bruce
--- In VacuumX@... <mailto:VacuumX%40yahoogroups.com>,
Gomez Addams <gomez@> wrote:
On Sep 6, 2011, at 9:57 PM, trikeflight wrote:
The specifications for several two-stage, rotary vacuum pumps list
an "ultimate vacuum rating" of around 15-20 microns Hg. Has anyone
come close to these vacuum pressures with one of these commercial
pumps? If so, what pump make/model and what type of pressure sensor
did you use?
From my limited experience and a lot of reading, those ultimate
pressures apply to a brand new pump fresh from the factory, with brand
new oil of the best available sort, dead-headed with a sensor at the
port (obviously).
And it will only do that after perhaps a hundred hours of break-in,
but only for the first 1,000 hours of operation maybe much less
depending on the design.
This is kind of a hand-wave estimate from memory tho. Why? Do you
want to try to achieve a moderately high vacuum without a high vacuum
pump? Doing so nearly always puts you on the edge of the mechanical
pump's performance, and will lead to tears as soon as it no longer
performs at its peak.
