Hello to kpkelly!
Since you operated your machine when you lived at sea level I can
tell you are probably quite knowledgeable on how to use your own
machine. I have a moment to address your question. I operate a
shop where my specialty is my ability to repair every piece of
equipment a jeweler uses and I have designed casting machines during
Vacuum pumps work the same regardless of altitude. If your machine
is located at 6500 feet or 6900 feet as we have here at our shop the
pump actually has a “head start” on pulling as complete a vacuum as
it is capable of. The need of the vacuum pump is to attain nearly
It sounds as though the most likely difference between your sea
level experience and your high altitude experience is that during
the transition, your system may have developed leaks or water may
have already damaged parts of the pump causing the inability to draw
sufficient vacuum for your work. Please check your system for
There are 2 ways to measure your vacuum : (1) compare the vacuum
chamber to atmospheric pressure; this is what the gauge on your
machine does (2) measure absolute vacuum…(the gauge on your
machine is using the comparing vacuum pressure to atmospheric
pressure method because it’s easy and inexpensive).
We test vacuum pumps here in our shop using the more expensive
"AbsoluteVaccum" gauges and we require casting machine vacuum pumps
to test between 50 and 100 microns before we consider them truly
repaired. Traditional differential pressure gauges just don’t have
the necessary resolution to measure vacuum down that far.
For most of your casting needs you’ll be relying on a combination of
normal gauge readings and your skill and experience to get the
results you need.
Our philosophy on maintaining vacuum pumps is to drain the water and
the old oil; fill with new oil; as often as you can afford to do
so–we recommend draining and filling about once a month with
regular usage and more frequent is better of course. Two important
things (1) maintain the proper level of oil in the pump (2) don’t
let the pump sit for very long with water in the crankcase.
Our philosophy, based on many vacuum pump repairs and “rebuilds” is
that the only thing that should be put into a vacuum pump crankcase
is good quality, fresh, vacuum pump oil – (sometimes we see other
things which people put in the crankcase such as cleaning solvents,
trapped in pockets near the bearings and the seals, which increases
the frequency of problems, thus the need for repairs. Good quality,
fresh, vacuum pump oil will result in the best performance and less
frequent need for repairs. Vacuum pump oil is considered as just
one of the many materials consumed in the process of casting.
I wish you the best of luck and if you have more questions you may
email me any time. Best Regards, JOHN CRANOR, The Jewelry Equipment
Dr (web address)= members.aol.com/johncranor