Sulaiman
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Advice on protecting a vacuum gauge wanted
A member of a different forum that I frequent ( 4hv.org ) asked the following question;
"How can i protect my new digital vacuum gauge ? i typically have a vessel pulled down to high vacuum with epoxy, oil and other liquids which might
volatize."
Any suggestions ?
CAUTION : Hobby Chemist, not Professional or even Amateur
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wg48temp9
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Quote: Originally posted by Sulaiman  | A member of a different forum that I frequent ( 4hv.org ) asked the following question;
"How can i protect my new digital vacuum gauge ? i typically have a vessel pulled down to high vacuum with epoxy, oil and other liquids which might
volatize."
Any suggestions ? |
The usual way its done is by an isolation valve and preferable a cold trap. The gauge being isolated until the roughing pump has exhausted most of the
gases and closed before releasing the vacuum. He should consult the manual for the gauge if its an expensive one.
He should also note that the type of vacuum gauge determines how susceptible the gauge is to spurious vapours. Typically gauges with hot wire or
filaments are more susceptible. He should also note that if he does have volatile material in his system he will not be able to reach a high vacuum
(mean free path comparable to the dimension of his chamber).
An other option is to have a discharge tube connected to the system. The characteristics of the discharge indicate the vacuum level and the discharge
color will give an indication of the contamination. When the discharge goes dark under vacuum the mean free path is about equal to the separation
distance between the electrodes. ie high vacuum.
The discharge also helps to trap or destroy active gases. It can also help when trying to find leaks using a suitable gas or fluid sprayed on to the
suspected leak point.
I am wg48 but not on my usual pc hence the temp handle.
Thank goodness for Fleming and the fungi.
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Sulaiman
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Thanks
Information passed on.
CAUTION : Hobby Chemist, not Professional or even Amateur
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S.C. Wack
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There are chemical traps as well (charcoal, zeolite)...more for the protection of the vacuum pump post-cold trap...when valves are used they are often
between the pump and gauge, for when the pump is to be turned off.
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Sulaiman
International Hazard
Posts: 3558
Registered: 8-2-2015
Location: 3rd rock from the sun
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Thanks, it seems that the query has been answered satisfactorily
CAUTION : Hobby Chemist, not Professional or even Amateur
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