Sciencemadness Discussion Board

Advice on protecting a vacuum gauge wanted

Sulaiman - 27-10-2019 at 01:17

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 ?

wg48temp9 - 27-10-2019 at 03:52

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.

Thanks

Sulaiman - 27-10-2019 at 06:14

Information passed on.

S.C. Wack - 27-10-2019 at 08:51

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.

Thanks, it seems that the query has been answered satisfactorily

Sulaiman - 27-10-2019 at 17:41