Dear Lab Guy,
we are using an SP Bel-Art Space Saver Polycarbonate Vacuum Desiccator in the lab. I was wondering what the maximum applicable vacuum is? The manual said it hold 14 psi for 24 h but does it mean it is the max it can withstand?
All of our vacuum desiccators can hold the equivalent of one negative standard atmosphere.
This picture shows a vacuum pressure gauge in one of our Lab Companion Desiccators showing measurements in Mega Pascals (MPa). The greatest measurement (at the 7:00 position) is -0.1 MPa, which is considered the limit of vacuum capable in a laboratory using standard vacuum sources. The negative sign is assumed since we are talking about vacuum pressure or negative pressure.
This is the value I mean when I mentioned one negative standard atmosphere above.
The unit equivalents of pressure, in different units, are as follows:
Standard Atmosphere = 1
KPa = 101
MPa = 0.1
Torr = 759
Bar = 1
In Hg = 29.9
Mm Hg = 759
PSI = 14.7
In other words, your 14 PSI is the uppermost limits of not only the chamber, but also the vacuum you would be able to generate in a normal laboratory. This is also the amount of vacuum pressure used in nearly all laboratory desiccators. Your 14 PSI is right on mark!
I hope this helped and answered your question. Thanks for writing in, and please feel free to write back if I can help in any other way.
Yours in science, Lab Guy