Does humidity change vacuum

[smiao]

I have a process that involves picking up a 3/16"x30"x60" piece of glass with a small vacuum system. Recently we have experienced a situation where the glass falls from the device. We currently have very high humidity and I am curious if vacuum increases or decreases as the humidity increases.

 

[IRstuff]

> But, there are way more other things that correlate with high temperatures besides RH. Many of those are probably more of an impact on performance than RH.

> I don't think that the pumped vacuum (dynamic) is the same situation as a low pressure (static). In the latter case, it's the partial pressure of water at a given temperature that drives the amount of water vapor. So, unless there's liquid water, the partial pressure cannot be sustained. In the former case, the pressure is being actively maintained, and there is a concentration gradient that drives diffusion of molecules toward the pump. This is independent of the partial pressure question, and the other other molecules in the system can also steer the more recalcitrant molecules towards the exit. This mode is similar to that of a high-vacuum diffusion pump, where hot, vaporized oil essentially drives gas molecules away from the vacuum chamber towards the mechanical pump.

The mechanical pumping process, be it diaphragm, scroll, or turbo, is mechanically unaware of whether a molecule is water, or not, and will pump it away. That said, it might be possible that water intrusion into the pumping mechanism might degrade its pumping efficiency.

TTFN

FAQ731-376

 

[moltenmetal]

Good that your problem seems to have been solved.

It seems to me that the lift/hold force this system is capable of delivering would be proportional to the pressure difference between the atmosphere and the inside of your vacuum system. If you reach 1/10th of an atmosphere in your vac system, you've achieved 90% of the lifting/holding force you'd achieve at full vacuum. A little condensed water inside the equipment/tubing might drop your maximum achievable vacuum to the vapour pressure of water at room temperature (~ 0.03 atmospheres), but that wouldn't make much difference on your ability to lift.

A little liquid water WOULD make a HUGE difference in your ability to achieve a high vacuum, like the one you desire in a tubing system prior to filling it with refrigerant!