Mist or smoke in vacuum chamber

[BrainChild]

Hello!

When pulling a vac on my chamber, within the 1st few seconds of evacuation I see what seems to be an oily mist forming inside my chamber. It's gone within a few seconds, but its been concerning me. The most I could find about this was on the skunkpharm page, in the comments on "vacuum purging and processing tips." It fear it could be what is referenced in the comments, "atomized pump oil backstreaming in to the chamber." This isn't actual liquid pump oil being aspirated into the chamber, I made that mistake long ago...this is actually coming from inside the vac chamber it seems. I only see it upon the initial evacuation of the chamber, at around 0-15hg, where the mist or smoke forms then is evacuated I presume, because I can no longer see it. But pretty much every time from pulling a vac from zero I see it.

I have a ball valve between my pump and chamber, I close the valve before shutting down the pump and start the pump before opening the valve. I also have my pump quite a bit lower than my chamber.

I just recently got a new vacuum pump thinking it might be the problem, a Robinair 15500 VacuMaster 5 CFM Vacuum Pump. I've been using just a 2 stage harbor freight pump. This happens with both pumps! :-\

Does anybody else see this too or know what is going on? I've been checking out foreline traps and check valves...but hoping somebody can help.


There are a few comments about this here: http://skunkpharmresearch.com/vacuum-equipment-and-process-tips/

I've copied this one that seems to describe it

"@tony, i just left a comment on the other version of this page (vacuum “purging” and processing tips) regarding this problem, its called backstreaming not to sure what allows this to enter the chamber itself but its caused by the vapor pressure point of the specific pump oil being used and during this vapor point the oil atomizes and has the potential to contaminate. Other than forline trapd there is not a lot of info on how the pump itself can keep this from happening, other than in my opinion from using a high quality pump that can be rebuilt if this oil breakthrugh happens ill i know its not the best of help but i certainly have concerns about this aswell and had to go to the right place to ask these?"

 

[kronus]

I have this same exact issue as well , when I 1st start pulling the chamber fogs up pretty bad and gotta keep exhausting until it doesnt fog up as much

Tried with 2 pumps as well and same issue

Anyone can help us??

 

[Gray Wolf]

I have this same exact issue as well , when I 1st start pulling the chamber fogs up pretty bad and gotta keep exhausting until it doesnt fog up as much

Tried with 2 pumps as well and same issue

Anyone can help us??

What is the humidity/dew point where you're at?

 

[BrainChild]

Where am at, humid as balls.

Or more specifically Dew point is 66° and humidity is 77% as I type. Could it just be water?

While trying to fix this recently I used some clear vinyl vaccuum lines, and I noticed upon pulling a vacuum and seeing this misty fog inside the chamber, tiny droplets of what seems to be water are forming inside the line directly attached to the chamber. It's a tiny amount and doesn't seem to be pump oil, which is what I was fearing it was. I don't see any fluid or anything in the line beneath the ball valve that isolates my chamber...

I'm glad kronus chimed in as well, I'm surprised others haven't seen this too. Because I've tried 3 different chambers and 3 different pumps now see this to some degree in all of them. I'm thinking of getting a foreline trap to be sure

 

[AOD2012]

I had a similar issue, except I noticed when I was done vaci'ing. I then realized that by leaving my pump running with the atmosphere side ball valve slightly open, it was sucking the pump exhaust in. Big mistake on my end. I know it's not the same, but I wanted to throw that out there.

aod

 

[Gray Wolf]

Where am at, humid as balls.

Or more specifically Dew point is 66° and humidity is 77% as I type. Could it just be water?

While trying to fix this recently I used some clear vinyl vaccuum lines, and I noticed upon pulling a vacuum and seeing this misty fog inside the chamber, tiny droplets of what seems to be water are forming inside the line directly attached to the chamber. It's a tiny amount and doesn't seem to be pump oil, which is what I was fearing it was. I don't see any fluid or anything in the line beneath the ball valve that isolates my chamber...

I'm glad kronus chimed in as well, I'm surprised others haven't seen this too. Because I've tried 3 different chambers and 3 different pumps now see this to some degree in all of them. I'm thinking of getting a foreline trap to be sure

That's muggy!

It could be the moisture attached to the inside of the chamber walls boiling off under vacuum.

You also decompressed the remaining moisture laden air in the chamber, which cooled it down, thus lowering the dew point, which might form clouds.

 

[cyphaman]

I get this sometimes too.

I always thought it was from outside my chamber until I started venting my exhaust outdoors and stilll seeing the smoke inside the chamber. Very odd.

I have a Brand New JB Industries 7cfm Platinum and 5 gal chamber. temps are low, and this only happens from time to time. Maybe an indicator of the need for an oil change?

I hate to say GW, but it looks much more like the pump exhaust than moisture clouds in my case. But not so sure myself... Thanks for your input here and to Brain child for bringing this one up!

 

[HashoftheTitans]

This just happened to me too. It started happening after our first rain in a couple months. It was very noticeable once it got muggy here. It happened in my chamber and my oven with different pumps. It's coming from moisture in the air IMO.

 

[JointOperation]

ive noticed this only when I don't do a long initial purge.. if I just blow my tane.. evap till it looks ok.. then toss in chamber.... this happens .. here and there.. but its only on the initial vac.. I wouldn't be worried about it .. but someone should post a picture of what the oil.. looks like when it gets pump oil IN IT..

 

[cyphaman]

i get this a lot now, might need and inlet trap, prevents oil mist from backfililng chamber.

just annoying, not affecting the product as far as I can tell.

 

[Chonkski]

I always just figured that the vacuum pulls the oxygen out first, and so fast, it leaves whatever percentage of moisture/humidity in the atmosphere there for to become visible for a second as mist/fog..(?)

 

[Young Bull]

I notice this all the time in my chamber, cold trap, receiving flask on my buchner funnel, etc.. I've always assumed it was from the vacuum pump oil. It honestly looks more like that to me. This is completely speculation but I've always assumed as the vacuum pump oil became more contaminated those contaminates would atomize and due to the strange dynamics in the chamber as the vacuum is being pulled it would somehow move over into the chamber as it was being purged and then pulled back into the pump as the chamber was more and more vacated.

I would feel a lot better if someone could prove to me it was just moisture from the air though.

 

[BrainChild]

Well it gives me some comfort that this isn't only happening to me, I really tried to find an answer before even posting this thread. At 1st I was convinced it was somehow vaporizing pump oil backstreaming up the lines.

Here is where I'm at now:

As I said before while trying to solve this problem I tried using clear tubing for my vacuum lines just so I could see what was happening and if any oil was being pulled from the pump. Well upon that initial vac, and seeing the fog...I always see little tiny droplets of a clear fluid forming on the inside of the lines, it's being pulled from inside the chamber and up the lines towards the pump. I only see these droplets on the side of the lines connected to the chamber. Also, at the same time I see those little droplets, a small amount of moisture is condensed onto the OUTSIDE of the lines too. I see this moisture around the same spot I see the inside droplets (right around where the tubing connects to the chamber) And the moisture on the outside is quite cold when it condenses. Something seems to be happening with the dew point, as GW describes.

The little droplets on the inside the line get sucked up towards the pump and disappear after a while, but I've disconnected the lines while I can still see the droplets and wiped them out with a q-tip and have inspected it to no end...it's not oily at all. It really is just water I think. I've rubbed it between my fingers and smelled it...it doesn't have the smell and feel and pump oil. More like just water.

I'd bet anybody else seeing this fog, if you had clear vacuum lines you'd see the same thing. I know a foreline trap will prevent any backstreaming of oil, so that is an option. Also a check valve perhaps. I'd like to try something like that, but as of now I'm fairly comfortable saying it really is just moisture laden air in the chamber as GW describes.

 

[BigJohnny]

First, It would be impossible for oil to come out of the pump through the suction side and get into the oven. That just isn't how pressure differentials work.

The vapor you see is the butane/alcohol/whatever vapor of what's boiling in the oven. Any moisture in the air would also evaporate and turn to vapor. As you increase vacuum, you decrease boiling points.