Hey community! So here’s the deal. I have 2 20L short paths doing runs today. Same material, only one run was ran thru a wiped film and reran in a spd to pull the remaining cbd from the raff. The 2nd run was a fresh 1st pass. Both systems have independent vacuums with fresh oil. One system is brand new, 1st run on it and the 2nd is only a couple weeks old. Both systems deadheaded at under 100mic. Start both runs within 2 hrs of each other. When each got up to temp and time to start the stir bars that’s where shit gets funky. As soon as I turn the stir bars on my vac jumps from 200-400mic to over 1800mic. I’ve taken apart both systems and thoroughly checked for vac leaks. When I turn the stir bar off my vac goes back down to normal range for the time of the run. Turn it on and it jumps right back up. This is going on 6hrs+ into the runs. At this point I’ve done hundreds of runs and this is the 1st time I’ve had this issue and it’s happening on 2 spds at the same time on the same day. Can someone please help me before I lose my mind…
Pictures and details would help.
Full bore? Vacuum pump type and model? CFM of vacuum pumps (you will need at least 30-40 CFM for a 20L setup)? Vacuum oil used? Temperature you are getting stuck at? Decarb/devolatilization temp? Amount of oil loaded in?
Dead heading at 100 really is not a good starting point, from the limited I fo it just sounds like you don’t have enough CFM.
What’s the mantle temp when you turn those stir bars on?
Does it go back down, my gauge jumps when i turn it up but then goes back down. Definitely not anywhere near that micron
You’re likely running into vapor pressure being released by the stir bar. When it moves it’s releasing vapors which otherwise won’t move until they bump. Since the environment is under vacuum you no longer have convection working in your favor to help move the vapors. You should see your vacuum fall with time as it defeats the current fraction.
This issue is happening all the way to tails with one of the runs. This is a 20L full bore system. I started a new run myself today to make sure it wasn’t one of my guys putting it together incorrectly. I cleaned all joints w acetone prior to vac grease. I added another Edward’s 28 to see if that may have been an issue but still going on w 2 vac pumps. I noticed some vapor trails when getting up to about 140c. So I turned the heat off, let it cool down and broke vac. Took everything apart, cleaned w acetone again, regreased the joints reassembled and once again got to 140 and still vapor trails. It has to be a vac leak but in hundreds of runs I’ve never had one that I couldn’t correct. I feel like I’m doing runs on a 2L monocow spd w leaky hoses and no vac gauge again… I’ve had one of the 20L setups for 3 weeks without this issue the only difference is the boiling flask. One of my guys broke 2 in 2 weeks and I bought these from a maker of american glass ive used in the past without any issues. That’s the only variable I can think of and it’s when this issue began.
Im at 150c
Wow. I only have a 10L full bore, but my mixing bar is turning as soon as whatever it’s sitting in is warm enough for it to turn. I have to imagine with a 20 there’s a Lot of crap that hasn’t made it out of there without any mixing. It’s probably creating plenty of vapor pressure when you turn the stir bars on. Try it again with those turning as soon as it’s warm enough for them to turn. I’ll bet it makes a big difference.
as people have said, it sounds like you havent properly degassed your material. your stir bar is agitating your solution kicking out lites (trace amounts of volatile molecules)
I could use a few pump suggestions for my 20L 2 head full bore short paths. Say I had an unlimited budget what pump combo should I go with and also what combo on a midrange to shoestring budget… As always the feedback is always appreciated. Thank you
Roughing pump, e30 , diffusion pump in that order. All can be done on a small budget or you could spend alot and get newer bigger badder.