You haven’t described two important factors: do you have an effective (dry ice cooled, eg: dewar) trap in front of your Welch, and where is your vacuum gauge located? I always use two convection ( physics guys calm them ‘Convectrons’) gauges that read down to 0.0001 mm Hg. One at the pump, and a second as close to the ‘apparatus’ as possible. There’s always higher pressure at the system than at the pump, so the difference between the two is a good indication of flow. Also I would not use rubber hose anywhere in your setup. Wire-reinforced pvc is the preferred material, and use as little as possible. These mods should get your system under 100 mTorr and get your temperatures down. That trap in front of the pump is crucial to prolonging the use of pump oil and vacuum performance.
Yes ofcourse I run a cold trap. 2 of them in fact. Both Dewar style. My vac gauge was purchased from across international and reads digitally 00.000 in hg and reads many other measurements aswell. My vac gauge is placed after the last Dewar condensor and before the pump. I was under the impression the gum rubber tubing was the best to be used? Which is what I use and why. I only use rubber tubing for the water in the condensor.
If your vacuum gauge bottoms out at a reading of 0.001 in Hg (inches of mercury), that’s 0.025 mm Hg (25 mTorr). That’s not enough low-end resolution for this application. Your Welch 1400 is rated to pull as low as 0.1 mTorr, and most direct-drive pumps (with fresh oil) will pull between 7 and 20 mTorr. You won’t see those levels with your gauge.
Gum rubber tubing is pretty old-school. It will tend to absorb terpenes, which contribute to “background,” or in other words, eventually you will not be able to pump below whatever the terps’ aggregate vapor pressure is. The wire-in pvc is now in general use in instrument applications, and has the added advantage of transparency: when it starts to get fouled, you can at least see the material building up, and either remove to clean, or replace. Gum rubber doesn’t give that added clue that it’s outlived its life.
I replace all my lines every run. So you think it’s necessary to be able to read my vac below 29.999? The extra is really going to make a difference? As i paid about $1200 for this gauge/regulator and hate to replace it unnecessarily
use it in conjunction with a pirani gauge, that way you have two guages you can compaire readings from.
Could you send me a link to purchase from a reputable seller?
If you use a computer you can hook up a 60$ gauge to the serial port its the mks 901p… I wouldn’t do it unless you are a little computer savvy, but otherwise you are probably looking upward $1000 - $3000 for a gauge and controller that are reasonable.
Long shipping time on the vac oil and flushing solution from the site above. I’ve ordered some of the tubing with the wire aswell . Im anxious to see what my pump will get down to after these changes, dang shipping times!
If you decarb before SPD, you shouldn’t have a lot of foaming. I would pull full vacuum before applying any heat to the mantle. This also lets you check for leaks in the system. Make sure your cold traps are cold before doing this.
Also, you could be running a much hotter condenser, minimum 80C.
Get your winterizing under control, hotter condenser, full vac through volatiles, and you should see an improvement.
If you see smoke, oxygen is getting into the system somehow.
If you can go full bore, you should. I found that switching to that and adding a thermowell and stopper aswell as temp wire probe between the mantle and bf allowed for me to pull down to blank off values in an empty system and below 100 micron midrun.