what is a T?
A metal fitting wit 3 exits in the form of a T
The straigt line to the pump and on the leg
The valve
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Hello, all! Iāve just set up my 5L SPD kit, and Iām trying to reach the appropriate vacuum depth.
My first vac down reached 300 microns, which I thought was pretty good, but Iām aiming for <100, so I checked all of the greased joints, wiggled the hoses, etc, but could not get any lower.
I added gas-rated Teflon tape to the glassware threads for hose hookups, as well as the thermometer probe before the O-ring, but then I could not get the system below 900 microns.
Grabbed hose clamps from the local hardware store to put on the connections, and then couldnāt get below 1,600 microns.
I removed the Teflon tape, cut the hose lengths, but kept the clamps, and this morning, I got it down to 510 microns for a few minutes before it steadily bounced back up to 1500+ microns.
The vacuum pump oil was changed just a couple days before this, and now Iām out of it, but more is on the way. Iām racking my brain to think of what else could be the issue, if itās not the pump (Vevor 2-stage 12CFM continuous duty)
Any advice from more experienced operators? Pics of my setup included below.
You need a better pump man
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You need to shorten all the hose work by about 80% too.
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Dual cold trap = lower vacuum
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But thatās really isnāt as necessary as a new pump and much shorter hoses. Seems like the rest will work. A different vac gauge couldnāt hurt either.
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I mean I like 5 micron or lower. 
While full
Can also fully cover cold trap RF with dry ice. Knock down a few more microns of vac level.
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so did you actually test where the pump could pull to with nothing but the gauge on there?
thatās known as your blank-off value.
no point on sucking forever trying to get to sub 100 microns if you havenāt demonstrated the pump can get there without your (presumed) leaks.
one youāve proved (or disproved) that, you know if youāre looking a leaky gear, or a junk pump.
yes, that is a junk pumpā¦but Iāve seen worse get the job done. with tight glass.
didnāt see that!
youāre not getting 12CFM through that itty bitty tube.
folks killing this trick open up that vapor path to 1" or so. all the way back to the pump.
you donāt want that gauge IN your vapor path.
just measuring the pressure in said path.
What sort of tubing is that.
does it collapse when you suck on it?
I suspect it is also part of the problem.
you might be better off sealing the GL14 port on your condenser. three less potential leaks by my count. not to mention that vapor path makes me twitch for some reason 
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I really appreciate everyoneās help here.
Iāve spent some time upgrading my system. I reduced the hose length, exchanged the cold trap for another design so I could use a KF-25 bellow hose on the vacuum side, I moved the vacrometer to the condenserās GL-14 port, and got a new vacrometer to be sure it wasnāt that.
When blanked off, and using PTFE tubing with Teflon and hose clamps, I couldnāt get down to or maintain a sufficient vacuum (range 250 - 3000 microns). I tried it with a braided metal hose, and was able to obtain and maintain a depth of 165 microns.
After the latter result, I reassembled the system and actually made it down to 139 microns, but could not hold that depth.
Nearly every dry run has resulted in the vacuum pump achieving a āmax depthā and then the gauge readings inevitably rising again. Is this just a persistent leak, or could a serious vacuum decay take place in a dry apparatus? Iāve replaced practically everything in the setup except for the vacuum pump. Iāve changed the oil a few times, but I havenāt had it maintenanced, yet. Iām considering upgrading my pump, now.
Iāve heard the Alcatel 2021i, Welch DuoSeal, and an Edwards something-or-other mentioned on here quite a bit. Could I get recommendations on which would apply to my system the best?
Any other suggestions?
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You might be missing what exactly blanked off is. You should have almost nothing but a gauge when you do this test (no tubing etc). If you still canāt get sub 100 micron, either change your oil until you can (one change is often not enough if the pump got badly fouled) or replace the pump. Generally you should shoot for at least one decade lower than your target wet pressure. So for a goal <100 micron run, youād want to blank off at at least 10 micron. This is a crude rule of thumb because it depends on a ton of stuff, but any way you slice it if you canāt get below your target with nothing but a gauge, youāre in trouble
As far as āthe bestā, get two e2m28s and a diffstak 250, youāll hit 10^-5 torr. If spending several thousand dollars aināt your thing, take a look at the 150 other threads about SPD vacuum pumps and Iām sure there will be some good recommendations.
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What size is the boiling flask ?
Oops yust saw it s 2 liters
Your vacuum pump it self is probably the isseu
I have found very few two stage rotary vanes to be able to hit 1 micron and have a good vacuum curve if they where not made by western old school vacuum pump builders
12 cfm is good 8 beeing the bare minimum
As for pumps
Edwards
Leybold
Alcatel
Pfeiffer
Are the brands you should hope to find a decent pump 2 stage several of these brands have their pumps in singel stage with the same housing so make sure it s the right one
As for testing adding dry ice to your coldtrap might help getting lower
Adding some ptfe tape to the glass gl treads might help as well
I do not recomend pulling vacuum on the glass from more than one spot I would pull from the spider and not the head chances are your pulling uncondensed cannabinoids
And backstreaming your vacuum flow
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