Time for a vacuum Guage you can make sense of, your pump should be able to reach the manufacturer specs when blanked off with a vacuum Guage attached. Start there, if the issue isn’t your pump it’s your connections somewhere down the line. I have filtration pumps that draw that hard, the Welch should be able to do better than that.
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it doesnt make sense to that 2 different welch 1400 pumps (on the same motor) give the same ‘max achievable’ on my gauge (super low) but the gauge reads perfect manufacturer specs of a 3rd smaller pump I have.
The only variable I see here is the motor. could the motor not be spinning the belt/pump fast enough? It doesnt seem to be malfunctioning
I am going to get a more appropriate gauge, but either way its gonna tell me I have a big problem…
was that “new” ebay pump actually new?
looked new to me, that would be pretty slim odds that 2 different pumps pull the exact same shitty vac. but even if the gauge is shit, i did my pass without even using it in my system and im still having to run at pretty high temps. same result.
It should pull it’s spec’ed vaccum at any speed. It’s not about cfm, just ultimate vaccum. Please test with a Guage that isn’t a mechanical dial. I don’t think it’s a fluke that your second pump preformed the same as the first.
what kind of vacuum tubing is that? I was amazed to pull like .1" less vacuum by using a silicone rubber tube instead of a gum rubber tube…
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ya thats what i was thinking on the flip side as well that if anything it would just take longer to achieve ultimate vac. but even without the gauge, i would have thought the new pump i would have seen results at lower temperatures (i used half of the same batch of crude on the old pump then the other half on the new) same temp results pretty much… could you elaborate a little more on why you think they are both giving me the same results? am i not waiting long enough for deep vac?
when i got the new pump i also got brand new vac hose as well. i believe its silicone. I wish my variable was that small 
oops vacuum always gets me cause there’s so many ways to measure it. what i meant was that try a real vacuum hose, the difference for me would bring your gauge to -0.98mpa or absolute vacuum, compared to current value, which is about 0.1mpa less vacuum.
I will be specific, the hose from Amazon below drops my vacuum level by 0.1mpa in my rotovap using an aspirator for vacuum, relative to the second usalab hose.
https://www.amazon.com/HPS-HTSVH35-BLKx10-Temperature-Silicone-Pressure/dp/B01AUST6II/ref=mp_s_a_1_5?ie=UTF8&qid=1530360940&sr=8-5&pi=AC_SX236_SY340_FMwebp_QL65&keywords=high+vacuum+tube
also as far as waiting for deep vac, with your line knotted like that, and at such a weak vacuum, I’d expect the gauge to move continuously til pretty deep vac is established… so just watch the needle, if you dont see slight movement over a 10s or less time, you’re losing vacuum somewhere. I am convinced thats your problem anyway since a new pump reads like it does for you. but super weird they would supply a terribly inadequate vacuum line with the new pump, that has me scratching my head…
Your pump won’t perform any better than its specs. If the pump is not achieving spec when blanked off something is awry. If your not getting good results when hooked up to your short path empty you have leaks. If your not getting vaccum levels that concur with the empty glassware vs the blanked off pump the lowers haven’t been fully removed. Vaccum in a distillation will start off poor, as the vapor pressure of the compound’s inside the boiling flask drop the vaccum will improve. That is why it is important to gently strip the lowers with minimal heat. Once the vaccum level improves the heat may be ramped up, and the cannibinoid fraction can be taken. A good vaccum Guage will tell you all of this data, and is well worth the investment.
Most pumps don’t come with a hose new, or at least none of mine did.
It does ‘get better’ during the process, but the ‘max’ i am ever able to achieve either blanked off or hooked up to glassware is .09 - but I agree I need a better gauge to get this data.
The gauge reads in the positive?
dude thats just blanked off to take a picture of the gauge(its inline) only hooked to the pump i have like 3 covers on one of the inlets and shoved that hose over it just for kicks
never said anything about the hose included with the pumps sale…i purchased separate from amazon, this stuff:
Great, so you found the problem.
? if you are referring to the hose, im not following. seems to be the same as you recommended. advertises Work pressure: 0.3 to 0.9 MPA - I am at 0.09
also not following you saying that -0.98MPa would be my absolute vacuum, doesnt that convert to -7350603.3 µHg 2
thanks for your replies.
Just the opposite: I can’t pull shit for vacuum with that type of hose relative to a better hose. Natural gum rubber hoses, like the white one from USAlLabequipment that I linked above, will pull a much better vacuum.
Please disregard my other comments about absolute vacuum or vacuum levels, they are incorrect, sorry doing other work and writing on my phone so made mistakes
thanks to the few who have replied. it has helped a lot just to bounce ideas off others. i appreciate it.
I got a reply from Welch today. Everyone ready?
"Yes, the base model is 1400, for example, then the suffixes designate either different intake fittings, and other variartions some time, but mostly for Motor/Electrical
1400B-01 is 115v/60hz (and is now UL I just found out!)
1400C-02 is 230v/50hz
1400W-01 is 115v/60hz, with XPRF motor
1400B-80 is for Canada customers
1402B-46 is 115v/60hz but configured for Refrigeration System Service, with handles and special inlet and Viton shaft seals
1402M-01 is 3-phase, 230v/460v, 60hz
2052B-01 is the Germany 4-head pump, plumbed to that head 1 and head 2 are stage 1, head 3 is stage 2, head 4 is stage 3. This gives fast evacuation to 56 torr and there’s a check valve right before the exhaust port since the 2-head mode would overwhelm the 1 head flow of stages 2 and 3.
2052B-01 has an NW16 flanged inlet manifold, and usually the inlet fitting 3/8” is threaded in.
For CB2052, the jar assembly has a matching NW16 flanged connection centering ring assembly, and hinged clamp.
Now, you might see 2054B-01, which is 4 heads but 2 stage, meaning head 1 and 2 and 3 are stage 1, head 4 is stage 2, meaning more flow rate (3 heads = ~95 LPM) but only 6 torr base pressure instead of 1.5 torr of 2052.
To do this, the connection pipes bewtween heads is different than with 2054.
There is even a 2057B-01 we have sold via Special Order, with 4 heads/4 stages, 38 LPM x 0.6 torr."
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