Best value vacuum pumps for spd

8cfm on the 2 liter flask. Is a good avarage minimum at 12 cfm about max
Pumps with a 1x10 4 are good
Second hand pumps are often good
Take your micron gauge along When buying
Alcatel
Welch. Leybold
Edwards
Are tanks so might look soso but they often can still pull a deep vac
Don t get Chinese for service pacs
Are hard to find
Get good oil oil can make a diffrance
Use firstpass oil for firstpasses and second pass oil for seconds
Read the manual Some good underrstanding of your pump makes sense

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Guys, how can you estimate the size of the pump?.

I mean, as @Roguelab says pumps with 1x10-4 are good, but how can I compare the volume of the flask with the CFM of the pump? there is an equation, or something like that?.

For instance Labsociety says that 2L SP need an air displacement from 0.6 - 6 cfm. I dont know how precise it is, so a 20 L SP will need a pump between 6 -60 cfm?.

I appreciated if anyone can help me with that.

I have see Chinese pump with simmilar characteristics, is it real?

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As a rule if thumb 4cfm for every liter of flask
Lab sosiety are fools selling 0.6. Cfm pumps to spd folks

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Check the max vacuum of your chinees pump if it puls below 100 mic it s a start
If it pulls below 50 mic your good
If it pulls below 5 mic it s great
Main isseu is displacement under high vacuum with chinees pumps
I there for advise western pumps
Of the big brands not hvac pumps either

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Apart from pump flow and pressure, is there another important factor in choosing a pump?

parts and electrical. make sure you can get a rebuild kit.

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what pump so you have?

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It comes handy if the exaust of the pump can be atached to a hose
Terps can stink and several tricks here to handel that if you have a exaust hose atached
Info on the gaskets might be useful not all gaskets can handel solvents and terps
A good sight glass on the pump is handy to check the oil
Gives info on what is boiling off
Oil is murkey most likely water
Noise most western pumps are quite but i have worked with pumps that where not quiet anoying on a long run

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I have a 2L SPD, and i was looking for a Welch 3 8910, with 3 cfm displacement, but maybe is not enough.

Do u think this pump will work?

Go for a 8. Cfm pump they are very comon and can be found in good condition on secondhand markets
Welch wAnts you to use welch oil wich can get expensive
You can never oversize a vacuum pump i run a 2 liter with a Edwards 30 no problem even smoother run

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Island 19 general vac oil is a perfect substitute for $ welch oil.

Alcatel 2021i is an absolute perfect vac pump for 2l, 5l spd.

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Super budget option for 2L - Amazon kozyvacu 8cfm 2-stage rotary vane for under $200. Advertised at 25micron ultimate vac but it pulls down to single digit micron on my bullseye.

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Anyone clock one of these in on a bullseye? Says ultimate vacuum is 2x10-1 Pa

What you wan t to use it for ?

To close the topic and to educate everyone on the actual method of mating pumps up I will explain.

A 20cfm pump can perform better than a cheap garbo 40cfm pump. Pump quality matters. What you are looking at is the performance curve. Now another thing to remember is most pumps are supplied with a pump curve chart. Half of them are fake. The reason is becusee the Garbo pump manufacturers don’t actually know anything about testing. They throw shit parts together and don’t own a digital pump down curve analytical device. I do own one. It’s for verification and validity. The fake pump curves are obvious to anyone who understands how they work. Or claims where import pumps perform better than name brand pumps. Like when vendors claim they get lower microns than factory. It’s all a scam to sell pumps for 3x cost instead of a regular 15-25% margin. It’s all about pump profiteering. Not quality gear. (Great example a woosung Edwards 30 type Costs 800-1100 delivered to your door one at a time even white labeled, where as a Edwards wholesale is 4-5x the price - now imagine the cost when you buy 30 of these garbage pumps from over seas with near zero qc) Also the motors and rpms make a huge difference. For example there is a vendor selling re-cheapened woosung pumps they source from China that is built to a lower tolerance and cheaper build sheet - have been seen to have failing motors - where they test new at a reasonable rating but after a hour or three of use the motors burn out and or reduce Rpm and thus become inefficient. There’s alot to learn about pumps.

The method I use is the pump down rating at a giving micron rate. A quality pump that pulls say 20cfm open ballast can pull about 1.8cfm closed off at 50-100 microns(example) with a concurrent bleed allowed to establish the cusp point where the microns will not stop moving during the test.

I take the open surface area if a short path and make sure at micron rating desired I mate the pump curve at the lowest point of vacuum. The reason is because no CFM to liter rating will tell you what the pump can do and what it can handle from the boil off in the system. The only device on the market to be able to tell you this is a digital pump curve. (If you want to test your gear bring it by the shop and hook it up to my analytical pump devices for free). The only one on the market available for purchase is actually the Apollo vacuum controller that has it built in with that type of accuracy and guaranteed answer in performance. Prior to appolo nobody sold them and you’d have to pay 250k for some company to come install one in your factory, etc… Without that we only went off manufacturer ratings. This is how we manually found that many suppliers lied about the pump curve ratings.

So if I had 2.6 cuft of space in a large SPD(from fluid height to top of head, sometimes include condenser) , and my vacuum each was 1.8 CFM at desired rating, then I would pair two pumps up. Now two pumps at 1.8 CFM at desired micron rating does not equal 1.8x2. it’s more closer to 1.8x1.5-1.75 so in theory we make sure we exceed this requirement in the system with a abundance of evacuation during boil off.

This process of mating - exceeded - is actually what makes short paths run very very fast. And at lower temps. So basically you could have the best SPD out there and you’ll never hit highest speeds or lowest temps possible if you attached shitty pumps to your setup.

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Totally agree
Other thing that is underestimated
Is cold traps
You can not have to many
Those gl fitting one s are crap
But 1 trap is very little
I always recomend 2 or more

How come you haven t designed a coldtrap with a dry ice jacket yet ?
Shouldn’t t be to hard and will defenatly outperform a normal design ?

Best wishes by the way

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To distill 100ml of crude.

I have a large hk cold trap full bore.
I ran an ai full bore one after it.
I noticed zero change when running 2 vs just the oversize one i have.
Nothing ever went into the 2nd trap and if anything my vac level was a few microns lower. Not enough to matter

Well a good extracted and cleaned crude will probably not matter a lot
But did your vacuum give a stinch when running the volitiles ?
If so something is passing treu
I yust think that a good vacuum comes
From a good pump and a good coldtrap
Mechanical wise

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It’s not about what you can see it’s about what you can’t see. One trap always micro planes molecules down stream. The second usually always prevents it going past it. The deal with vacuum is evacuation and ejection from pump. The more efficient those two principles are the better it works.

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