Pump for short path

thekevin07 · Mar 9, 2017

Could someone suggest a pump for a short path system. All the ones I find on google are usually part of a kit and/or cost $2000 on up.

I have a robinair 6 Cfm pump (I think it's 6) if I can use it what do I need to know I don't want to crack the glass.

Thx

gwpharms · Mar 10, 2017

You need to be able to pull vacuum down to single digit micron range.
Maybe thats a fair price for that pump but remember,
All those people selling kits your looking at typically re sell equipment to you at a signigicant mark up. For example i see summit resarch sells 1000ml round bottom flask for $100. I get pyrex ones for $40
Just shop around. Buy direct from a manufacturer. Remember your pump will be taking on solvent. No matter how many cold traps you have some can still make it through. Get a pump that can handle solvents.
Welch is one of the most poular brands now days it seems. Gast is another
I only use mechanical diaphragm pumps for quick filtration operations.
for vacuum distillation i use a reciculating aspirator pump. With one of those 2 head pumps chilled to 10c i can do about 10 micron. If i need to get lower i connect 2 pumps on the same manifold i get 4 heads and a faster flow rate and pull sub micron. My pump cost about $1800 new 800 used or you can build your own for around $300.
Good luck

thekevin07 · Mar 10, 2017

What about one like this
http://m.ebay.com/itm?itemId=361902724203

Fadedawg · Mar 10, 2017

I've been waiting for someone to post information on a cheap solution, because I'm not aware of one that reaches the lower vacuum levels.

The cheapest solution we've found so far for a 2L and under short path system, was a used Welch 1400 series. Our used 1405 cleaned up nicely and was under $2K. It is a trusty old standard, so there are also a fair number of them out there used.

Everything we operate now is larger than 2L, so Pharmer Joe has moved to Edwards, although he used a Welch Chem Star Dry with Rootes blower, on his Trommel molecular still. All way more expensive than $2K.

Fadedawg · Mar 10, 2017

thekevin07 said:
What about one like this
http://m.ebay.com/itm?itemId=361902724203

A diaphragm pump won't reach the required vacuum levels for fractional distillation.
https://welchvacuum.com/products/wob-l-pump-2522

That unit is what we use on our ovens, but not fractional distillation.

I trust that you also noted that was offered as salvage, for parts only, at that price?

Fadedawg · Mar 10, 2017

gwpharms said:
for vacuum distillation i use a reciculating aspirator pump. With one of those 2 head pumps chilled to 10c i can do about 10 micron. If i need to get lower i connect 2 pumps on the same manifold i get 4 heads and a faster flow rate and pull sub micron. My pump cost about $1800 new 800 used or you can build your own for around $300.
Good luck

Might you share the manufacturer and model number of your aspirator pump capable of those numbers?

dabbindylan · Mar 10, 2017

U need a vac that can go down to 1 torr. That can take on chems...if a aspirator exisit that can do this link it to forum...please link good chem dry vacs for under 1500

gwpharms · Mar 11, 2017

Any one if its powered and configured right
Study the veturi effect
You will probably note the specs listed for just about any 2 head recirculating aspirator pump read something like
1 pump head 20mbar @20 degrees Celsius 15 lpm flow rate. The horse power of the pump is probably listed as well.
Why would anyone pay $1800 for a pump that is barley good enough for vacuum filtrations? $150 and a trip to Harbor Freight can handle that .
Well i guess if your shopping for one the manufacturer just assumes the buyer knows how these things work and are able to make the calculations in order to determine its peak performance and figure optimal configuration to suit their needs.

What about 2 heads in parralel? In series? Whats that give you? How about 4 heads?6? How do these different configurations effect flow rate? Pump head capacity?
What does the 20 degrees have to do with anything? What would 10c do, more or less vacuum? 5c? How about 40c?
What moves faster hot or cold water? How powerful of a bilge pump do you need to move water fast enough and what temperature does the water have to be to be able to move that fast? Another peripheral device I failed to mention that would be required would be some kind of chiller recirculator so as to keep a constant consistent temperature. So to anybody interested if you don't already have one of these well that would probably more than triple the total cost. Keep in mind all that heat coming from your distillation is going into the reservoir
Sorry for answering your question with a bunch of other questions. There is a way-2 chart or graph this out it's possibly available online or you can figure it out yourself and draw your own curves and see where the dots land. Sorry I do not have time to find this for you right now

gwpharms · Mar 11, 2017

For the OP. I don't think you are going to get anything suitable for less than $1,000. Like I said maybe the one you had referenced is a fair price for a good pump I don't know. Or maybe you could find the same thing for half the price somewhere else who knows. Shop around but most importantly, bring money. You're going to need lots of it

Fadedawg · Mar 11, 2017

gwpharms said:
Any one if its powered and configured right
Study the veturi effect
You will probably note the specs listed for just about any 2 head recirculating aspirator pump read something like
1 pump head 20mbar @20 degrees Celsius 15 lpm flow rate. The horse power of the pump is probably listed as well.
Why would anyone pay $1800 for a pump that is barley good enough for vacuum filtrations? $150 and a trip to Harbor Freight can handle that .
Well i guess if your shopping for one the manufacturer just assumes the buyer knows how these things work and are able to make the calculations in order to determine its peak performance and figure optimal configuration to suit their needs.

What about 2 heads in parralel? In series? Whats that give you? How about 4 heads?6? How do these different configurations effect flow rate? Pump head capacity?
What does the 20 degrees have to do with anything? What would 10c do, more or less vacuum? 5c? How about 40c?
What moves faster hot or cold water? How powerful of a bilge pump do you need to move water fast enough and what temperature does the water have to be to be able to move that fast? Another peripheral device I failed to mention that would be required would be some kind of chiller recirculator so as to keep a constant consistent temperature. So to anybody interested if you don't already have one of these well that would probably more than triple the total cost. Keep in mind all that heat coming from your distillation is going into the reservoir
Sorry for answering your question with a bunch of other questions. There is a way-2 chart or graph this out it's possibly available online or you can figure it out yourself and draw your own curves and see where the dots land. Sorry I do not have time to find this for you right now

Might you share a link to the specific aspirator pump that you used to accomplish those vacuum levels???

Do I infer that this one is not configured right? https://www.coleparmer.com/p/water-jet-aspirator-pump/46477

Pump for short path

thekevin07

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Fadedawg

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Fadedawg

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dabbindylan

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