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Author: Subject: Looking for info on vacuum pump to buy, compiled short list of products Im interested in. Advice/Critiques/Suggestions...
Rocket89
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[*] posted on 18-1-2016 at 09:32
Looking for info on vacuum pump to buy, compiled short list of products Im interested in. Advice/Critiques/Suggestions welcome!


Hello, I'm a long time lurker, first time poster. First off I want to say thank you to everyone on here, I have learned a lot from just reading this board.

Over the last year I have started putting together a little garage lab with your standard distillation and filtration glassware, stands, clamps, etc. I'm at that point where I want to buy a decent vacuum pump. Mostly for vacuum filtration and desiccation purposes, but also for the occasional vacuum distillations, and sporadic automotive applications.

Now, I did UTFSE, but not extensively, and I might've missed something, I didn't find much information regarding suitable pumps for the garage chemist.

Here are the links to the pumps I have found and taken an interest in. This is by no means conclusive and if anyone has any other options (particularly cheaper), then I am all ears.

Cole-Palmer Vacuum/pressure diaphragm pumps, PTFE-coated wetted parts, 0.75 com, 115 VAC
Link: http://amzn.com/B003LYSFS6

Two Stage 12.0 CFM, 1 HP, Deep Vacuum Pump
by Western Pacific Machinery
Link: http://amzn.com/B00TRAB6NO

HFS Vacuum Pump Single Stage 110v - Inlet: SAE 1/4"-3/8"; 22.5micron, 1hp , 12cfm 3pa
Link: http://amzn.com/B00VF1EUYK

HFS (Tm) 12 CFM Vacuum Pump Double Stage 110v - Inlet 1/4 and 3/8 Inch SAE- 1 Hp - 340l/min
HardwarefactoryStore.com
Link: http://amzn.com/B00XFLA2MC

Diaphragm Vacuum Pump Oil Free Type 15L/m 75W 0.075Mpa 250mbar 110v OR 220v
by MX
Link: http://amzn.com/B00WB3ZZ5Y

I am leaning towards the Cole-Palmer as it is PTFE-coated, and with my limited understanding, would last the longest when filtering organic solvents, corrosives, etc. But then again, it is fairly expensive, and though affordability isn't exactly a sticking point, I am not opposed to spending less for a "comparable" product. Especially since I will be have a bubbler/trap set up anyway.

Any and all advice, suggestions, etc, will be greatly appreciated! Thanks, Rocket.

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Heavy Walter
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[*] posted on 18-1-2016 at 09:58


Hi Rocket89

Me too an old lurker and a new member.
I have a small high vacuum lab and planning some chemical synthesis.
Think of having two vacuum systems: a simple water jet for filtering and low requirements, easy (in case you have running water close to) and an elaborated system (two-stage rotary pump plus diffusion pump -air or water cooled) with high-vacuum reading.
The high vacuum system will be helpful for delicate syntheses.
Don't need to buy new ones: e-bay offers are interesting and cheap.
Water jets come in glass, plastic or metal, no too expensive.
High vacuum is tricky: leaks are common and pinpointing them not so easy. You will have to do your own practice.
Feel free to ask me any doubts.
Can send you some images.
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Heavy Walter
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[*] posted on 18-1-2016 at 10:18


See my synthesis line.
It is partially disassembled: diffusion cooling fan was removed and high vacuum gauge is missing.
The black instrument is for pressure readings of gas stored at the upper flask.

Linea de Sintesis_01.jpg - 156kB
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Dr.Bob
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[*] posted on 18-1-2016 at 10:45


The Cole parmer pump has a loq CFM (0.75) and a poor ultimate vacuum (Max vacuum: 23.2" Hg). The Western Pacific Machinery one is much higher flow (12 CFM) and a better ultimate vacuum, but is an oil pump. The others are also fine for some tasks, depends on what you want to do.

If you just want to filter stuff and do minimal vacuum work, then the Cole Parmer might work, but if you want to really have a high vacuum (boiling high BP compounds, drying materials under vacuum), then the second one is much better, but you should put a trap of some sort between the pump and the work to protect the pump, or even an acid filter (container of K2CO3 or the like to absorb acid vapors). Diaphragm pumps can rarely get a high vacuum or high throughput, but they are more resistant to chemicals. But you have to buy a bigger diaphragm pump if you get one of them, in order to do much with it, to match the suction of an oil pump, or even a direct drive rotary pump. Also, check the duty cycle, and make sure the pump can be left on continuously, if it only shows an hour or so, the pump will not go long before dying in real usage.
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Sulaiman
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[*] posted on 18-1-2016 at 14:03


For vacuum filtering I have found this http://www.ebay.co.uk/itm/DC12V-DC-Micro-Piston-Vacuum-Pump-...
small pump more than adequate.

I bought a 2-stage rotary vane vacuum pump, 0.3 pa ultimate pressure
a single stage, 5 pa would be just as useful for distillations etc.

With cheap Chinese rotary vane vacuum pumps costing less than the refurbishment cost of a 'proper' vacuum pump
I can not see the value of an expensive rotary vane oil sealed vacuum pump,
unless you have other uses for it.
e.g. http://www.ebay.co.uk/itm/3-CFM-1-4HP-Single-Stage-Rotary-Va...

maybe a chemically resistant diaphragm pump is overall best for chemistry?
( I want one ! )
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elementcollector1
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[*] posted on 18-1-2016 at 15:52


Personally, I prefer https://www.amazon.com/gp/product/B012CFTYX4/ref=oh_aui_deta... for both price and efficacy.



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[*] posted on 18-1-2016 at 16:33


I personally own this pump, which I bought used on eBay for $60. Typically I see them around $100. The only issue I've had with it so far is that the diaphragm teared, and a replacement cost $66! Wasn't terribly happy about that, but it's the cost of a diaphragm pump(on the upside, it's oil-free). The pump is more than sufficient for vacuum filtrations and many vac distillations, but it only pulls around a 175 torr vacuum which doesn't lower the boiling point as far as I would like/potentially need it to for certain compounds.

I would recommend a KNF pump if you want a good diaphragm pump. They pull around a 20 torr vacuum and, like the pump I have and the Cole Parmer you linked, they have a Teflon or Viton coated head, a feature which I consider to be essential for use in organic chemistry(traps are a pain). The downside is the price, around $300 for a used pump. I couldn't justify this when I was buying one, but if you can fit that into your budget, then I would definitely go for one of those.

UN726FTP-Single-Head-Diaphragm-Vacuum-Pump.JPG - 21kB

[Edited on 1-19-2016 by gdflp]




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XeonTheMGPony
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[*] posted on 18-1-2016 at 16:51


Too powerful of a vacuum pump is a bad thing with out implementing a gas ballast (Way to admit air in between the stages) a 2 to 3 CFM dual stage is plenty for most jobs, secondly I'd suggest you build a cold trap for it as well (Will vastly increase the life of the pump and pump oil!)

DO NOT WASTE TIME WITH SINGLE STAGE UNITS! If you plan to do any serious vacuum stuff they are an utter waste of time, money, effort! All so avoid cheap name brands they will not last! Sadly you need to be care full with even Yellow jacket gear now days. Use a quality 3M or Nu-Calgon oil (http://www.nucalgon.com/products/oils/vacuum-pump-oil)

As said above have a smaller pump for the filtration and distillations then the higher powered one for dessication.

A Supco Vg46 (http://www.amazon.com/Supco-VG64-Digital-Accuracy-Connection...) vacuum gauge is a very nice mid range vac gauge that measures in Torr and MiliTorr, Microns, Inches of mercury.

I had mine tested at a laser fabrication factory and it will measure down to 1.0Militorr! (Awesome having such a place next door to me, just wish they'd sell me glass stock)

BTY you can make an ok cold trap using an old water cooler with some modifications!

For high vac system use all 1/2 Copper soft annealed, then terminate to your final size at the final point of utilization for best performance.

[Edited on 19-1-2016 by XeonTheMGPony]
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[*] posted on 18-1-2016 at 21:26
Vacuum pumps on Elemental Scientific


I have some used Schuco vacuum pumps that my customers like. Nice pumps for a reasonable price. Here's the link Schuco Pumps.

Tom




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kt5000
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[*] posted on 18-1-2016 at 21:49


Quote: Originally posted by tomholm  
I have some used Schuco vacuum pumps that my customers like. Nice pumps for a reasonable price. Here's the link Schuco Pumps.

Tom


Funny, I was getting ready to post a link to the Schuco 130A on your site.. I've started looking for a vacuum pump as well and figured the pump+trap design was handy. I've only used house vacuum in college lab, so I'm still figuring out what would be good for home. I'm planning to do some vacuum distillation and filtering. Nothing too fancy.

Schuco 130A: http://www.elementalscientific.net/store/scripts/prodView.as...
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Rocket89
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[*] posted on 20-1-2016 at 22:48


Thank you everyone for all the input. Looks like I will be going with a 2 stage rotary pump.


Rocket

[Edited on 21-1-2016 by Rocket89]
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XeonTheMGPony
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[*] posted on 21-1-2016 at 06:06


Good choice, now learn about vapor pressures and their effects on substances, sublimation, triple points, and cold traps (Cold traps will be the most critical part on vacuum desiccation! (Well pretty much every thing).

The oil is the life blood of your vac pump! Keeping it clean and dry is critical.

Trick is warm up the pump first befor using it for the function (Helps keep the oil dry) When the oil is saturated it will look milky or foggy.

Change the oil early and often (Oil will be cheaper then the pump!) If doing acid distillation you will need very aggressive scrubber drying system leading to the pump.
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[*] posted on 21-1-2016 at 10:52


I bought a Harbor Freight one-stage vacuum pump that uses oil. It will pull down to 1mm Hg. Tell me why I would need a 2-stage.



The single most important condition for a successful synthesis is good mixing - Nicodem
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XeonTheMGPony
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[*] posted on 21-1-2016 at 16:21


Quote: Originally posted by Magpie  
I bought a Harbor Freight one-stage vacuum pump that uses oil. It will pull down to 1mm Hg. Tell me why I would need a 2-stage.


It will not pull that for long (Providing it can actually even get near that in real world usage) if you actually use it for any amount of time, all so it will take much longer to get even close to that rating!

When dealing with larger volumes the first stage is the rapid pull down, then once it gets down to a usable vacuum the second stage kicks in to get you to the final vacuum rating. At this point the first stage is still working!!! It is helping the 2nd stage pull a deeper vac by keeping the middle pressure zone at a much lower presser then atmospheric, this is why a single stage will never pull to a deep vac no matter their claims!

Real world usage only a two stage will get near its rated ultimate vacuum even after multiple usages! But keep in mind this is providing one gets a quality pump to begin with! Cheaper ones go down even worse, the 2 stage ones hold out a bit longer but cheap is cheap.

[Edited on 22-1-2016 by XeonTheMGPony]
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[*] posted on 21-1-2016 at 16:37


My question is based on "real world experience," ie, my own, on several occasions. I usually set up my vacuum distillations with 19/22 tapered glass, well greased joints with silicone vacuum grease. I think my pump is rated at 2.5cfm. I measure my vacuum with a Bennert mercury gage. This vacuum of 1mmHg is reached very quickly.

So far I have not abused my pump, ie, I've only used it on fatty oils and alcohols, etc, and have not had to use a trap. I've changed the oil once, I can't remember why, probably because I estimated it might contain enough fatty oil contamination to no longer remain a good lubricant.

[Edited on 22-1-2016 by Magpie]

[Edited on 22-1-2016 by Magpie]

[Edited on 22-1-2016 by Magpie]

[Edited on 22-1-2016 by Magpie]




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XeonTheMGPony
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[*] posted on 21-1-2016 at 16:47


On such a tiny system you may get away with it, but as time and age effect it they do not hold up. (We are talking about industrial type pumps right? as these are no where in the same league of a scientific built single stage unit!)

Admittedly I am coming from the perspective of my vac pump is a critical tool and used on refrigeration systems that contain huge volumes of gas by comparison, but seeing single stages side by side 2 stage units the single stages are not worth even looking at.

BTY try it on a digital vacuum gauge! My pump will get to 25microns (same as milliTorr) Ultimate vac (Analog gauges are useless to reading this level accurately)

All so oil should be changed after so many run hours regardless of how it looks!, oil is cheap, a good quality of vacuum pump is not!
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Magpie
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[*] posted on 21-1-2016 at 16:58


Quote: Originally posted by XeonTheMGPony  

Admittedly I am coming from the perspective of my vac pump is a critical tool and used on refrigeration systems that contain huge volumes of gas by comparison, but seeing single stages side by side 2 stage units the single stages are not worth even looking at.

BTY try it on a digital vacuum gauge! My pump will get to 25microns (same as milliTorr) Ultimate vac (Analog gauges are useless to reading this level accurately)



I am speaking from the standpoint of the home chemist which I assume includes the OP and most of the others here that are interested in buying a vacuum pump.

Have you done any home chemist vacuum distillations? I would think that 99% of them don't care about discrimination in the sub-torr range.




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[*] posted on 21-1-2016 at 17:40


but he did specify vacuum desiccation, for that you want the best ultimate vac! So yes I did think of it, that is why I recommended against getting a 12cfm one! a 1.5 to 3 is tons.
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[*] posted on 21-1-2016 at 18:48


I think the amount of vacuum required for dessication would be application specific and would usually not be < 1mmHg. For example, this vacuum dessicator specifies a vacuum of 27"Hg - not much of a vacuum:

https://www.ece.umd.edu/MEMS/resources/sop/vacuum_dessicator...

For vacuum distillations at the home lab scale not much capacity is required either. If the system holds a vacuum it will suck down very fast with a 2.5cfm unit. If it doesn't hold a vacuum the system seal should be corrected.





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[*] posted on 21-1-2016 at 21:13


I am in total agreement with Magpie on what is a sufficient vac pump for the home lab. I do many vac distillations with a "cheap" single stage pump using standard ground glass joint glassware. I use a digital gauge (which cost far more than the pump) and my pump will routinely pull 0.5mm or better on properly greased joints. Frequently, I have to have a bleed to raise the pressure. I NEVER use the pump for filtration or bulk solvent removal. For that I have a recirculating aspirator pump which pulls in the 20-25 mm range. It saves much on water usage - very important here in California. I got one a couple of years ago on Ebay for about $200- expensive but worth every cent. I really recommend such a unit if it is within your budget.

In my working days, we did a lot of freeze drying of aqueous samples using vacuum at 2- 3 mm, sometimes worse. At the end of the day, it all comes down to application and what is sufficient.

AvB
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[*] posted on 22-1-2016 at 03:39


A 'Cold Trap' may be trivial in a full laboratory but I have found it not practical at home
a small water-ice&salt etc trap does not cool common solvents or even water enough
and because here in UK dry ice is GBP 35 for a minimum order of 10 kg
which is more than the cost of the 3 cfm 5 pa rotary vane pump pointed to by elementcollector1 :o
These cheap rotary vacuum pumps are sold as devices to suck all of the water out of automotive air-conditioners,
so they should be fairly tolerant of a little water or solvent vapour.
I have not used mine enough yet to give any comments on long term reliability though.

If you do buy an expensive rotary vane vacuum pump, consider the cost of looking after it,
especially dry-ice cost and availability.



For filtration a continuous vacuum pump is not required as the filter flask 'holds' a lot of vacuum
so even a hand vacuum pump will work fine.
My little 12 Vdc, -80 kpa (150 mm Hg absolute ... on a good day) vacuum pump can pull filtrate of plant extracts through a 90 mm diameter 'slow' paper quickly.

A continuous pump would allow rapid air-drying of the Residue

[Edited on 22-1-2016 by Sulaiman]
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[*] posted on 22-1-2016 at 10:27


The dry ice situation is pretty good in the US apparently. Although I have not bought any for some time websites are claiming it can be had for $0.99/lb. This then would be a minor cost of most of my experiments.

Edit: I see there are minimum purchase amounts however. I'm not sure what these are yet.

Dry ice should be dirt cheap. I believe it is a by-product of the industries who extract O2 and N2 from the air. I see it in small (locked) freezers at Walmart for consumer use. In liquified form it is being delivered in tank trucks to restaurants and taverns for carbonation of beverages.

[Edited on 22-1-2016 by Magpie]




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[*] posted on 22-1-2016 at 14:58


You do not need dry ice for most low vacuum set ups, a modified water cooler will do the job.

Unless you plan to separate out alcohol at 300 microns(MilliTorr) then you'd want -80c! Cascade system! (Easy to build it is the gasses that will kill your budget though!)

I have one similar to this: http://www.ebay.com/itm/Vacuum-Pump-2-6-CFM-R12-R22-R134a-41... (Mine is 1.5cfm)

That I use for most my vacuum distillations using ethanol based solvents with recovery of the ethanol. I do them under a deep enough vac I can boil the ethanol at room temp! To control vac I use a needle valve to bleed in air between the pump and apparatus for the distillation.

As I rebuild the system I'll be sure to put up pictures.

[Edited on 22-1-2016 by XeonTheMGPony]
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[*] posted on 22-1-2016 at 16:44


Quote: Originally posted by XeonTheMGPony  
... a modified water cooler will do the job.


Please explain.




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[*] posted on 22-1-2016 at 17:00


removing the thermistat and lock it on or off, baffel the cold pot and pack with copper scrubbies, insulate the out side.

they will get down to apx -17 when left to run long enough.

Once down to lowest temp set your vac limmit to match. Not the prettiest but works.
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