Sciencemadness Discussion Board - Decent vacuum pump

Decent vacuum pump

Mateo_swe - 10-2-2021 at 00:14

So i have some small diaphragm pumps that i use for filtrations and an aspirator.
But i have wanted a good diaphragm vacuum pump that can be used to for example fractional distill aromatic oils and other stuff.
I have looked at the new chineese pumps but when browsing around ebay i made an impulse buy of a used Vacuubrand MZ-2C diaphragm vacuum pump.
I have checked and one can get replacement diaphragm membranes and valves for it.

Is this a good vacuum pump?
The seller said it is in excellent working condition and have been tested to pull vacuum of 12 mbar (9 torr or 9 mm/Hg).
Is this a decent vacuum that can be used for fractionally vacuum distill stuff?

Here are some pictures from the seller, the pump is beeing delivered now.

River21 - 12-2-2021 at 18:49

I am not only also curious about the same... but also I have to replace the "gasket" for the two big halves of the Edwards e2m1.5 I have... what material can I use... I don't think I need the super expensive name brand I could cut one myself

dawt - 12-2-2021 at 23:30

That's an excellent pump and should last you a long time! It should easily reach 10-15 mbar, which is fine for most components of essential oils, but might not be for the highest boiling ones. Which oils are you planning on fractionating?

I am curious as to where you found replacement parts, though. Last time I looked I didn't find a place that sold to individuals... Or the parts were almost as expensive as a new used pump. Don't remember.

Fyndium - 13-2-2021 at 00:51

Diaphragm pump is likely more resistant against chemicals than rotary vane oil pump. I've been using them, though, because they're 60€ with shipping from ebay and readily reach 10-15mbar vacuum so that 180C boils at 45-50C. Practically it will be convenient to change the oil frequently, or replace the entire unit if it corrupts sufficiently.

Only major downside of these pumps is that they heat A LOT in rather short timeframe, and running them any longer than 15-30 minutes requires heavy external cooling, and with heavy I mean 600m3/h duct fan blowing directly onto them. I decided to simply make a circuit of my duct fan so that it sucks air from fume hood(for odor control, mainly), it passes through a duct into a carton box where I've placed the pump, and then it goes into the fan and activated carbon filter. This creates high airflow that removes any odors from the hood and from the pump and keeps the pump reasonably cool.

Mateo_swe - 13-2-2021 at 04:06

Thanks for the info.
So it´s a pretty good vacuum pump if its in good condition

Regarding the replacement parts i found them listed at the pump producers webpage, here:
https://www.vacuubrand.com/en/page1033.html

It doesnt say what the cost is for these spare parts and they might be expensive.
Maybe something can be fabricated if one can get the right material for the diaphragm.
If the pump gets very hot i can make some fan cooling, i have some different fans that could be used.

Which oils are you planning on fractionating?
Well for a start i might steam distill some aromatic oil from plants we have in the garden, then fractionally distill the oil but i have no ideas yet.
I would like to learn and get some experience with vacuum, something that smells nice would be fun to fractionally distill and try to isolate the aromatic compound.
It will be nice to be able to vacuum distill anything really, im sure i will use it in the future.

MZ 2C Replacement diaphragms and valves.jpg - 31kB

[Edited on 2021-2-13 by Mateo_swe]

Fyndium - 20-3-2021 at 06:36

https://www.ebay.com/itm/KNF-Neuberger-Laboport-UN840-3-FTP-...

Is this a good priced vacuum pump, and a good pump itself? I'm sort of tired playing with oil rotary vane pumps, they overheat without using 1000m3/h duct fan with exhaust box and they lose power by that, and when the oil contaminates with all stuff that will carry over every single trap and precaution one takes.

Can those ultimate vacuums be adjusted with these pumps, or does one have to use simple bleeder valve to control it separately? 8mbar is an excellent vacuum, the same my new rotary vane reached when it was new and ice cold.

monolithic - 20-3-2021 at 09:06

Quote: Originally posted by Fyndium

https://www.ebay.com/itm/KNF-Neuberger-Laboport-UN840-3-FTP-...

Is this a good priced vacuum pump, and a good pump itself? I'm sort of tired playing with oil rotary vane pumps, they overheat without using 1000m3/h duct fan with exhaust box and they lose power by that, and when the oil contaminates with all stuff that will carry over every single trap and precaution one takes.

Can those ultimate vacuums be adjusted with these pumps, or does one have to use simple bleeder valve to control it separately? 8mbar is an excellent vacuum, the same my new rotary vane reached when it was new and ice cold.

Seems really expensive. I have one of these. https://www.ebay.com/itm/KNF-Neuberger-UN726-1-2-FTP-115VAC-... I've run it for several hours with no signs of overheating. It should pull down to 10 torr. I've measured mine to 12 torr with an uncalibrated pressure transducer. The one of the auction is configured for parallel pumping (high volume) rather than serial pumping (high vacuum.) I believe you can switch it yourself, the manual shows how to do this: https://atecorp.com/atecorp/media/pdfs/data-sheets/KNF-UN726...

Fyndium - 20-3-2021 at 09:25

Hmm, strange - why does your manual state that your pump is only designed to reach 50torr (67mbar) vacuum?

Any idea what these pumps cost new? And how noisy are they?

Since the rotary vane oil pumps cost about 60$ a piece, I'd rather buy 10 of them and replace them as they wear, than invest into a machine that does not deliver very high and consistent level of vacuum without major maintenance.

monolithic - 21-3-2021 at 17:52

Quote: Originally posted by Fyndium

Hmm, strange - why does your manual state that your pump is only designed to reach 50torr (67mbar) vacuum?

Any idea what these pumps cost new? And how noisy are they?

Since the rotary vane oil pumps cost about 60$ a piece, I'd rather buy 10 of them and replace them as they wear, than invest into a machine that does not deliver very high and consistent level of vacuum without major maintenance.

That's single stage / parallel configuration for less vacuum but higher volumetric flow rate. Dual stage / serial configuration pumps to higher vacuum but lower volumetric flow rate. I've torn my pump apart and I believe the only difference between the two configurations is the routing of the hoses, as shown in the manual.

New? Probably $1000-2000. Lab grade diaphragm pumps, especially PTFE models, are very expensive. Even used they're largely a ripoff. I waited for a quite a while and bought mine for $150 (KNF UN726.3.) Chinese rotary vane pumps are definitely more cost effective, even if they are kind of shitty.

[Edited on 3-22-2021 by monolithic]

Fyndium - 22-3-2021 at 00:57

So what you are saying that is by simply changing the hoses to series instead of parallel you will get full vacuum performance on the cheapest one with two diaphragms as well?

zed - 22-3-2021 at 02:18

Ummm. Some pumps used to be plumbed to be set up in series, if required. I haven't worked with anything like that for a while. Just cheap stuff. Works OK, but it ain't classy. Well, it isn't classy, and it can't pull a really hard vacuum either.

Ten Torr is a very good vacuum for most purposes. It might not be a hard enough vacuum for really high-boilers, but it's generally a pretty good vacuum.

New stuff for me. First time I saw someone using a diaphragm pump, it was being used to vacuum distill Nitric Acid.... The premise being, that the diaphragm pump, would be un-effected by the noxious gases.

Back in ancient times, we used to utilize an aspirator pump for such things. Usually dissolves the bad stuff in water, doesn't always require electricity, so it's explosion proof, and you can set up the pump, on a faucet out in the middle of your back-yard, which happens to be a nice place to send hydrogen to.

Still, it's awkward. And, an aspirator absolutely, positively, will not pull 9 Torr. Possibly 20 or 30, maybe.
And, you always have to be on guard against "suck-back".

It's possible, I'll see a fancy pump at an auction, and no-one will recognize it for what it is. In which case, I'll buy it.

Nitric the nice way! UC235 nitric acid. That fancy pump is worth having.

https://www.youtube.com/watch?v=DEEjNQN2dIQ

[Edited on 22-3-2021 by zed]

[Edited on 22-3-2021 by zed]

[Edited on 22-3-2021 by zed]

monolithic - 22-3-2021 at 04:02

Quote: Originally posted by Fyndium

So what you are saying that is by simply changing the hoses to series instead of parallel you will get full vacuum performance on the cheapest one with two diaphragms as well?

Yes, I believe so. The parts list doesn't indicate any differences between the two configurations (other than the hoses that span the two heads) and I've torn my 10 torr model apart for maintenance -- there's nothing inside the head to indicate any special part that enables 10 torr. If you switch the hoses around as show in in the manual, I believe it should pump to 10 torr just fine.

[Edited on 3-22-2021 by monolithic]

Fyndium - 22-3-2021 at 04:45

Then I'll be keeping an eye on eBay for it. Thanks for the advice.

Mateo_swe - 25-3-2021 at 04:07

I have noticed that if you keep check online auction sites often for used vacuum pumps of good brands sometimes good deals do turn up.
I did buy my vacuum pump in the top of the thread as a impulse buy and i really had no clue if i payed a good or bad price.
But it seems the brand and model i bought often goes for around 500-800Euros so im really happy as i paid little over 200Euros and it seems to be in good condition and works good.
So good deals can be found if not in a hurry.
Someone said that replacement diaphragms and valves can be expensive so availability and cost of those can be worth check out before making a expensive purchase of a pump.

OrganicGuy - 7-4-2021 at 00:58

Quote: Originally posted by Fyndium

Diaphragm pump is likely more resistant against chemicals than rotary vane oil pump. I've been using them, though, because they're 60€ with shipping from ebay and readily reach 10-15mbar vacuum so that 180C boils at 45-50C. Practically it will be convenient to change the oil frequently, or replace the entire unit if it corrupts sufficiently.

Only major downside of these pumps is that they heat A LOT in rather short timeframe, and running them any longer than 15-30 minutes requires heavy external cooling, and with heavy I mean 600m3/h duct fan blowing directly onto them. I decided to simply make a circuit of my duct fan so that it sucks air from fume hood(for odor control, mainly), it passes through a duct into a carton box where I've placed the pump, and then it goes into the fan and activated carbon filter. This creates high airflow that removes any odors from the hood and from the pump and keeps the pump reasonably cool.

That a very good price, a diaphragm 10mbar for 60 euro. Could you please send me a link to that one, if it's still around for sale. Any other suggestions I would appreciate very much. I need a fairly good diaphragm pump (at least 22 torr, preferably little more, price up to 100 euro is OK)