Sciencemadness Discussion Board

Aspirator vacuum pump

Melkor333 - 8-5-2021 at 12:37

I’ve recently got a stainless steel aspirator vacuum pump to use for vacuum distillations, and I’m using a 12V diaphragm water pump for the high pressure water needed to flow through the aspirator and generate the vacuum. The pump gives a max of 130psi (according to the manufacturer) and I use a DC power supply to power the pump. The pump works fine but I can’t seem to get a vacuum. I made sure that there wasn’t any water leaking out where it shouldn’t but I don’t know what else might be the problem. There is barely a vacuum generated.

Johnny Cappone - 8-5-2021 at 13:34

Can you post some pictures of your setup? It can help us understand what the problem is. Does your pump produce a continuous flow of water, without bubbles?

Melkor333 - 8-5-2021 at 14:13
Quote:

Can you post some pictures of your setup? It can help us understand what the problem is. Does your pump produce a continuous flow of water, without bubbles?


Yeah there are bubbles

6E1D891A-E031-4C24-9881-B65486B4B637.jpeg - 27kB659AFB59-32D2-4770-920A-9E89192285A7.jpeg - 25kB8B0E23B3-F683-4841-87A6-6EC6BCF56A8F.jpeg - 28kB

monolithic - 8-5-2021 at 16:50

Try orienting the aspirator vertically, so it's ejecting water straight down.

Panache - 8-5-2021 at 17:06

Also try praying. There’s times when I’ve fucked around with a system for hours, and gotten nowhere so I disassembled only to have it run perfectly the next day after reassembly.
Try creating a choke at the ejector output, causing a little back pressure.

Melkor333 - 8-5-2021 at 17:37

Quote: Originally posted by Panache  
Also try praying. There’s times when I’ve fucked around with a system for hours, and gotten nowhere so I disassembled only to have it run perfectly the next day after reassembly.
Try creating a choke at the ejector output, causing a little back pressure.


How would you suggest making this “choke”, cuz I’m not really familiar with this terminology?

Panache - 9-5-2021 at 21:05

Just something that slightly restricts the output flow. You can try to begin with by just very lightly putting your hand across it.

CouchHatter - 10-5-2021 at 09:32

Colder water.
Eliminate the tubing on the aspirator bottom.
Check for debris in your aspirator. Pretty obvious, but without mesh screens, anything can find its way in there. I've had to clean mine 3 times.
What brand is your aspirator?

Melkor333 - 12-5-2021 at 14:39
Quote:

Colder water. Eliminate the tubing on the aspirator bottom. Check for debris in your aspirator. Pretty obvious, but without mesh screens, anything can find its way in there. I've had to clean mine 3 times. What brand is your aspirator?


https://m.aliexpress.com/item/32969403552.html?spm=a2g0n.pro...

This is the aspirator I got

RustyShackleford - 12-5-2021 at 15:01

Melkor you are the 5th person ive seen create such a setup and get bad performance. Personally my setup creates only 0.15 bar pressure drop (0.85 absolute pressure). Very very bad, but it still works for vacuum filtering so its not complete garbage.
Ive tried changing around the tubing, but nothing works well. Its a 24V "100Psi 6L/min" chinese pump from ebay.

Screenshot 2021-05-13 005624.png - 797kB

SuperOxide - 8-6-2021 at 14:01

Quote: Originally posted by Melkor333  

Quote:

Colder water. Eliminate the tubing on the aspirator bottom. Check for debris in your aspirator. Pretty obvious, but without mesh screens, anything can find its way in there. I've had to clean mine 3 times. What brand is your aspirator?


https://m.aliexpress.com/item/32969403552.html?spm=a2g0n.pro...

This is the aspirator I got


That aspirator looks identical to the one I almost got, which is by Deschem on Amazon. I looked at this review, where a guy complained that it wasn't pulling a good vacuum, so to troubleshoot it he dismantled it and saw the vacuum port was superglued on to the main body:
Quote:
When I received it, I unscrewed all the other parts, but couldn't seem to unscrew the vacuum arm. I thought it was merely tightened on too strongly, and so I thought no more about it. In usage then, there was no hint of a valve, and water flows into the vacuum line. The vacuum suction is extremely weak to non-existent/not working, the water column into the vacuum line goes 6 to 10 inches, sometimes much more. And then that water head/height barely moves/reduces (no suction).
I finally gave up since little to no vaccum was being generated, took it off and used a pair of pliers to loosen it. It barely 'unscrewed', it more like fell out! Then I realized it had been glued on with instant/super glue... The O-ring had lost its compression and was stiff as a rock. The male threading barely has any play to screw on, and (from the pictures, you can also see) the internal threading on the main body is damaged as well... (which is why I assume they glued it back on instead).


And apparently that wasn't a one-off thing, because after that bad review, they changed the name of the product to Deschem Stainless Steel Aspirator Pump,Humboldt,Lab Vacuum Hydro Aspirators Filter Pumps Rubber O-Ring with Super Glue for Seal. I have no idea why they would do something like superglue it on instead of weld or even just solder it... But oh well.

The reason I'm bringing it up is because I can see the super glue in the photo of the aspirator product in the link you shared:
Stainless-Steel-Aspirator-Pump-Humboldt-Lab-Vacuum-Hydro-Aspirators-Filter-Pumps.jpg_Q90.jpg - 67kB

Also, I was talking to another user about aspirator pumps (over PM), and when I showed him that review, he said he had that identical pump a while ago, and now realizes that it was also glued together (but didn't realize it at the time):
Quote:
Not gonna lie, that super glue stuff IS pretty sketchy of them. But at least they decided to disclose as opposed to turning the other cheek and attempting to gaslight customers, I guess. The one I had did have threads there, though. I distinctly remember what I now realize was the glue failing after which the port could be rotated. Also, when it broke off, the male port clearly had the female thread embedded in it. There was an o-ring too, but it seemed almost as if the joint wasn't designed to be sealed with one. Tightening the port pretty much squeezed the o-ring out. It seems to me that they sought to strengthen the joint and fix the o-ring in place by applying glue.


If yours is glued on (which you should be able to tell), then perhaps the glue failed and it's pulling in air from the broken seal, which you can either fix or return. Super glue is bound to fail when small amounts of solvent vapours get pulled through the vacuum port.

I plan on ordering the identical pump you have and set it up with my aspirator (which is this one here, works like a charm on my kitchen tap), and then maybe add a PWM speed controller for the DC motor inside the pump (with the reverse diode fix that they don't usually come with, so the motor/PWM doesn't get fried).

[Edited on 8-6-2021 by SuperOxide]