Meltonium
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Vacuum Aspirator Trouble
Recently, I acquired a vacuum aspirator and a 100psi water pump to go with it. Today when I was testing it out trying to filter a solution that had
relatively large crystals for my jointed frit, it barely pulled any suction. I don't understand why there is no vacuum, please help.
P.s. I'm using nearly the same setup as NurdRage in this video: https://www.youtube.com/watch?v=tYLlkTDstmo
[Edited on 15-10-2016 by Meltonium]
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Maroboduus
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Check if your check valve is stuck. You can do this by trying to suck air through the vacuum inlet. If it doesn't flow or is very restricted that may
be the problem.
Is your hosing stiff sided vacuum hose, or is it soft and flexible? Sometimes the hose collapses from the vacuum and pinches off the flow.
What is the capacity of your pump? Aspirators need a certain flow volume and a certain pressure to work right. Just one or the other won't do it. Most
aspirators I've seen factory specs on say they need around 90 to 120 GPH at 12-15 psi.
This means the pump must be rated to flow that much at that pressure. Often when they advertise pumps they tell you the flow rate at zero pressure,
and the maximun pressure at zero flow. The company may have a flow vs pressure, or head(that's the pressure expressed in feet of water- 32 feet is
about 15 PSI) graph on their website, but some dont and you just have to get one with plenty of volume and pressure capacity and hope for the best.
See if your aspirator specifications are available on their website.
You can check if your pump is providing this by measuring the flow coming out of the aspirator while it's trying to pull vacuum, and at the same time
checking the pressure under working conditions by putting a pressure gauge in the line supplying the pump. (but it sounds like your pump is probably
making enough pressure if it's a 100 psi pump, so the flow is most likely what's lacking.)
I suppose it's possible your pump is defective, but if it's giving you the flow and pressure your aspirator needs it should still be working.
those are the most likely problems.
[Edited on 15-10-2016 by Maroboduus]
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Meltonium
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I took the check valve out, and the vacuum still wasn't present. There is some suction but not much.
My hose is reinforced and doesn't collapse. My pump operates at 4 L/min while my aspirator needs 1.5 L/min. The pump can't be defective because it got
tested right before being shipped to me. I still don't know why it's not pulling vacuum.
My aspirator: http://www.ebay.com/itm/231589093032?_trksid=p2057872.m2749....
My water pump: https://www.amazon.com/gp/product/B017NVG1I8/ref=oh_aui_deta...
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Sulaiman
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some possibilities;
1)the aspirator water inlet and outlet are reversed
2) the jet is blocked
3) the auto-off pressure switch in your pump may be pulsing,
try applying 12 Vdc directly to the motor
the aspirator dis-assembles easily,
force water just through the jet to watch how the flow is.
point the jet vertically up to estimate pressure
CAUTION : Hobby Chemist, not Professional or even Amateur
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Maroboduus
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1.5 liters/min might be the aspirator's air pumping capacity, not the water requirement.
Maybe I'm reading it wrong, but it's a little vague to me.
My Bel-Art aspirator needs 6 L/Min of water, and the Nalgene one I found on Amazon says 6.5.L/min.
I see the aspirator you bought only makes 420mm. this isn't really all that high for an aspirator, but I suspect your water flow is too low and making
it worse.
Try hooking the aspirator up to a sink or a hose and see if the suction is better. Do you have a vacuum gauge? If so take the filter out of the flask
and plug it too see what the ultimate vacuum you're generating is (with the water pump, and then try it with the sink, or hose).
Did you measure the water flow through the aspirator or are you just quoting the factory specs? Those factory flow rate numbers are usually for
maximum flow and with most pumps the flow will be much lower if there's a restriction like an aspirator on the output. That pump is to run sinks and
showers, which have less restriction than an aspirator.
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NedsHead
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it looks like it is missing 2 o rings off the main body, try unscrewing and reassembling with some PTFE tape on all the threads, and maybe try running
it off the mains water supply to determine if the water pump might be the problem
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