Zombie
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Guessing this is the millionth vacuum post...
I hope this is the correct sub-forum.
I have been reading till my eyes bled, and I believe I have an inexpensive solution to building a continuous run vacuum pump for a fraction of the
cost of a new/store bought unit.
I've read all the "fridge" motor, Air Conditioning evacuates, Harbor Freight Misc. pumps, Re-purposed Compressor information I could bear.
Three things stood out as mandatory.
(1) A diaphragm pump is preferred for all the right reasons. Rubber valves are far less prone to reactions from the chemicals that many of us are
working with, there is no direct contact with the lubrication oil, ect..
(2) The pump must be capable of running for extended periods with no concern for overheating, and preferably have a low power draw.
(3) Noise is a large factor for many of us that run a lab out of the home. You have no desire to run a Model "T" ford in your lab (spare room) while
the family is trying to sleep.
There are more considerations like Max. sustainable vacuum, adjust ability of the vacuum applied, precision of this vacuum,
and a few other key points that I either don't yet know of have just overlooked for the sake of not boring anyone.
COST!!! The biggie for me... I do not want to spend 500.00 USD on a vacuum pump. I am not at that level.(yet)
I am something of a mechanical engineer (without Creds.) but I build everything I want. Have done so all my life (56yo).
I found there are readily available air pumps made for Large aquariums (300 Gal. plus) I'll post the picts...
These are diaphragm pumps, and they are meant to run for Years un interrupted. The pumps I am referring to have a flow rate of approx. 2-3cfm which
equates to a potential 29in M at their designed running rate.
The best part is they are all over the "net" at 40-50 USD.
This particular pump has a screw on air filter (intake side) that is readily adaptable to a fitting for a vacuum line.
I am proposing adapting this to hook up to a 3 gallon aluminum air tank (compressor tank) rated at 150 psi, w/ a burst rate of three times that number
or 450psi safety rating.
The pump can be enclosed in an area or box in the lab that will sound proof an already (made to be) quite pump, and using stainless wrapped vacuum
line to join the two.
These tanks sell for 30-40 USD on the "net".
From this point the working side of the tank has (2) NPT 1/4" fittings. One for a vacuum gauge, and the second foa another braided line going into an
activated Carbon filter (home made for less than 10.00 USD from PVC pipe, and (2) fittings.
The working end now goes to a simple manifold (your design) with a bleed control, and gauge. The bleed can easily (again) be hooked to an air
line/filter to keep it quite.
I have two uses for such a rig...
(1) funnel filtering (secondary Ice Trap)
(2) Purging solvents from samples overnight or longer, and again thru an Ice Trap.
I believe this is a solution I can live with, and perhaps it is something others see some long term value in.
All together it comes in at less than 150.00 USD, and should be able to last for many years.
If anyone has any input or has assembled such a rig, I would LOVE to hear it.
I would like to avoid pitfalls in my journey, and I believe I have covered all the bases (at least for my use)
On a PS... There are hundreds of Pyrex (heavy duty) domes from baking dishes ect... that are begging to be drilled, and have a bead of silicone
applied to the rim to make a proper vacuum drying chamber. These sell for about 2-3 bucks at GoodWill shops. Almost free vs. 150.00 USD PLUS for a
store bought drier.
I love this forum guys. It beats the crap out of the other "Hippie" sites, and the "I just can't understand what the hell he just said" sites.
Maybe this has been covered to death here but I have not seen it. (noob)
I appreciate your indulgence if it has been beat to death already.
Oh... I forgot to mention, a 110 volt vacuum switch can be added to regulate instead of a bleeder but for the xtra 100.00 USD... I'm happy to bleed.
 
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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Magpie
lab constructor
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Mood: Chemistry: the subtle science.
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Quote: Originally posted by Zombie  | The pumps I am referring to have a flow rate of approx. 2-3cfm which equates to a potential 29in M at their designed running rate.
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I don't understand this statement. What does "29in M" mean?
[Edited on 16-1-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Molecular Manipulations
Hazard to Others
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I think he means "Hg", which makes just about as much sense as "M" regarding flow rates.
[Edited on 17-1-2015 by Molecular Manipulations]
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macckone
Dispenser of practical lab wisdom
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My rig is an aspirator with a garden water pump and a plastic bucket. I can't get really low vacuum but it is fine down to 50mm Hg. When I need to
buffer for pH I can throw in baking soda or vinegar or both.
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Magpie
lab constructor
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Mood: Chemistry: the subtle science.
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Yes, most likely. But then how is flow rate equated to 29" Hg?
[Edited on 16-1-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Zombie
Forum Hillbilly
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Location: Florida PanHandle
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That's my mechanic way of saying inHg.
29inhg or0.9bar
I knew I should have corrected that...
I am basing this on comparable vacuum specific pumps that flow 2.5 cfm, and create 29inhg.
Here is one example... manuals.harborfreight.com/manuals/98000-98999/98076.pdf
Please excuse the oversight.
I also want to avoid aspirators. I have been down that road, and the problems they create (for me) far out weight the initial cost savings.
If I have to run any sort of pump for hours/days, I would rather take the Ron Popeil approach. You know... Set it, and something, something,
something.
The two biggest issues were humidity in the lab, and contaminated water to deal with.
Add the constant wory of something clogging and pumping water into my work... Forget abo' it!
I also distill, and run a freezer / evaporator / glycol cooling system for my condensers.
I just don't want running water inside my home.
One more edit... I also need the stronger vacuum for pulling solvents from near finished samples in a vacuum chamber. An aspirator just can't do this.
[Edited on 16-1-2015 by Zombie]
[Edited on 16-1-2015 by Zombie]
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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Magpie
lab constructor
Posts: 5939
Registered: 1-11-2003
Location: USA
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Mood: Chemistry: the subtle science.
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That aquarium air pump is designed to move air against a head that is likely no more than 5ft of water. I would not assume it is capable of 29" Hg
vacuum. I would recommend against buying it until you have the proof it will give you the vacuum you need.
You could possibly test it yourself before buying, or get a statement from the manufacturer.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Zombie
Forum Hillbilly
Posts: 1700
Registered: 13-1-2015
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That's what I am looking for, and why I posted the concept.
I follow your train of thought that I will be using this exactly the opposite of how it was designed but from my experience with mechanical pumps of
ALL sorts... I see no clear reason this will not work.
The only potential issue I foresee is a collapse of the diaphragm under vacuum.
I also have potential solutions in mind if this is indeed the case... Support the diaphragm from the outside using a stainless "fender" washer, and
increasing the stroke by adding a machined spacer to the case.
I'm kinda hoping to hear if this has been done already.
In the long run I have nothing to lose because a powerful bubble-r is always a welcome addition, and the rest of the hardware can/will be used as
intended.
Like I said, I'm here for input, and willing to toss ideas.
Who knows... This may become known as the T,A.S.A.E. pump.
[Edited on 16-1-2015 by Zombie]
They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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