RogueRose
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Vacuum filtration & possibly distillation without mechanical pump!
I've been trying to figure out a way to pull a vacuum on a low budget or with things on hand (or easily available). I came up with the idea of using
an old propane tank (empty) with a modified valve (replaced or modified to accept 2 way flow with a valve that can close).
A hose is needed to connect the filtrate receiver to the propane tank.
Open the valve on the tank (must allow free flowing gas in and out of valve) and place on fire - a propane turkey fryer would probably be a good
source. Heat for a few minutes until the tank is throuroughly heated. This will cause most of the air to expand as it is heated. The valve can be
closed at this point to retain the partial vacuum or it can be attached to the hose and vacuum will be pulled as the tank cools.
I think it would be beneficial to perform the filtration immediately to take advantage of the slow pressure build up (slow vacuum draw) instead of
taking the chance of the tank collapsing under too much vacuum.
Now there are risks with this. Fortunately I don't think an imploding/collapsing tank is nearly as dangerous as an exploding one -PLEASE inform me/us
if there are unstated dangers.
A few things to note - the larger the tank, the more vacuum that can be pulled and a more even vacuum will be drawn over the period of filtration.
The higher the tank is heated the more the air expands, pulling more vacuum.
Do NOT rush the cooling by trying to cool the tank with cold water as it can degrade the temper of the metal or even cause implosion. if a speeded
vacuum is required, use a fan blowing onto the tank if this is a must.
I would venture a guess that if the tank passes the pressure tests for a refill it should be capable of holding the vacuum.
The following is the percent of increase in volume of air from an ambient temp of 72F. I know humidity comes into facotr here but I don't have that
figured in yet.
It looks like to pull 1/2 bar the air needs to be heated to 600F which is an increase of 100% - or doubled in size. When cooled, that means there is
1/2 the air in the tank as what should be there at ambient temp. At 1150F it heats to 200% so you can pull 2/3 bar.
Ambient Temp 72
Deg F
120 9.03%
212 26.35%
300 42.91%
400 61.72%
500 80.54%
600 99.36%
700 118.18%
800 137.00%
900 155.81%
1150 202.93%
1200 212.27%
1350 240.50%
1500 268.72%
1650 296.95%
1800 325.18%
2000 362.82%
[Edited on 19-1-2016 by RogueRose]
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j_sum1
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The problem I see is inability to control how much vacuum is being pulled.
I think you would do better to fit a venturi device to a water tap. Check out Doug's Lab youtube channel to see how this looks.
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Detonationology
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Sounds like a cool idea... but also sounds like a bomb...
“There are no differences but differences of degree between different degrees of difference and no difference.” ― William James
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BromicAcid
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Another issue is that the seals in the valves for those sort of propane cylinders were designed to be used at standard temperatures. At elevated
temperatures, even if the valve is not heated directly, your seals/gaskets may fail and in the case of trying to maintain the vacuum this could cause
your plan to fall apart quickly. Also I do not think that your container will be able to contain enough 'vacuum' for anything other than a filtration
or so, and if you are not there to immediately stop it once your filtration starts to pull air you will quickly run through your hard work.
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Oscilllator
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Another way you could do this is to add a bit of water to the tank, so the tank ends up full of steam instead of hot air. Not only will this contract
more as the steam turns to liquid water, but the temperature should be at a maximum of 100 degrees.
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XeonTheMGPony
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A 20 pound tank will take out a small house This is a simple steam explosion if the valve where ever to fuse.
Way way too much risk and good way to kill onse self for a craptastical amount of vacuum volume.
better off using your vacuum cleaner then this!
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XeonTheMGPony
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Now after a good nights sleep head is a bit more clearer.
If all you need is a vacuum for filtering. A vacuum cleaner with a suction bleeder to allow motor cooling. Or you can fabricate a simple venturie by
using a T fiting and and a copper stub tube with a 45 degree cut end inside the T to about mide diameter, this will notproduce a monster vacuum but
should be enough for most needs.
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Dr.Bob
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If vacuum did not leak, a "stored" vacuum might work, but few systems don;t leak vacuum at a huge rate, filtrations being among the worst. So if you
don't have a consistent way to keep generating a vacuum, a filtration will stop within seconds. Just use a water aspirator or even a small wet dry
vacuum or other trivial vacuum source, but the heated propane tank is a bad idea for many reasons.
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Bert
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Cheap centrifugal sump pump from harbor freight. Water aspirator type vacuum pump. Garden hose. Garbage can or large Tupperware bin filled with ice
and water. Electrical outlet.
Hardly ever blows up the house, doesn't run up your parents water bill, or annoy them when the water pressure is always low in the shower.
If you simply MUST use an heat powered system with no electrics, learn about the history of such things- start here:
https://en.m.wikipedia.org/wiki/Newcomen_atmospheric_engine
Steam punk vacuum system...
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
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2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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RogueRose
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I'm really confused how so many people think that a smallish tank under vacuum will take out a house, let alone a room. First, the tank has to be ABLE
to fail under the vacuum created, which as I have shown, isn't going to pull 1 bar no matter how hot you heat it. I know an empty propane tank
doesn't implode at 150ft of water which is about 5 ATM or 75 PSI of outer pressure (assuming a 1 ATM inner pressure that is a 60 PSI difference).
If the tank were heated to 1200F you would have a maximum of 10PSI of vacuum pressure. I think the tank will hold. Even if it were to implode at
this pressure, very little damage would occur other than possibly falling over and rolling a bit.
I really like the idea of using a little water in the bottom to create steam, which will later condense. I have not looked into the numbers with this
so I can not comment on the numbers and saftey of this procedure.
I know there are other ways of generating vacuum but I thought the point of this forum was to explore various possibilities and support them with
relevant information, logical assesments and point out actual possible downsides - not to immediately give other alternatives (basically thread
hijacking) which have been covered ad-naseum, explain possibilities of the opposite of what is trying to be achieved (making the tank a bomb - which
EXPLODES not implodes - with exception of certain nuclear devices which use that as a trigger, not as end goal...).
The point is that this could have been a good thread, with the intelligent people who participate in this forum I am amazed that none of you know this
will work or have used it - or maybe you have and then that leads to an entirely different thread.
As for storing "vacuum" I didn't mean to keep it for weeks or months, simple minutes while doing a setup of filtration or whatever.
If any of you can prove this is a totally bad idea, I'll send you a gift card for $50 to your store of choice.
[Edited on 20-1-2016 by RogueRose]
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j_sum1
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I think you misunderstood something.
Oscilllator suggested putting a bit of water in the tank before you heat it up. Then it is not filled with air but steam. When it cools it condenses
which results in a far larger volume change than cooling air and so is able to pull vacuum for longer.
Nice idea. But Xeon exposed a flaw in it. It is possible to cause the bottle to explode while heating the steam inside it. I think you could take
steps to avoid it (ie, open the valve properly). But enough accidents have happened with repurposed gas bottles to ask questions and give everything
good consideration.
Bromic Acid also raised a very good point -- the design of the seals. They may not take heat cycles so well and even if they do, they are designed
for a positive pressure difference and not a negative one.
Myself, I think the idea fails on functionality. You are going to have quite a strong vacuum initially which will reduce over time. And all you have
to control it is an unregulated valve. The system will have a lot of inertia and will not be easy to operate. It's a novel idea, but I think there
are more practical ones.
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Dr.Bob
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The idea fails on not working. You can store compressed air practically, because a tank can hold many atmospheres of pressure, thus storing 10 or
100 atm of pressure, which is a useful amount. But a vacuum tank can only store 1 atm of vacuum, no matter how good a pump you use, so you cannot
store vacuum practically, as the container needed would be too large. A 5 gal tank cannot hold more than 5 gal of vacuum, which will drop quickly,
after 2.5 gal are gone, the vacuum will be only 1/2 an atm, which is useless. It is well established that storing vacuum is not practical for most
purposes. Just find a simple pump or aspirator, they work well, and are used by most scientists to generate a vacuum.
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XeonTheMGPony
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I do mechanical refrigeration, and I have re-used propane tanks in both Vacuum and pressure they work well.
MOP = 300psi, Vacuum as deep as you can pull.
MWP=280 psi
The Valves do have an integral pressure relief on newer ones.
When you heat steel you alter its mechanical properties called annealing
So weakened steel, fire/heat, potential fused valve in closed position can equal boom.
Water aspirated vacuum system driven by pump is best option.
MOP = Max operating pressure
MWP = Max Working Pressure
[Edited on 20-1-2016 by XeonTheMGPony]
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wg48
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I think the bottle is unlikely to fail under vacuum and if it did fail its unlikely to cause serous damage. However just like a large CRT tube
failing, occasionally a pieces of glass are expelled from the implosion that can cause serous injury.
I expect that gas bottles are manufactured from steel with some ductility so if they tend to rupture instead of fragmenting. Also many have burst
discs or over pressure relief valves.
Of cause thinking the bottle will not fail and cause serious damage is not the same as knowing it will not. If I needed too I would try it myself but
I do not recommend anyone else trying it.
The condensed steam idea will be effective in say pulling a litre of fluid through a filter if the bottle has a few or more litres capacity.
As others have said a venture type pump will do the job and even a crude one can pull up a meter of water and don't forget a fridge compressor can be
used to create a vacuum. There a long thread on that presumably explaining the limitations and problems.
Even aquarium pump that can be modified to suck and can dramaticly increase the speed of a filtration.
But note that when all the liquid has been sucked through the filter and air is pulled through it leaves the solids relatively dry compared to gravity
filtering but to do that you need a higher vacuum with a higher flow rate.
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Praxichys
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I don't think anyone mentioned a hand vacuum pump yet. It's a pain in the hand but it gets the job done.
http://www.amazon.com/American-Educational-Operated-Vacuum-w...
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immunetoN-rays
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When I was quite young and had no vacuum aspirator (didn't know what one was), I used 2 filter flasks. I put a little water in one and boiled it until
it was pretty much full of steam. The top was open . Then I took it off the heat and put a cork in the top, and as the water condensed it sucked air
through the sidearm which was connected by a tube to the other flask's sidearm. vacuum filtration! To work well, you need a LARGE filter flask for the
heated one. You're really a lot better off with an aspirator.
If you have a car I suppose you could use manifold vacuum, but then you'd need to leave your car idling as you filtered. If you try to use this for a
vacuum distillation, be sure you have plenty of gas!
For completely non-mechanical vacuum distillation there's the Charles technique: Mix zinc and acid and catch the gas in a balloon. Then use the
balloon to elevate your distillation setup to an altitude where the pressure is lower. For high vacuum work wear a pressure suit.
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NedsHead
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The MAP sensor will detect a fault and either shut the vehicle down completely (if you're lucky) or put the engine through hell trying to compensate
for the fault. it could end up costing you a lot of money replacing an engine or paying an auto electrician to restore a fault code with the computer.
I wouldn’t risk it
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immunetoN-rays
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Not that it was a serious suggestion, But I meant a REAL car. Not one of these new-fangled flibbertigibbets with their MAP sensors, and brake
boosters, and starters that active themselves when you turn the key.
I drive a pickup so old it's got 5 pedals on the floor and a manual choke to boot. I've had mechanics insist it was broken because they couldn't
figure out how to make it go.
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j_sum1
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five pedals???
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NedsHead
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I've driven tractors with 3 pedals + accelerator, but 5 pedals? it must be a nightmare to drive in city conditions.
[Edited on 29-4-2016 by NedsHead]
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tshirtdr1
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Cheap vacuum pump
Harbor freight has cheap vacuum pumps. They even have a $20 one, but I cannot attest to its effectiveness. They have some for $99 and $159 if you can
swing that.
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arkoma
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Been there, done that!
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XeonTheMGPony
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I know it really sucks eh 
Another option is a gravity vacuum pump.
Fill a very large bottle full of water, put lid on, drive the suction tube through the lid till it hits the bottom, place the drain tube in just
through the lid. Hang the bottle upside down high as you can, to start the vacuum simply open the drain valve!
Larger the bottle the longer the vacuum runs for, higher it is deeper the vacuum to a point.
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zenos2
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Agree with Dr. Bob and others.. for filtration's and such, this would die quickly. Pick up a cheap nalgene or such aspirator for ~$12+ on Amazon or
Ebay. I recently upgraded to a SS model for about $17 and have had no issues with it.
I built an adapter that connects to a water hose outlet for about $5 from hardware store parts, and even have my vac line running about 30' through a
hard plastic (HDPE?) 1/4" water supply line that holds up to anything I've inadvertently put through it, including HNO and NOx fumes, and doesn't
collapse.
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