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darryl
12-05-2010, 06:32 PM
That's it- nothing else to describe. I'm thinking of re-purposing an aluminum fire extinguisher can to hold white glue. I would like to use pressure to force the glue through a nozzle, with a regulator knob and needle valve. Shop air is at 90 psi here- the can has been tested at 300 psi according to the literature on it. I'm not concerned about the nozzle design, et al, just the possibility of the pva eating the can, or the can altering the pva. I've looked but I can't find a compatabilty rating for pva with al.

If I recall, white glue will darken the aluminum surface, but I don't know if an adverse chemical reaction takes place in the glue or the metal.

squirrel
12-05-2010, 07:35 PM
That's it- nothing else to describe. I'm thinking of re-purposing an aluminum fire extinguisher can to hold white glue. I would like to use pressure to force the glue through a nozzle, with a regulator knob and needle valve. Shop air is at 90 psi here- the can has been tested at 300 psi according to the literature on it. I'm not concerned about the nozzle design, et al, just the possibility of the pva eating the can, or the can altering the pva. I've looked but I can't find a compatabilty rating for pva with al.

If I recall, white glue will darken the aluminum surface, but I don't know if an adverse chemical reaction takes place in the glue or the metal.
It can't be too bad, I am still alive. Many years ago in grade school we would eat paste and glue.

fredf
12-05-2010, 11:15 PM
That's it- nothing else to describe. I'm thinking of re-purposing an aluminum fire extinguisher can to hold white glue. I would like to use pressure to force the glue through a nozzle, with a regulator knob and needle valve. Shop air is at 90 psi here- the can has been tested at 300 psi according to the literature on it. I'm not concerned about the nozzle design, et al, just the possibility of the pva eating the can, or the can altering the pva. I've looked but I can't find a compatabilty rating for pva with al.

If I recall, white glue will darken the aluminum surface, but I don't know if an adverse chemical reaction takes place in the glue or the metal.


is the fill opening large enough to slip a plastic bag in the cylinder?? glue in bag and pressure out side perhaps a hose clamp the bag on a barb??

BillDaCatt
12-05-2010, 11:45 PM
The primary corrosive element in PVA glue is water. I do not recommend sustained contact with water inside an aluminum pressure vessel. It will be difficult, maybe impossible, to tell if such contact will compromise the container over time.

I'm not saying it won't work. I'm not even saying that it won't work for a long time. I'm only saying I would not do it.

I think doing this is potentially very dangerous! You did not say how big this container is, but the larger the container is - the bigger the danger is if it fails. :eek:

darryl
12-06-2010, 12:03 AM
Perhaps I could insert a liner, though I think it would be a PIA overall. I'm wanting to use an old fire extinguisher bottle, already threaded and wide enough to stand up without falling over. My main concern is that the glue doesn't somehow start to gel because of the contact with the bare aluminum. I suppose I could coat the inside with something- maybe I needn't bother though. I'll try again to find some info that might be relevant, other than that I might just go ahead and use it as is.

I'm kind of tired of using the ol' glue bottle, tipping it over, waiting for the glue to run to the tip, dribbling out if you lay it on its side, uneven speed of glue coming out, etc. I want a self-cleaning nozzle, adjustable, with trigger, and no waiting for glue to be ready to squirt. Pull trigger, glue comes out evenly- break off excess from outside of tip from time to time. Pick it up, glue is always ready to come out-

I'd momentarily connect the air hose, then remove it. The pressurized can would have a diminishing pressure as glue is used, but that should be easily adjusted on the go plus I do have a design in mind to compensate for that. I think it would be a time saver overall- just push a button to release the pressure, unscrew the cap, fill 2/3 with glue, put the cap back on, pressurize the can- you're ready to squirt glue. You can either refill the can before it's empty, or repressurize once during the use, then refill when the glue runs out. I like the idea of being able to pull a trigger and release right away- gets you a more or less measured amount of glue where you want it, and the tip stops running right away. Then if you want a continuous bead of a fixed size, you just hold the trigger and move as fast as it takes to lay the right bead down.

When leaving it for a time, coffee break or whatever, just push the release button and the pressure drops to zero. No long-term bleedout of glue. My design so far has the exit nozzle at a 45 degree downward angle- tilting the can would get the tip lower than the bottom of the can. This would allow laying a bead of glue on anything flat on the bench, which is what most of my work is. Some days I'll go through three or four fills of my existing glue bottle, and during that time the bottle is starting to fall over when it gets low, and I'm constantly dealing with a varying size of bead-

Ok, I know there are cabinet makers out there who wouldn't have seen this to be a problem, but I can't resist trying to make the situation better. One other idea I've had is to have the 'bottle' in a fixed position, then a hose leading off to a nozzle with a trigger. That might work, but I'd love to have this thing totally portable and 'cordless'.

J Tiers
12-06-2010, 12:04 AM
Some glues DO cause rust on steel. I don't know what they might do to aluminum. Usually it is fumes from the dry and apparently cured glue that does the rusting, I don't know what liquid glue might or might not do.

I found out when the glue I used in a tool case insert rusted the surface of a small straightedge I had just finished scraping-in! The glue had been dry for a couple days at that point. it was some form of white glue IIRC, but might have been a "yellow" carpenter's glue.

In any case, dunk a piece of similar alloy in some glue in a bottle and see. In fact test several alloys. Cheap way to find out.

fredf
12-06-2010, 12:33 AM
What we used at one place I worked (for CA glue) was a device like a paint pot. sit the bottle in side and apply pressure. iirc foot pedal applied pressure, when released dumped air and applied a slight vacuum. would think that a valve on the output line would work as well. was made for gluing . . .

come to think of it the same controller was used with syringes, that's where the vacuum was used, to slightly pull back the piston to stop the flow.

darryl
12-06-2010, 12:47 AM
Yes, I think I will do a test. Weakening of the bottle over time would obviously be dangerous, and I don't want to create that situation. I think at minimum I will coat the inside, probably with epoxy. It won't be hard to do, and I have some on hand. This stuff remains a bit flexible once cured, so it should adhere ok.

The bottle I have is about 3 inches wide and 8 inches tall. Seems just about the right size to swing around by hand all day. Much bigger and it would get tiring. It's just come out of the oven- I cleaned it out and decided to bake the moisture out. Seems I've also baked the paint a little- not a bad thing.

winchman
12-06-2010, 01:37 AM
Find out what coatings they use on the aluminum cans they use for saline solution for contact lens wearers.

http://www.makingthemodernworld.org.uk/everyday_life/img/IM.0922_es.jpg

It's virtually indestructable. I used the cans for mufflers on my gas model plane engines, and the coatings (both inside and outside) would still be there after many hours of exposure to high temperature exhaust gas.

darryl
12-06-2010, 03:21 AM
Too late for that- I've just finished coating the can with epoxy. Mixed up a half oz or so, poured it in, rolled it around, tipped it up to see that epoxy rolled right up to the threads, all around, let it run down to the bottom. Then using a stick, I 'caressed' all the dry spots and the hump in the bottom. I've had the can upside down about four times now, getting the epoxy to flow up and down the sides from top to bottom. Bubbles are all gone, and the coating is finally smooth. It's starting to cure, so no more manipulating.

I will be making the needle valve from stainless rod, which I need to put a perfect point on. That I will do by chucking a length, then supporting the end in a makeshift steady rest, followed by toolpost grinding. That way the point should be quite round, and I'll polish it the rest of the way. I'm considering making the body of the valve assembly from solid pvc. I think I'm going to cut threads for the air inlet adapter directly in the pvc. I'll probably press fit a section of aluminum tubing over the OD of that part so I don't have to worry about the plastic cracking there. It will only ever be under pressure when the air line is momentarily connected. After that, an internal valve will retain the pressure, and a second internal valve will allow the release of pressure. All internal air passages will be small diameter, as will the glue passages. The largest diameter hole where pressure would exist is 1/4 inch. Because of this, the ratio of pvc strength to air pressure will remain high.

The opening to the bottle is about 3/4 inch or so, and I'm thinking to make the valve body about 1 inch thick. I can always shave away areas where strength isn't required- pretty much have that worked out. I'm going to make threads directly on the pvc where it screws onto the bottle. There's room for the o-ring to remain trapped in a groove, same as the existing screw-on valve body is done.

One thing I'm not sure about yet is where to have the adjustable stop to control the glue output rate. It could be behind the trigger itself, it could be behind the needle valve, or it could be that I made the output tube adjustable for length. I think that putting one behind the trigger is a good idea, since it won't matter how much force I pull with, the rest of the mechanism won't have to deal with it. If I put it behind the needle, I'll be putting a lot of strain on the connecting mechanism if I pull the trigger too hard. If I make the output tube adjustable, I'll have to have an o-ring seal there, but otherwise I can pull the trigger all the way, then adjust the tube to seat against the end of the needle (that's zero flow) or anywhere forward of that for an increasingly larger opening (maximum flow). What I'm leaning towards is a solid adjustable stop for the trigger, plus the adjustable output tube.

I intend to drill all the internal passages, intersecting as required, then cap the ends of the holes to seal in the pressure. Since these holes will be 3/16 diameter, some 1/4 inch button head bolts will be used here, with gaskets under the heads. Pvc taps nicely, so I'll use a bottoming tap to keep the length of threading required within workable limits. With the caps removed, all the internal passages will be see-through, so cleaning should be easy.

Because the two passages in the threaded part that screws into the bottle are small diameter, I'll have the option to center drill that part and insert a bolt. This would be for insurance against breakage of that stem, although I don't think that will be needed. If the stem breaks off, there will be two 3/16 holes letting the pressure go. I don't think there's a safety issue there. Worst case the bottle hits the floor, breaking off the valve assembly, and both air and glue escape through those holes. In my mind, I see a pool of glue gushing out onto the floor- a nice mess for me to clean up. Beyond that, the bottle could burst-

Notice I've glossed right on past that potentiality to this- Maybe no need to run the glue dispenser at shop air pressure- it might actually be too much and glue flows too fast with poor flow control, or really finicky adjustment. In that case, I'll add a pressure control valve directly to the side of the valve body. Not hard to do, and it can be adjustable quite easily.

Well, that's the description of the project's design- subject to changes as needed. I'll post pictures of it when done, whether it works out or not. Hopefully some of this will be of interest to some.

batt-man
12-06-2010, 03:59 AM
I was going to suggest that you anodize the bottle (battery acid, water, power supply and a strip of lead or something to hang in the middle) but as you've now epoxy coated it....

J Tiers
12-06-2010, 09:58 AM
So, now, if there is any horrible reaction (which I have no reason to expect) it will be in a neat ring where the threads meet the rest of the bottle!

visions of a "glue water rocket" coating the entire area................;)

vincemulhollon
12-06-2010, 04:09 PM
I'm not concerned about the nozzle design, et al, just the possibility of the pva eating the can, or the can altering the pva. I've looked but I can't find a compatabilty rating for pva with al.

Al is mostly stable in acid and mostly unstable in alkali solutions.

Google for "white glue pH" and they're mostly just barely acidic around pH 6.

johnnyd
12-06-2010, 10:53 PM
If your present arrangement doesn't work out, you might look into a carbonated beverage container/dispenser.
Easily pressurized with CO2 & I believe they are made of stainless steel.

madwilliamflint
12-07-2010, 02:21 PM
I'll post pictures of it when done, whether it works out or not. Hopefully some of this will be of interest to some.

Look forward to it. It's sure interesting to me.

bob_s
12-07-2010, 03:17 PM
Google for "white glue pH" and they're mostly just barely acidic around pH 6.

If neutral is 7, you must mean alkali!