Gas mixing valve Idea-Need your input!

[hooda]

So Folks, Jakeru has a thread in the On Road Fabrication section on welding aluminum pipe with Argon/Helium mix (I recommend that you check it out, if for nothing but to see his beautiful welds). I was posting a question on that thread because I don't understand how he gets the 2 gases to mix when they are entering the stream at different rates. It doesn't make sense that the higher rate gas (Argon) doesn't just back up the lower rte gas (Helium) At some point a light went off in my head, and I got an idea. I still don't fully understand HOW his system is working, but I don't question that it IS working. Either way, Here's the idea: How about using an ordinary kitchen faucet as a mixing valve for Argon and Helium? I have seen some Good quality faucets lately, the single handle type, that I believe would do a bang up job of making sure the gases are thoroughly mixed by the time they enter the torch hose. Think of the fact that when you turn on the water to wash your hands. You can adjust the hot/cold ratio to suit your taste, and by the time it exits the faucet, you can't feel "hot on the left and cold on the right" you just feel warm water. As Jake explained in his system, he has 2 regulators that are set to identical pressure, where I get confused is if they're at the same pressure, how does one regulate the two for different rates. I think my confusion is in assuming that he's using flowmeters, not regulators and I have the 2 confused?. Either way, My idea would be to have REGULATORS on each tank, set to identical pressures, with Argon going to the cold side of the faucet, and Helium going to the hot side ("H" for helium) Then attaching the actual Flowmeter to the output side of the faucet, and on to the torch. That way, adjustment of the ratio of Ar to He would be as simple as moving the handle left or right as needed. If I have time left before the contest ends, This will become a project for me, to get the system assembled (bracketry, etc). But in spite of that, I welcom anyone's input as th whether you think this idea will work. Thanks all, And especially thanks to Jakeru for getting the idea going.

[67cudafb]

I don't quite get the kitchen faucet idea when you can get brass y fitting and gas valves to do this. You do need oneway check valves so gas doesn't backflow into the lower pressure tank. Why both gases flow is like a siphon type air gun works when you open the valve the air flow creates a vacuum to draw lower pressure gas into stream and mix together but when you close the valve the higher pressure will try to backup into lower pressure tank hence the need for oneway check valve.

[Rivets]

.....I was posting a question on that thread because I don't understand how he gets the 2 gases to mix when they are entering the stream at different rates. It doesn't make sense that the higher rate gas (Argon) doesn't just back up the lower rte gas (Helium) At some point a light went off in my head, and I got an idea. I still don't fully understand HOW his system is working, but I don't question that it IS working....

Maybe if one thinks about an OA torch it becomes clearer ?

I set my acetylene regulator at 5 psi and the oxygen one at 10 or 15 psi. The torch valves regulate the flow of each gas and it all flows out the tip.

In fact, an OA torch valve body would probably make a good mixer for Ar/He or Ar/CO2 for that matter.

FWIW,
rivets

[parkour]

Pressure is voltage, and rate is amps. They're two separate things.
I've not read Jakeru's thread, just this one. If is he has two regulators set to same pressure, the valves (he used) will allow you to control the rate at which gas leaves the cylinder at constant pressure ahead of the valves. The regulators do not even need to be set to the same pressure. A pressure regulator is a constant pressure device (pressure regulator.) Rate can change independently of pressure. However fast you let gas out of the cylinder, the regulator will increase the pressure to maintain the set pressure at that rate (within its mechanical limits).

Whether or not you need a check valve depends on the design of the regulator. Some regulators are designed to dump excess pressure overboard when you reduce the pressure setting. A regulator set for O/A will NOT be designed this way for obvious reasons. If you're using a flow meter, the simplest and thus cheapest design is to not dump, so this will work just fine with a flow meter. A "regulator" can be tested simply by adjusting the pressure up, and then back down. If you hear a hissing sound and the pressure reading goes down, you will need a check valve, but if you hear nothing and the pressure remains at the high point, you will will not need a check valve.

This whole check valve thing only matters when the gas solenoid is off. If the solenoid is on, the atmosphere will present 0 psi back-pressure since the regulators are referenced against the atmosphere. (psig -gage, not psia -absolute) So no gas will back flow into the lower set regulator since it is obviously at a pressure higher than atmosphere. When the solenoid is off, the higher pressure regulator will cause the lower pressure regulator to dump pressure overboard if it is designed to dump over pressure. Air compressor regulators are commonly designed this way. I am guessing that compressed gas regulators are NOT designed this way. You're probably good to go. The easiest way to test this is to just hook two regulator/flowmeters together and see if one hisses from gas dumping overboard when the other is at a higher pressure setting. Only with inert gases.... no oxygen or flammables. You could blow shop air into the regulator's output if you have *clean* shop air.

What you want to do will work just fine with flow meters, regulators, or a combination of both (provided above condition is met with the "regulator" that it does not need a check valve) Using two flow meters (ball or gage style) would be easiest, but regulators will work also. You can most likely just use two gas cylinders and two "regulators" of whatever kind you have laying around or can get the cheapest, a plain old brass T fitting in the hoses, and you're golden. If you have two flow-meters, you can set it to your desired flow and ratio. If you have regulators (that read in psi), you can determine the ratio. If you have one that reads flow and one that reads psi, you wont (easily) be able to determine flow or ratio.

You do not need additional valves, unless you want the ease of a single handle to adjust the flow and mixing. You can simply use the knob to adjust pressure or flow on the regulator or flow-meter, and you're set.

Rejoice. its a very simple process.
The gases will mix in the hose just like the water does in the faucet.

[DVA]

Do not worry about the pressure as long as you are using meters that measure the flow. You will need to check the set points of the regulators with the gas flowing to obtain the proper mixing desired. Depending on the tanks size and the time welding the flow may need to be adjusted due to decreasing tank pressure as the gas flow rate out of most regulators reduces as along with the tank pressure.

Check valve is a good option to have but not necessary as long as you are using similar type regulators as they should be rated for the same pressure so they will not damage each other.

I would not worry about mixing of the gasses as the flow in the lines is most likely turbulent and the long skinny lines will mix the gases. If you are concerned with mixing, install an in-line check valve on the single line section of tubing, as the check valve design will assist with mixing the gasses but is un-necessary in my opinion.

[hooda]

I guess I'm disappointed that there's lots of talk about different arrangemente fo check valves, pressure, regulators, and theory, but I still think the faucet idea rocks, and I have made tha desision that, whan I get time, I WILL be putting together a Single handled, Kitchen Faucet based, gas mixer. I will obviously post the results here on my FAVORITE forum

[ogorir]

the faucet will probably work, although they're designed for a lower pressure, you might have a seal blowout at some point. other than it being cool, I don't really see the point of buying 2 regulators, flowmeter, and a faucet over a pair of flowmeters and a y-connector. you have the same adjustability with that setup with less complexity. only drawback is the overall flow is reactive, in that you can't set it directly with one knob. I guess you could add a 3rd flowmeter and gain the same thing, but I don't think it's necessary. just tryin' to save you a buck or two, mate!

[DaveO]

How exact do the proportions of He and Ar have to be to perform a quality weld? Even though we all have that favorite spot on the shower valve that delivers water at just the right temperature, finding the exact spot on the He/Ar setup may take a lot of experimenting and may not be immediately or easily repeatable from session to session.

[hooda]

How exact do the proportions of He and Ar have to be to perform a quality weld? Even though we all have that favorite spot on the shower valve that delivers water at just the right temperature, finding the exact spot on the He/Ar setup may take a lot of experimenting and may not be immediately or easily repeatable from session to session.

Without going back to do the research, I believe that Jakeru was getting excellent results at about the 12% He level, which would be a significant cost savings over buying pre-mixed 75%ar/25%He. That is of course assuing that one fell in love with the idea of using Helium on a regular basis. I believe that people only use helium when absolutely necessary. I have a thread on this forum from waqy back where I got a bottle of 75%HE/25%Ar to try to weld a cylinder head, and due to my inexperience more than anything, it did NOT go well. Bunner of it is that my dad was involved, as I didn't at that time have my own account at the LWS, and he raised a stink, so I turned in the 90% full tank rather than listen to his yammering, so my experiments with Helium were put on hold. As soon as I get a TIG machine again, I will resume experimenting. As far as consistency, my educated guess is that since my shower faucet ends up at the same 2 spots relatively consistently (regular shower, and HOT shower), I think there will be a spot or 2 on the faucet in this application that I'll be able to mark as the general start point, and fine tune from there. If you're familiar with the movie "Spinal Tap" you'll remember that Nigel's amps are custom made to go up to "11" for when you need that little xtra oomph to put it over the top. I look at the addition of Helium as turning your TIG welder up to 11!

[jakeru]

I find myself mixing in some Helium for when I weld aluminum about 1/8" or thicker, especially if extra penetration is desired. I don't do it for stainless or mild steel. But on aluminum, the He % allows concentrating the heat more, and I find I can often get away with 1/16" tungsten (or a "sharper" tip grind), where with argon I'd have needed a 3/32" tungsten (and/or a "blunter" tip grind.) This makes a deeper, narrower puddle which is often a good thing. There can be less heat input into the work. Being able to penetrate deeper saves me prep work (don't need to bevel as deeply to get the same penetration.) And as a result, I find I can get my aluminum jobs done more quickly. What would have normally taken me 45 minutes, I am getting done 10 minutes quicker.

So really, I use some Helium % more often than not on any aluminum work.

Since I often run a light arc over the surface before I start to weld, to check the cleanliness of the surface (especially on repair jobs where things aren't clean to start with, and dirtiness will be detected and can corrected before porosity is introduced), I like to use a small enough He % that it doesn't adversely affect arc starting and stability under the light arc needed for cathodic etch cleaning, but yet still give me the heat boost I want when it come time to weld, and penetrate. So I put it at a small He% flow, so I don't have to vary the gas mix after cathodic etch cleaning is done, before I go for the deep puddle melting action.

I often find myself running about the minimum He flow I can get away with while having the mix remain stable. It is not totally scientific, and I am still experimenting, but would say, maybe it's somewhere in the ballpart of 2-5cfh Helium. Compared to maybe 10 cfh argon if using a #5 cup, to 12-15 if using a #6 or with more stick-out.

If the He % varies after the solenoid opens (I can hear it in the sound it makes coming out of the cup), I can abort the arc start and keep the gas flowing long enough (say, 3-4 seconds) to let the mix stabilize before I triggering the arc start. If the mix is varying and I start the arc, it can make hard arc starts and unexpected heat input until it stabilized.

Best of luck...