I usually run about 40 cfh

my results

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Great looking welds.

So how does one measure 40 CFH? Do you just use the standard Argon-calibrated flow gauge regulator? My gut tells me that helium would pass through the orifice at a higher rate of flow than argon at the same pressure.

 

Yes an argon flow meter is what I use, you'll also want to get the largest nozzle opening you can on your gun

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Thanks Colindstark. The Multimatic 200 comes with a Bernard gun that has a 1/2" nozzle standard. AFAIK, the largest nozzle available for that gun is 5/8". But since I'm going to be welding inside a 90 deg corner, I'll try the 1/2" nozzle and see how it goes.

 

So I've been doing more digging around and it appears that helium flows at a rate ~3x greater than argon for a given pressure and orifice. So to achieve 40 CFH from a flow-gauge calibrated for use with argon, it appears that I need to shoot for ~13.5 CFH (I'll probably round that up to 15). I'm fairly confident that would work with a ball-style flow meter, but I'm not so sure if it will work with a regulator-style flow gauge.

Any voices of experience out there?

 

I would switch to a flowmeter and be done with it.

 

I do have a floating-ball flowmeter. But it only has two scales: one for Ar and one for CO2. Nevertheless, I agree that it's probably a better option to use it (adjusting for the difference between He and Ar) than using the regulator-style Ar flow gauge.

 

I set mine at 40cfh on an argon flow meter because the helium will float away faster than the argon will.

 

The weld puddle is shielded by the constant flow of new gas from the nozzle, not by whatever gas happens to linger in the work zone. Just as Argon (which is heavier than air) will shield perfectly fine when making inverted, horizontal, or vertical welds, so will Helium when making flat, horizontal, or vertical welds.

The problem with too much shielding gas flow (besides wasting gas... and money, especially for Helium!) is that a high flow rate results in gas turbulence (and possibly a venturi effect) at the nozzle which will bring atmospheric air into the weld puddle. And that is exactly what the shielding gas is supposed to prevent. If, in fact, Helium flows at 3 times the rate of Argon, then setting your Argon flow meter to 40 CFH will result in 120 CFH of Helium flowing through your torch nozzle!

 

Buy a cheap flow meter that checks the flow at the nozzle and set the regulator at whatever... Fixed

 

+1. Seems that would be the simplest solution.

As a bonus, they are handy anyway.
I use mine to verify flow rates of flowmeters and regulators (mig and tig) and to check for proper flow when there is a suspected problem.

 

Just turn it up till it welds good? I don't see the problem.....

 

Actually, "turn it down till it welds good" would probably be better advice, considering that an Argon-calibrated flow meter will flow roughly 3 times the amount of Helium. I spoke to a support technician at Victor and he confirmed concerns. He told me that the conversion numbers they use for calculating flow are 0.85 for Argon and 2.69 for Helium (where dry air is 1.00). So if Helium were flowed through a regulator calibrated for Argon and set for 40 CFH, the actual flow of Helium would be:

40 CFH (Ar) * [2.69 (He)/0.85 (Ar)] = 126.6 CFH (He)

So, in order to get 40 CFH of actual Helium flow from a flowmeter calibrated for Argon, we can calculate the correct setting:

40 CFH (He) * [0.85 (Ar)/2.69 (He)] = 12.6 CFH (Ar)

Therefore, if we put an Argon calibrated flowmeter on a bottle of Helium tri-mix and set it so the flowmeter shows a gas flow of 13 CFH, then we will actually be flowing 40 CFH of tri-mix.

 

Man I priced tri mix today and for a guy that doesn't weld for a living, the cost is outrageous! Praxair quoted me today at $200 for the cylinder and $350 for the gas! I'll just stick to mild steel and aluminum.

 

I really don't understand the welding gas industry. Sometimes it feels like they just make up their wildly-varying pricing.

FWIW, I just purchased an 80 CF bottle of tri-mix (90% He, 7.5% Ar, 2.5% CO2) from Airgas. It cost a total of $240 ($140 for the cylinder, $70 for the gas, plus tax & other fees). Praxair had quoted me $400 just for the gas alone.

 

Hmmmmm I guess my gas supplier takes good care of me because I NEVER heard
of prices that high other than Grade 5 Helium and that has even come down ?

 

All i know is if i go lower on the flow i get a dull gray weld not sugared just gray, and I'm cleared to 3/4 inch P11 material ie 2205 super duplex stainless steel.

 

Thanks for the feedback. I'll run tests beads with various flow settings to see what works best for my equipment.

 

Not to hijack your thread but.
Will tri mix run on a 115V MIG or do I need a bigger machine for tri mix?
I tried SS and tri mix on a WELDPACK 100 and it didnt work

 

I tried SS and tri mix on a WELDPACK 100 and it didnt work

What does that mean, "didn't work"?

 

@ SuperArc - for short-circuit MIG on SS, you should see if your LWS can rip you a jug of 98Ar/2CO2. $350 for the tri-mix is InsaneO, unless they were filling up the tanker showcased in "Mad Max".

 

I found a listing in a Victor regulator data sheet that lists the correction factors, using air as 1.00, as follows:

argon 0.85
CO2 0.81
helium 2.69
nitrogen 1.02

So, if you have a flowmeter in one scale you just need to multiply by the ratio of the ratios (got that?). Example: a flowmeter for CO2 but is now using argon. If the CO2 scale shows 50 cfh, then the actual argon flow would be 50x0.85/0.81= 50x1.05 = 52 cfh

I checked this against my multiple scale flow meter, which gives the following rough ratios:
Ar to CO2: 1.03
Ar to helium: 0.325
Ar to nitrogen: 0.857

Within my eyeball measurement tolerances, this appears to be pretty good correlation to the Victor correction factors.

metalmagpie

 

In general I agree with the conversions posted, however, if you are getting less than optimal results, or going through the gas much much faster than you anticipated, I will drag out my handbook of chemistry and physics and make a calculation of what your density conversion factors should be. That could be referenced to a He scale, a Ar scale, a CO2 scale or whatever.

I believe the floating ball flow meter is called a Thorpe tube flow meter, and has a tapered inner tube, where the ball and the pressure of the gas find equilibrium. An old rotameter would give a more accurate measurement (used in medical applications where there is a need for more precise control of gas delivery, for example in anesthesia). It would be nice to have a rotameter to check the calibration of other meters. Back to the Thorpe tube meter...a couple of things...first they can be pressure compensated or non-pressure compensated. Second, I believe that they are more accurate when there is a downstream resistance to flow (for example a valve in a TIG torch).

I believe the orifice type flow regulator, which reads pressure on the high pressure side of an orifice, is more suspectable to downstream flow resistance, and therefore increase in pressure on the low pressure side of the orifice. I think this type of metering scheme is called a Bourdon flowmeter. Not really a flowmeter, but under the right circumstances, it is close.

Probably the best way to view the operation of a Thorpe vs Bourdon is that the Thorpe (floating ball) doesn't care about downstream flow restrictions, and truly measures flow. Whereas the Bourdon (orifice) meter measures pressure on the high side of the orifice, and assumes that the flow in unimpinged. If it is restricted, then the Bourdon will read high, compared to the actual flow.

Other than the potential inaccuracy of Bourdon meters when there is a downstream flow restriction, I am not clear on effects of temperature, as an example. I will ask around. One of the guys I know is a fluids guy.

I am interested in this because I have a Multimatic 200 and will want to MIG a SS exhaust later this year when the tractor is down for the winter.

I picked up about 25 ESAB R-33-FM-320 regulator/flowmeters (sold some, and kept a handful). What I wanted to do was to have a dedicated regulator/flow meter for each gas I might use. I also didn't have a regulator/flowmeter for CO2. Since CO2 reliefs are slightly different than for inert gases, I figured I was safe with the CO2 regulator. The parts breakdown for the R-33-FM-xxx regulator shows one flowmeter internal "calibrated" tapered tube for CO2, and another for other gases. I have ordered one for other gases (~$18), but don't have it yet, and haven't inserted it into one of the R-33-FM-320 regulators. When I do that, I will also change out the CGA 320 fitting for a CGA 580 fitting.

My final thought is on the gas mix. I have read claims that the actual mixes are / were subject to marketing hype, as to which one worked better than the other. I have not researched that, but it is something to keep in mind.

Regarding pricing, I was recently quoted $72 for 60 cu ft, and $140 for a 125 cu ft refill. The two LWS I use were willing to swap a N2 tank for a tri mix tank, and then back again when I was finished with the tri mix. I like sensible business people who do the reasonable thing.

 

A rough calculation shows with a regulator/flowgauge, with a gauge calibrated for Argon or an Argon CO2 mix, set at 20 CFH will flow about 60 CFH of 90% He mix (about the same difference as with a regulator/flowmeter (one with a ball.) You'll see that with usage! However Helium is lighter and like a balloon flows away from the weld area (unless welding overhead!) so you need more flow rate to get good shielding. 30 CFH set on your gauge is a good starting place, IMO. The resulting ~90 CFH should give good shielding if there is no breeze.