Plumbing your shop for gas

[RichardH]

I'm in the process of running copper line in my home shop for compressed air, and I'd like to hear what folks think of doing the same for welding gases.

I'm thinking probably 2 lines eventually - one 75/25, and one argon. Pressure regulator on the cylinder feeding the line, and flow regulator at the back of the welder. I have a couple work areas - one indoors, one outdoors, about 75' apart, where I'd plumb the gas and electrical hookups.

Thinking being, I'll eat the up-front cost for 300cf cylinders to be cheaper in the long run, but they need to stay in one spot. Copper line means I don't need to drag hose around, I don't need to waste a lot of gas priming the line each time I setup, and the welding cart is loads lighter. (Maybe my math is off, but it looks like it'd take at least 13cf just to prime a 100' 1/4" hose - much more depending on the pressure.)

If this isn't too crazy, then what's a good line size to run? Wading through the online calculators, it looks like 1/4" i.d. line could handle up to about 30cfh - but is that too tight? I'm reluctant to oversize the piping because it'll bleed off when the tank is closed and waste more gas to recharge the line at next use.

Cheers,
Richard

[geezer]

I doubt that is a good idea,,,having a tank in some corner of the shop means you have to run over to shut it off and or adjust the flow,,if it was a good idea everybody would be doing it,,,it's nice to see someone thinking outside the box,,,

[DaveO]

Back in the day I worked at a LWS that also repaired regulators and torches; the repair guy used a sandblaster to clean exterior surfaces. The compressor was on the opposite side of the warehouse and we eventually moved the sandblaster into the enclosed repair shop. We ran PVC pipe to supply that sandblaster- would that work for you, possibly save a few bux?

[Rambozo]

Big welding shops used a piped supply, but I'm not sure it makes sense for a home shop. 1/4" tube @ 50psi would do the job, if it's not too long. You could use copper or even poly tubing rated for that pressure. A lot depends on if your welder will be parked in one place, most of the time, or always be moving, and how far. As you say, you would lose a lot of gas every time you had to open the system, to purge it.

[Rambozo]

Back in the day I worked at a LWS that also repaired regulators and torches; the repair guy used a sandblaster to clean exterior surfaces. The compressor was on the opposite side of the warehouse and we eventually moved the sandblaster into the enclosed repair shop. We ran PVC pipe to supply that sandblaster- would that work for you, possibly save a few bux?

PVC is a big no no for compressed gases, even air, because of the way it fails (think plastic shrapnel). Virtually every shop I've worked in has used it, back when it was legal, and they all have horror stories of the day when something exploded.

[zoama]

(Maybe my math is off, but it looks like it'd take at least 13cf just to prime a 100' 1/4" hose - much more depending on the pressure.)

Cheers,
Richard

It would take 59 cubic inches to fill a line 1/4" x 100' or about 1/29th of 1 cubic foot (1728 cubic inches). Pressure is irrelevant.

[Rambozo]

It would take 59 cubic inches to fill a line 1/4" x 100' or about 1/29th of 1 cubic foot (1728 cubic inches). Pressure is irrelevant.

Pressure of a compressible gas is totally relevant for that calculation.

[zoama]

Pressure of a compressible gas is totally relevant for that calculation.

Any pressure great enough to escape the bottle would purge the line. If I'm wrong please explain.

[Rambozo]

Any pressure great enough to escape the bottle would purge the line. If I'm wrong please explain.

True, as long as you did not let the pressure increase. But it will take the volume of the line for every 14.7 psi to bring it up to that pressure in the line. Then if you open the line you will lose that pressure and have to replace it. So for 50psi line pressure you will need aprox. 4.5 times the line volume of gas to get that pressure.

So for the example: 1/4" ID 100' hose: it would be about 265 cubic inches of gas. Or just over .15 cubic feet, not counting hose expansion due to pressure.

[zoama]

True, as long as you did not let the pressure increase. But it will take the volume of the line for every 14.7 psi to bring it up to that pressure in the line. Then if you open the line you will lose that pressure and have to replace it. So for 50psi line pressure you will need aprox. 4.5 times the line volume of gas to get that pressure.

So for the example: 1/4" ID 100' hose: it would be about 2650 cubic inches of gas. Or just over 1.5 cubic feet, not counting hose expansion due to pressure.

Any pressure great enough to escape the bottle would purge the line. The line would contain a higher volume with increased pressure but that would remain behind a quick coupling and not come into play.
As the bottle empties, the line and bottle pressure would eventually equal atmosphere together.

What formula are you using to calculate the volume ?

[Rambozo]

Any pressure great enough to escape the bottle would purge the line. The line would contain a higher volume with increased pressure but that would remain behind a quick coupling and not come into play.
As the bottle empties, the line and bottle pressure would eventually equal atmosphere together.

What formula are you using to calculate the volume ?

With good couplings you would not lose much, but if you opened the line or lost the line pressure due to leaks, that is what it would take to refill the line to pressure. Some shops lend themselves to plumbed lines, others to bottles on each cart. I prefer keeping a few different sized bottles around. Portability and backup for when I forget to get something filled.

I was so busy trying to copy the math symbols into that post, (total fail) I misplaced a decimal. You caught me before my edit.

[RichardH]

It would take 59 cubic inches to fill a line 1/4" x 100' or about 1/29th of 1 cubic foot (1728 cubic inches). Pressure is irrelevant.

You are correct - my math was off by a factor of 12 (I divided by square feet instead of cubic feet). And I agree the pressure is irrelevant to the volume of the line itself, and the amount of gas needed to purge it.

But based on experience with my air compressor, I expect that a pressurized line will bleed out overnight to equalize with atmospheric pressure, so it'll need to be re-pressurized at the next use. That amount is "wasted", and an oversized line wastes more. (I wouldn't expect it'd need to be re-purged, since the line didn't get contaminated, it just lost some content.)

As you point out, the math is not as bad as I thought. I'll need to measure the regulator's output to see what pressure it lets the output line charge to.

Cheers,
Richard

[RichardH]

1/4" tube @ 50psi would do the job, if it's not too long. You could use copper or even poly tubing rated for that pressure.

It seems like 1/4" should be plenty, considering what I can push through a hose with an air compressor (even at 50 psi). Poly / braided tubing isn't an option outdoors here - the UV + heat + low humidity destroys plastics. I'll just need to look further than Home Depot to source 1/4" i.d. rigid copper.

In the larger shops you've seen with piped gas, did they use a flow regulator at the back of the machine? That seems to be more practical (and more consistent), even with a long hose.

Cheers,
Richard

[Rambozo]

It seems like 1/4" should be plenty, considering what I can push through a hose with an air compressor (even at 50 psi). Poly / braided tubing isn't an option outdoors here - the UV + heat + low humidity destroys plastics. I'll just need to look further than Home Depot to source 1/4" i.d. rigid copper.

In the larger shops you've seen with piped gas, did they use a flow regulator at the back of the machine? That seems to be more practical (and more consistent), even with a long hose.

Cheers,
Richard

Oh yeah, AZ. Not much will survive outside there. Maybe not even aluminum tubing, but there is that and copper refrigeration tubing that will work and can be bent to suit, pretty easy. For sure you will need your needle valve and flowmeter near the machine, or you will have one hell of a startup blast. Some shops just have flowmeters for each machine, others have a regulator and flowmeter, so I guess they are running higher line pressure to get more machines on the same size line. I never saw a line pressure gauge on that system, so I'm guessing. On the ones with just flowmeters they were running 50psi. You need a minimum of 25psi, but most regulators are from 40-80psi. I don't have an Everlast regulator, so I'm not sure what they come set to. A few brands are adjustable for both pressure and flow. I would strive to get a leak-free system if you plan on going that way. If the system bleeds out, then it will most definitely draw in air as it heats and cools. Another AZ specialty. And the amount of argon required to purge all the air out of a tube will surprise you. For welding stainless steel pipe, the specs call for 5 times the pipe volume to purge enough oxygen to get a clean weld with a purge monitor. Argon is heavier so you might want your tube to rise from the bottle to the bleed point. That will help, but it will still take several complete changes of gas to purge all the O2 from the lines. The last thing you need as a new welder is contaminated gas, you will chase your tail trying to figure out why your welds don't come out right. Depending on where your power outlets are, you are still tethered to them, so unless there is some compelling reason to have your bottle far away, or your shop is huge, it seems kinda overkill to plumb for welding gasses, especially for just a few machines, but it's up to you. I will admit that the small size and weight of inverters dwarf a 330cuft bottle, unlike the older transformer machines where the added weight of a bottle was negligible.

[DaveO]

PVC is a big no no for compressed gases, even air, because of the way it fails (think plastic shrapnel). Virtually every shop I've worked in has used it, back when it was legal, and they all have horror stories of the day when something exploded.

Yikes, well, not PVC then.

[Kempy]

I plumbed my shop with PEX piping it will take a lot of heat and cold temperatures and 300 psi. You can get almost any fitting to fit it. I run 175 psi line pressure in 3/4" line and drop offs of 1/2" all over the shop. It is better then copper because you can add any time to the system in minutes. it is cheaper then copper and you can run any length with no joints.

[RichardH]

I would strive to get a leak-free system if you plan on going that way. If the system bleeds out, then it will most definitely draw in air as it heats and cools. Another AZ specialty.

Ah, excellent point - I hadn't considered that it'd suck in outside air when the temp changes. I'm starting to lean toward the idea of putting a ball valve in front of both quick-disconnect outlets, which would take care of the bleed-off issue. I'll only have 2 outlets, so not a big deal to add.

Argon is heavier so you might want your tube to rise from the bottle to the bleed point.

Excellent point, thanks. Pretty much the inverse of what I did for condensation in my air lines.

Depending on where your power outlets are, you are still tethered to them, so unless there is some compelling reason to have your bottle far away, or your shop is huge, it seems kinda overkill to plumb for welding gasses, especially for just a few machines, but it's up to you.

Yup. I'll have electrical in the same two spots. The work areas are pretty fixed, but my outdoor pad is about 75' from my indoor shop. The local plumbing supply has 3/8" o.d. (1/4" i.d.) rigid pipe and fittings, and it looks like the whole project should be under $200.

Thanks!

[Rambozo]

I plumbed my shop with PEX piping it will take a lot of heat and cold temperatures and 300 psi. You can get almost any fitting to fit it. I run 175 psi line pressure in 3/4" line and drop offs of 1/2" all over the shop. It is better then copper because you can add any time to the system in minutes. it is cheaper then copper and you can run any length with no joints.

PEX-AL-PEX is rated for air and works great, except it is not UV stable, so it must be covered when used outside. It should even be covered under fluorescent lights, but no one does. The damage would take a very long time to be a problem, inside. Maybe if you have lots of HID lights you would have an issue after years and years. But outside in AZ, I would not give it much time at all. The sun is crazy in the desert, especially at altitude, does all kinds of strange stuff to materials that last fine anywhere else.

[sportbike]

How much welding do you plan on doing?

I'd bet you will have way more headaches with a hard plumbed system than just having local bottles.

The only places I have ever seen hard plumbed welding gasses are large manufacturing facilities that have argon stored as refrigerated liquid in a central location.

If you are the only user and you aren't welding 8 hrs every day, I don;t see the benefits. Just opens you up for way more potential gas issues.

[Kempy]

PEX-AL-PEX is rated for air and works great, except it is not UV stable, so it must be covered when used outside. It should even be covered under fluorescent lights, but no one does. The damage would take a very long time to be a problem, inside. Maybe if you have lots of HID lights you would have an issue after years and years. But outside in AZ, I would not give it much time at all. The sun is crazy in the desert, especially at altitude, does all kinds of strange stuff to materials that last fine anywhere else.

Your right it is not UV stable but most plastic are not UV resistant but up in the now cold part of the world copper pipe outside with water in it will split but the PEX will not. With this ice storm we are having and power out for a week the PEX will hold up but anyone with copper pipe will be calling the plumber. I still like the cart and the bottle with it, some of my carts I put two bottles one 25/75 and one 100% Argon.