Welding Tips and Tricks

I'm trying to order a 125 for CO2 and another 125 for Argon as backup cylinders but the sales person at Airgas can't answer my question.

Question: Is it possible to increase the amount of gas in a 125 to some permissible maximum per gas type? The cylinders can take pressures much higher than the 1000 for CO2 and, I believe 2000 for Argon I got last order.

I ask because I have these things shipped to me from Medlay Florida to the island of Roatan. The shipping charges and fees are many many times the cost of the gas. I'm trying to get as much gas per shipment as possible.

Airgas probably won't fill to higher pressure on request. Can you go to 330 cu ft cylinders?

Bill,

CO2 and Argon are very different animals in how they are stored, thought the bottle appears the same. I have Air Products' "Gas and Equipment handbook in front of me. 100% CO2 is stored as a liquid under it's own vapor pressure which limits the bottle's capacity to it's volume, not it's pressure rating (838 psi at 70F), and the fitting on the bottle valve is most likely a CGA-320. I do NOT know the pressure rating of the container, and would not recommend having it re-valved and attempting compressed gas pressure.

On the other hand, bottles for compressed gasses such as argon, or even C25 (the CO2 dissolves in the argon, so doesn't liquefy) typically are considered full at 2400 psi at 70F. If they're delivering, you can have a 10% overfill, for 2640 PSI at 70F. (Both these bottles will have a CGA-580 valve fitting.)

I hope some of this helped.

Steve S

Poleframer: The 125's are large and heavy enough. I have two of them on the back of my welding cart. Don't want to go to larger cylinders.

Otto Nobedder: Are you saying that the CO2 cylinder is full (nearly) of liquid CO2? If that's the case I can understand why no more would fit. As for the Argon, I don't know what these brand new tanks are rated for, but my aluminum scuba tanks are over 3000 PSI of dry air. What limits the pressure a supplier is willing to go to for a particular gas? Just curious.

I'll ask if they can bump the pressure a bit on the Argon as you mentioned.

RoatanBill wrote:Poleframer: The 125's are large and heavy enough. I have two of them on the back of my welding cart. Don't want to go to larger cylinders.

Otto Nobedder: Are you saying that the CO2 cylinder is full (nearly) of liquid CO2? If that's the case I can understand why no more would fit. As for the Argon, I don't know what these brand new tanks are rated for, but my aluminum scuba tanks are over 3000 PSI of dry air. What limits the pressure a supplier is willing to go to for a particular gas? Just curious.

I'll ask if they can bump the pressure a bit on the Argon as you mentioned.

the limit would be both the tanks and the pump they are using to fill them too..

persay if there using a 2500 PSI pump.. there is no way your going to get above 2500PSI with that pump.. and i would guess they have pressure relief valves to them so they might be why they cant go above a certain point. still worth a ask though if they can do a little more.

basically think of the CO2 tank like a propane tank.. you need space for it to boil off into if you dont.. it wont end well at all.. my dad got one that was over full one time and it froze up a few times until it emptied some. also you would be at risk for loosing pressure and thus gas flow if it was too full because there is not enough space for the CO2 to boil off. look up over filling propane cylinders as there is more info out there on this then Co2 more or less the same concept going on with the Co2 as there is with propane.

RoatanBill wrote:but my aluminum scuba tanks are over 3000 PSI of dry air. What limits the pressure a supplier is willing to go to for a particular gas?

Your aluminum SCUBA tanks were originally designed for the 3000 psi rating. SCBA tanks (firefighting) are often 4500 psi, but again they were designed and built from the beginning for those pressures. The design of the cylinders and therefore the operating pressures are all primarily set by DOT specifications. Not allot of leeway for your local supplier to make changes.

Good Luck.

Just curious..

Is there no gas seller in the US region yet that carries the newer style 300bar/4350psi bottles like are getting more common here in Europe?

Gives a nice boost in the usable gas volume for the same size bottle.

Eg: http://www.linde-gas.com/en/products_an ... index.html

(also composite instead of steel, so lot lighter..)

BYe, Arno.

There's almost a monopoly on who sells gas. There's no reason to upgrade their "service" since there's nowhere else for people to go.

I phoned the US from Roatan to speak to my Airgas sales person. I was told I couldn't speak to her and just send her an email about what I wanted, I asked to speak to a different salesperson and that was denied; I had to go thru someone unavailable by phone and had to rely on email. They can get way with this because they are really the only game available.

I got a rude return email, replied to it and haven't heard a word since. A 5 minute phone conversation could have taken care of my needs. Now it's days later and I have no idea where I stand.

Arno,

That is a very cool design. One thing that I looked for and couldn't find was what is the lifespan on the GENIE cylinders. I am not familiar with the European testing requirements for high pressure cylinders, but the US DOT requires regular hydro-static testing, and on the Kevlar wrapped 4500 psi SCBA cylinders there is a maximum allowed lifespan of 15 years I believe. So whether or not the cylinder can pass the test at 15 years it is scrap. This really adds to the cost of unit compared to aluminum or steel that can go for many more years.

Thanks for sharing that one.

Anyone know of a gas supplier other than Airgas around the Medley / Miami Florida area that understands what service is and might have these higher pressure capacity cylinders? My one and only Airgas order a few months ago was such a poor experience that I'd jump at the chance to find a different supplier.

You can give these guys a shot. I've used their location here a few times and they're always good.

http://www2.mathesongas.com/storeLocato ... pt=4&ra=25

That's a tough spot you're in. Hope you're able to find someone to help out.

Arno wrote:...Is there no gas seller in the US region yet that carries the newer style 300bar/4350psi bottles like are getting more common here in Europe?...

While I haven't seen the composite bottles yet, I have ordered a nitrogen cylinder that could be filled to 4500PSI. I think the MAWP on it was 6000, but regulations restricted it to 4500. I also never used it. It proved a waste of time, as the idea was to pre-charge a system for a 9680psi test, and the pump we had for the job could accomplish the "pre-charge" faster than setting up the bottle then swapping in the pump.

Steve S

airrj wrote: So whether or not the cylinder can pass the test at 15 years it is scrap. This really adds to the cost of unit compared to aluminum or steel that can go for many more years.

The composite ones are fairly new and specialised though and mostlly meant for easier portability. Fairly expensive too, but could probably mean the difference between being able to reach some locations or not.

They do tend to have a hard life being lugged around a lot (which is also why the protective pieces are on the top and bottom), so I suspect many of them will already get damaged enough in their lifecycle that they won't even need to last that long.

Also in many cases they are operated on an exchange/rental basis, so the end user doesn't really see the lifespan (or lack thereof), but they just end up more expensive to rent if they need to be replaced sooner..

Plain steel cylinders are still the norm though, but there the 300bar units are making inroads too.

Bye, Arno.

The 5 year hydo test has three outcomes, scrap, safe for indicated pressure and plus. The test involves measuring deformation of the cylinder under pressure and then measuring the yield volume after pressure is relieved.

Plus means 10% overfill pressure is allowed. My rudimentary gouges show 2500 psi. There is still a generous safety factor.

Steel at 2265 indicated lasts a very long time. I've had oxygen cylinders from the 1940s come through..lots of hydro stamps for sure.

If it works, why not?

I have a favorite bottle I use for helium, exclusively, for helium leak testing. It's original test date is March 1919, and the neck ring reads, "Army Air Service Balloon."

It's currently out of date, and I intend to have it retested in March of 2019, and have the recertification date stamped directly under the original test date, for a "century cylinder".

Steve S

Otto Nobedder wrote:I have a favorite bottle I use for helium, exclusively, for helium leak testing. It's original test date is March 1919, and the neck ring reads, "Army Air Service Balloon."

It's currently out of date, and I intend to have it retested in March of 2019, and have the recertification date stamped directly under the original test date, for a "century cylinder".

Steve S

That's pretty sweet man