Home fill station for dummies?

[rjack321]

If I was doing open circuit and had a home compressor, an old membrane O2 generator would be in play. The bad part is with a rebreather the Argon accumulates. Displaces the other inert gasses in the loop. I have to deal with that when I travel. But I don't need to deal with it at home. Bottles of Aviator O2 are cheap enough to get refills on.

I end up with industrial O2. My supplier doesn't do aviators and expects a prescription for medical (plus its double the price and doesn't come in larger bottles). At least for my supplier, industrial gases get one vacuum pulled at the plant vs 2 vacuums for medical O2 and UHP helium. The industrial helium is still 5x 9s.

Sleuthing out exactly what your local gas supplier has, how they treat owner vs rental vs leased bottles, what they call the gas inside, and if they will or won't freak out about you breathing it requires strategic questioning and some anonymous phone calls and detective work.

Things my supplier (a chain of welding shops but the gas itself is from airgas) has/doesn't have
Leased bottles, only for business accounts
Owner bottles, yes but has to be unambiguously not owned by a competitor, these are exchanged, you don't get "yours" back. They don't care about hydros.
Rental bottles, yes with a CC deposit, don't expect to keep it for months. But if you had house guests and needed extra gas for a week this is a tactic
Balloon grade helium or anything cut with air or O2, nope
UHP helium, yes for ~double the price of industrial
Industrial = UHP minus an extra vacuum at the fill plant and a certificate of analysis
USP helium, no
USP medical O2, yes with prescription
Industrial O2, yes minus the double vacuum. Otherwise from the same source as USP o2
300cf, 2400 psi O2, no
300cf, 2400 psi helium, usually
250cf o2 and helium (2100-2200psi), reliably even in peak shortage times. They always had rental and leased helium but in the worst of the shortage 3 yrs ago didn't have owner 250s of helium sometimes. They had no owner 300s of helium for about a year, airgas was only filling established long term customers.

All pricing initially is the full "cash" price. If you buy a bunch you qualify to negotiate that down. On CCR I no longer buy enough to qualify for any kind of quantity discount. I know some of my local LDS's pay half what I pay. But I use ~150cf of helium a year and they use 2x that in a week (or more). Likewise I use maybe 80cf of O2 a month, an LDS selling nitrox uses 2-10x that in a day.

 

[BoltSnap]

industrial gases get one vacuum pulled at the plant vs 2 vacuums for medical O2 and UHP helium

What does "one vacuum pulled" or "2 vacuums" mean in this context?

 

[rjack321]

What does "one vacuum pulled" or "2 vacuums" mean in this context?

They slurp out any gas residuals before refilling them. All gas plants (at least in modern countries) do this, if there is 200psi of O2 left in a tank they don't just refill on top of that fill after fill.

So they draw a vacuum on all tanks in the refill rack. How much of a vacuum I don't know, 2psi? 15psi? 100psi? Not sure honestly and probably depends on the facility

For gas with USP, UHP and/or other certificates of analysis they do that twice.

 

[rob.mwpropane]

They slurp out any gas residuals before refilling them. All gas plants (at least in modern countries) do this, if there is 200psi of O2 left in a tank they don't just refill on top of that fill after fill.

So they draw a vacuum on all tanks in the refill rack. How much of a vacuum I don't know, 2psi? 15psi? 100psi? Not sure honestly and probably depends on the facility

For gas with USP, UHP and/or other certificates of analysis they do that twice.

We pull a vaccum on tanks (propane obviously) of -27.5 because it causes the moisture to boil off in the tank and then there's no question it's dry.

Not sure if there's any correlation, just figured I'd share.

 

[rjack321]

We pull a vaccum on tanks (propane obviously) of -27.5 because it causes the moisture to boil off in the tank and then there's no question it's dry.

Not sure if there's any correlation, just figured I'd share.

yeah good point, that might be a minimum vacuum for o2 and helium tanks.

At the time I called the guy at the "specialty gas division" of my otherwise welding oriented local franchise I didn't think or care to ask. I was really trying to figure out: 1) what "industrial" helium was and if it was clean enough to breath. and 2) if there was any risk of acetylene being in the industrial O2.

If the last user didn't have check valves on their torch, and the O2 ran out first, and there was still acetylene flowing, and the tanks were not vacuumed - if all of those flaws align then yes there could be acetylene in the O2 bottle. Except even ppm levels of acetylene stink something fierce and its hard to miss that. So I decided the industrial O2 from them had enough safeguards on it to use for diving.

 

[broncobowsher]

Well that won't happen. Acetylene takes a very special cylinder. The acetylene is actually dissolved in acetone in the cylinder. And any of the fuel cylinders will have that CGA valve (I forget the series). Propane (the old bottle style) is the same left hand thread as Acetylene.

Oxygen has it's own valve. To use Oxygen with anything else they would need to change the valve, and the cylinder must be emptied to do so. Simply put, they don't change oxygen cylinder to anything except oxygen unless they really have to. Lots of labor to change the valve and paint the tank the correct colors.

Inert gasses are a lot more interchangeable. Helium or Argon both use the same valve. But the tanks are different paint schemes. So still not changing them around.

No gas supplier wants a reputation for a bad gas mix. Have you ever heard of one? Not knowing what a customer may have done before returning a cylinder the simple and safe thing for any gas supplier to do is vent, vacuum, then fill. That way they know exactly what they are putting in the cylinder. If they are selling Argon to a window manufacturer for insulated windows and there is some Helium mixed in, that would kill the thermal performance of the windows. That would be a big warranty claim for the window manufacturer for the wrong gas supplied. Any shop doing aircraft repairs and the weld gas isn't correct. Think of all the other industries that use special gasses. It's way more than just welders and divers buying this stuff.

 

[Miyaru]

From other divers I heard stories that companies refused to supply when they heard it was for diving. I must have been lucky: a couple of years ago the account manager from a gas supplier called me back and I explained the concept of trimix to him. His concern was breathing 100% helium - which is never the case. Anyway, he opened a business account for me and now I get helium straight from the gasdepot.

Color coding and valve connections are not the same worldwide. Although color coding has been standardized in the EU, connections for oxygen still differ from country to country.

Tank on the left is oxygen, shoulder color white, body color white (RAL9010)
Tank next to it is helium, shoulder color brown (RAL8008), body color grey (RAL7037)
Tanks in the back are compressed air, shoulder color green (RAL6018), body color grey (RAL7037)
Tanks on the right are compressed air as well, shoulder color white with a black ring.

There's no difference between the tanks, however the standard colors used in scuba diving are white with a black ring. When tested at the hydro facility, the tanks get a 5-year stamp according to the country's law on pressure containers. But....paint the tank in grey/green and it becomes a technical gas, and then the tank gets a 1-year hydro stamp according to European law.

Attached pdf gives an overview of color codes for other gasses.

 

[rddvet]

From other divers I heard stories that companies refused to supply when they heard it was for diving. I must have been lucky: a couple of years ago the account manager from a gas supplier called me back and I explained the concept of trimix to him. His concern was breathing 100% helium - which is never the case. Anyway, he opened a business account for me and now I get helium straight from the gasdepot.

Color coding and valve connections are the same worldwide. Although color coding has been standardized in the EU, connections for oxygen still differ from country to country.
View attachment 629083
Tank on the left is oxygen, shoulder color white, body color white (RAL9010)
Tank next to it is helium, shoulder color brown (RAL8008), body color grey (RAL7037)
Tanks in the back are compressed air, shoulder color green (RAL6018), body color grey (RAL7037)
Tanks on the right are compressed air as well, shoulder color white with a black ring.

There's no difference between the tanks, however the standard colors used in scuba diving are white with a black ring. When tested at the hydro facility, the tanks get a 5-year stamp according to the country's law on pressure containers. But....paint the tank in grey/green and it becomes a technical gas, and then the tank gets a 1-year hydro stamp according to European law.

Attached pdf gives an overview of color codes for other gasses.

In the US my oxygen comes in green tanks and my helium comes in blue, though I believe helium tank color can change. I wish there was a worldwide standard. It would make life easier

 

[rob.mwpropane]

Someone recently sent me a picture with a bottle connected to their nitrox stick. It was RED, I was like wtf is that!!?? Turns out Canada O2 is red...who knew.

 

[Miyaru]

In the US my oxygen comes in green tanks and my helium comes in blue, though I believe helium tank color can change. I wish there was a worldwide standard. It would make life easier

I just re-read my post and saw I forgot to add the word not. Makes a big difference! Post edited....
So to be complete: color coding is not the same worldwide, not even within the same country!