Revisiting an old topic: Welding O2?

[gxsr_sarge]

Greetings all: I checked and it seems as though this topic hasn't been covered in this sub-forum since mid-2007 (http://www.scubaboard.com/forums/co...systems/194802-welding-versus-medical-o2.html) so I figured I could revive the topic.

I'm in the final stages of setting up my new home PP blending system and am now trying to secure O2 and He. I thought that I had secured "Tech Diving Grade" O2 w/ Praxair after having sent in my application showing my c-cards for both blending EAN and Trimix gases and also for using them. They just gave me the Heisman and told me that since I wasn't a "certified retail dive center" (whatever that means), I couldn't buy from them . So I'm looking at industrial/welding or "aviator" grade O2.

I don't think I'll have a hard time buying welding O2. I just called Praxair's "front desk" and asked them what buying O2 entailed. They immediately asked "what for" - I said, "Oh, for oxyacetylene welding". The guy immediately said to just swing by, lease a tank and you're set.

I've asked a few suppliers before about Medical O2 and they said no-way b/c you need a prescription. So that leaves Aviators as far as the other "breathable gas".

My questions (please consider any or all) are as follows:

- What response would I give for the inevitable "why do you need aviator's grade O2 for"?
- Is there a valid "welding or torch cutting" reason to ask for a purer, dryer or cleaner form of O2?
- What are your experiences in dealing w/ suppliers in buying O2 or He? Do you tell them what it's for?
- Lastly, HAS ANYONE EVER HEARD OF ANYONE BEING HARMED FROM BREATHING "WELDING" GRADE O2? I know that many may prefer to buy Medical or Aviators just to feel cozy - but really, does it matter?

Cheers

 

[steamtrollnuke]

From what I remember from the Navy Nuclear Emergency welder class I took,
Technical 02 (welding) is at least 99.8% pure. solid green bottle
Medical 02 is at least 99.9% pure, white top half
Aviator 02 is at least 99.9% pure and actually has a lower moisture content than Medical 02, white band

We used Aviator grade 02 for the entire welding class, I don't see why you should have to give a reason why you want aviator grade 02.

 

[gxsr_sarge]

Does "purer" = "more breathable"?

For example, Matheson Tri-Gas categorizes their O2 as follows:

Research Purity, 99.998% (< 5ppm Argon, 0.1ppm CO2, 0.1 CO)
Matheson Purity, 99.997% (< 15ppm Argon, 1ppm CO2, 1ppm CO)
Ultra High Purity, 99.98% (< 1ppm CO2, 1ppm CO - no argon listed)
Zero Gas, 99.8% (doesn't list tolerances)
Extra Dry, 99.6% (doesn't list tolerances)

They all indicate "not for human consumption". I couldn't find anything that listed "aviator".

I'm guessing that Research Purity is best though they don't offer 337 Cubic Ft sized cylinders. The middle three above are the only ones that come in 337's (1L's).

 

[pescador775]

I see no need to revisit this topic or define "pure" beyond what is obvious lest it become an Abbot and Costello act, "Who's on First?" Here is some reading material. BTW, I use welding oxygen.

Applications Detail

 

[gxsr_sarge]

I see no need to revisit this topic or define "pure" beyond what is obvious lest it become an Abbot and Costello act, "Who's on First?" Here is some reading material. BTW, I use welding oxygen.

Applications Detail

pescador775, I don't mind (and welcome) the Abbot & Costello act. I'm here to acquire knowledge from folks like you on how and where they buy gases (along with the "tactics" ). Something could have changed since 2007 - I don't know. I suppose that with over 2600 posts, you've seen it all but I'm still a relative "newbie" both to the forum and the blending. So please .....

 

[pescador775]

There is no change. Local gas suppiers are independant actors. Individually, they set rules, sell to whom and at what price they choose. They appear to hold to the view that they are "pros" and everybody else is a sucker or a potential hazard or lawsuit waiting to happen. They misinterpret rules for perscription drugs and other things or make up their own. Buy some aviator's oxygen and tell them it is for industrial use. However, any differences with welders oxygen might be hard to prove. Any inert gas such as nitrogen or argon is a potential contaminant but the kick back would be from welders as opposed to divers. Before filling, the supplier is supposed to draw a vacuum on the tank before transfilling pure, cryo oxygen. The are probably conscientious about this because if a flammable substance were present in the tank they would be first to hear about it (booooom)..

 

[Thalassamania]

It is my understanding that the only actual difference between welding oxygen and medical oxygen is that at the final delivery point the suck a vacuum on the bottle before filling it with medical oxygen. Same product, same cooling tower ... different delivery protocol.

 

[cool_hardware52]

It is my understanding that the only actual difference between welding oxygen and medical oxygen is that at the final delivery point the suck a vacuum on the bottle before filling it with medical oxygen. Same product, same cooling tower ... different delivery protocol.

Would you introduce High pressure Pure O2 into any commercial cylinder of of unknown provenance, particularly if this cylinder is at or near empty?

I wouldn't and my local gas supplier won't either.

Tobin

 

[Thalassamania]

I would not, but evidently it is done with welding oxygen cylinders thousands of times every day.

 

[Gilldiver]

Having been at all of the major gas manufacturers and re-packagers for a major aerospace corp doing a corporate purchasing agreement, I found that there is no, that means zero, difference between how tanks are handled until you get above UHP levels. That means 5.0 grade or 99.9990%.

All the pure gas comes from a liquid source, welding tanks, etc get vacuumed and refilled in batches of up to 12. Once the batch is filled in about 5 minutes, the operator checks his computer screen and the screen tells him what is need at that instance. If anything other then welding gas is required, a bottle from the batch of 12 is tested and the stickers are printed out and the bar codes on the tank are recorded. So from that batch of 12 tanks, 6 may be welding, 2 Aviators, and the rest UHP.

Aluminum medical tanks are treated slightly different if they are aluminum or smaller then the 200 or 300 cubic foot tanks.

So, the difference between welding O2 and He and UHP O2 and He is a piece of paper, nothing more. But if you sell that gas or give it to anyone else, that piece of paper can be very valuable if you get sued.

Now when you get above 5.0 (99.9990%) the bottles are treated differently. They will be heated to above 212F to dry out any water, flushed and vacuumed at least twice, filled and may be individually tested and cost a lot more then any diver will ever want to pay.

Last, the major gas plants are set up to fill over 10,000 bottles per year. Just how much care do you think they can give to each one? Also, the fill stations are all on what looks a lot like a unheated loading dock.