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Author: Subject: Gas bottle threads
alistairolsen

posted on 4/4/11 at 03:21 PM Reply With Quote
Gas bottle threads

Can anyone tell me what threads are commonly used on argon bottles (5 foot ones if it matters) from BOC and Air Products? Also, what threads are used on pub gas bottles? I mean the outside of the valve, where one would normally screw in the regulator?

Cheers





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Andy W

posted on 4/4/11 at 04:46 PM Reply With Quote
5/8" bsp, they are both the same, I had a pipe made up to be able fill my pub co2 bottle from a full size argon.

Andy

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Peteff

posted on 4/4/11 at 05:27 PM Reply With Quote
quote:
Originally posted by Andy W
5/8" bsp, they are both the same, I had a pipe made up to be able fill my pub co2 bottle from a full size argon.

Andy


Pub co2 is a liquid and Argon is a gas under high pressure so the pub gas cylinders are totally different ratings and not tested for the higher pressure. It would be safer to get a proper Argon or Argon/co2 mix cylinder for the job.





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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cryoman1965

posted on 4/4/11 at 06:01 PM Reply With Quote
quote:
Originally posted by Andy W
5/8" bsp, they are both the same, I had a pipe made up to be able fill my pub co2 bottle from a full size argon.

Andy


STOP They are NOT the same. CO 2 is charged in a cylinder at 50 bar. Argon is filled at 200 - 300BAR depending on the spec of the cylinder. Clearly the cylinders are tested to differing pressures. DO NOT do this. The fittings are also different, one is male and one female. This is to stop numpties connecting to the wrong cylinder.

All friendly advice.

HTH

Nige

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alistairolsen

posted on 5/4/11 at 07:34 AM Reply With Quote
The way I view it is that the argon supply for the welder is regulated down to about 10psi ish, so the pressure in the bottle only relates to the time for which your bottle lasts.

The large argon bottle has a valve in it which you can shut off easily if you burst a pipe.

My intention was to gauge the bottle I'm filling, and bring it up to working pressure gently, Probably using something like 5mm nitrous line (plastic, rated to 1500psi) so if it bursts I don't get metal flying around. Even if I only get 900-1000psi instead of 3000, it just means I have to fill it more often, but still a LOT less often than those stupid disposable bottles.

A friend has a fabrication business and uses argoshield regularly, dad and I will soon have separate garages and welders, so some connection for filling would be great.

Best I have found so far (and looking for a locost solution to do the same) http://www.noswizard.com/product_desc.php?id=184 Thats from an industrial gas cylinder down to a hmm nitrous line and olive. If I use a CO2 fire extinguisher then I need to get back up to 22mm.

So, anyone know where to find male 5/8 cone seal brass reducers?





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Peteff

posted on 5/4/11 at 03:42 PM Reply With Quote
quote:
Originally posted by alistairolsen
The way I view it is that the argon supply for the welder is regulated down to about 10psi ish, so the pressure in the bottle only relates to the time for which your bottle lasts.

The large argon bottle has a valve in it which you can shut off easily if you burst a pipe.

My intention was to gauge the bottle I'm filling, and bring it up to working pressure gently, Probably using something like 5mm nitrous line (plastic, rated to 1500psi) so if it bursts I don't get metal flying around. Even if I only get 900-1000psi instead of 3000, it just means I have to fill it more often, but still a LOT less often than those stupid disposable bottles.


If the co2 cylinder is rated at 50 bar it is approximately 750psi so filling it from any high pressure gas cylinder is going to exceed it's designed rating. If the cylinder bursts or the valve exits the cylinder you will still have metal flying round, it's not the pipe after the regulator running at 10lpm where the problem will be. You can buy a proper tested argon/co2 mix cylinder from several places nowadays then refill it yourself if you want but the co2 cylinder is not the thing for the job. Co2 is a liquid fill not a gas under pressure and what you are suggesting is dangerous, the actual cylinder could become a grenade. I'm not usually bothered by safety issues but what you and Andy are suggesting actually scares me. I went on a welding course many years ago and the videos they showed on cylinder safety gave me a health respect for pressure vessels.





yours, Pete

I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.

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MikeCapon

posted on 5/4/11 at 04:12 PM Reply With Quote
I know very little about gas bottles and the like, apart from the fact that they scare me witless. Hundreds or even tens of bar are bombs waiting to go off.

A sobering tale. This happened to a colleague of mine over here. He was fitting a tyre to a trailer wheel in our old workshop. To seat the tyre he blew it up with the airline. We don't know how many bar he put in and neither does he.

The wheel was poorly welded and blew apart taking a good part of the top of his head off. He survived due to excellent and rapid medical attention but he was completely blinded in the accident and his face was horribly disfigured. He subsequently lost his wife, his business and his marbles.

The airline in the workshop was limited to 8 bar and you are talking about 50 bar like it was small beer.......

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alistairolsen

posted on 5/4/11 at 04:53 PM Reply With Quote
quote:
Originally posted by Peteff
quote:
Originally posted by alistairolsen
The way I view it is that the argon supply for the welder is regulated down to about 10psi ish, so the pressure in the bottle only relates to the time for which your bottle lasts.

The large argon bottle has a valve in it which you can shut off easily if you burst a pipe.

My intention was to gauge the bottle I'm filling, and bring it up to working pressure gently, Probably using something like 5mm nitrous line (plastic, rated to 1500psi) so if it bursts I don't get metal flying around. Even if I only get 900-1000psi instead of 3000, it just means I have to fill it more often, but still a LOT less often than those stupid disposable bottles.


If the co2 cylinder is rated at 50 bar it is approximately 750psi so filling it from any high pressure gas cylinder is going to exceed it's designed rating. If the cylinder bursts or the valve exits the cylinder you will still have metal flying round, it's not the pipe after the regulator running at 10lpm where the problem will be. You can buy a proper tested argon/co2 mix cylinder from several places nowadays then refill it yourself if you want but the co2 cylinder is not the thing for the job. Co2 is a liquid fill not a gas under pressure and what you are suggesting is dangerous, the actual cylinder could become a grenade. I'm not usually bothered by safety issues but what you and Andy are suggesting actually scares me. I went on a welding course many years ago and the videos they showed on cylinder safety gave me a health respect for pressure vessels.


I don't wish to do anything dangerous. Filling a bottle is no different to filling a tyre. You fill a tyre to 30psi from an air receiver at 100psi through a pipe. I want to fill A.N.Other bottle to no more than its safe working pressure from a high pressure receiver full of argon. As long as flow is limited and pressure monitored so that the valve is shut before the safe working pressure of the recipient bottle is exceeded then I don't see an issue? I understand of course that if I just whack the valve on the argon bottom open I will equalise the pressure between the two bottles and most likely blow myself and the entire garage into next week.

CO2 is only a liquid because it is stored under pressure. as far as I understand its behaviour in a pressure vessel is the same in that it exerts an even outward pressure on every internal surface. Its change in state from a gas to a liquid of course means you can have a far greater volume for less pressure (and hence the bottles are normally smaller) but as long as the bottle safe working pressure is not exceeded again, I don't see a problem?

I'm not trying to put 225bar in a CO2 bottle, Im not trying to put 1/3 of a large cylinder into one which is 1/3 of the size, I'm trying to fill a cylinder of a reasonable volume to its safe working pressure and nothing more. I don't care if I have to fill it once a month where a proper cylinder would last 3-4 times longer as the pressure is higher!

If I've genuinely missed some glaring technical issue then please tell me, I'm not a wild risk taker, but I genuinely cant see a problem in principal.

The reason for the nitrous line is to limit the flow rate and also because if a plastic line fails goggles will help. If a steel gas pipe fails its like a grenade.





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