Heliiox Through Compressor

Marc T

does someone have serious information about the maxi O2 level you can safely use in a compressor when the diluent is hélium?

Etherybody know its 40% with nitrogen

With héliox I often use 15% and 20 % without problem and one time 36%
Do you think its dangerous and why?

Beanie

depends on the compressor anything up to 21%HeO2 should be fine for obvious reasons above that it would be the same for nitrox surely but it has to depend on the compressor and what its rated to / manufactures recommendations

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jradomski

First everyone doesnt know its 40% nitrogen.. I have pictures of more than 1 compressor blowing up pumping less than 40% through it.. some were as low as 32%

The big thing with pumping helium through a compressor is that it gets REAL hot.. the final stages will get much hotter than usual, if you raise the oxygen content as well you are dramaticlly increasing the chances of a BOOM...

Keep the o2 down and if possible slow the compressor down (change the ratio of the drive to the compressor or a slower motor).

attached is a phot of a compressor that blew up pumping less than 40%

Attached Images

compfire2.jpg (115.8 KB, 221 views)

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decoweenie

I have been pumping trimix thru my own compressor for the last 5 years. Most of the time, it is left-over 10/50 but on occasion 10/70. When the Helium tank is low, I pump pure Helium thru the compressor as well. A friend pumps Helium thru his compressor for hours with no issue. Back during OC days, it was a mixture of different hypoxic trimix since I have no need for normoxic trimix much less high O2% heliox.I have known friends pumping Nitrox thru their own compressor, but can't recall the exact fO2 so don't want to pass out the wrong info.

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Barrie Law

Mark,
The fraction of O2 you can put through a compressor depends on the compressor and the operator, especially how well maintained the compressor is, O2 is fairly predictable up to 40% pumped to 230 Bar above 40% and 230 Bar things become less predictable.
There is no reason for not pumping bottom mix Heliox through a compressor as this normally has a low O2% but if pumping bailout Heliox eg 50/50 you have to be cautious.
Helium by it's nature will as Joe said cause the compressor to run hotter but it will also find it's way passed the piston and into the crank at the same time "washing" the lubricant as it passes, this can be roughly calculated by putting a known bottom mix through the compressor and checking the helium % after compression.
A good quality well maintained compressor will lose a few % of Helium in the process, a Nitrox compressor will loose less and should have a feed back from the crankcase to the first stage.The danger is when mixing bailout Heliox eg 50/50 the compressor is hotter and the lubrication is diminished by the passing Helium so caution is required.
Now if you pump rich Nitrox immediately after pumping Heliox you could have a major problem even with much less than 40% O2, letting the compressor run for a while between different types of filling will help but again the mix's being pumped and the compressor are variables that have to be considered by the operator.

Cheers

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MikeH

I have run pure helium, 10/70, 15/50, 18/45, 32/30, and 50/50 through a Rix for bottom mix and deco gases. I have run the same gases, minus the 50/50, through a Bauer compressor as well. None of this caused any issues.....BUT....these compressors were impeccably maintained and I knew their maintenance history. Without having known their maintenance history, I would not run anything richer than 21% oxygen through. Pure helium is not an issue as long as you monitor the temps. The compressor WILL get much hotter than if you are pumping air, and it depends on the specific model whether or not it can handle those temps or if YOU need to keep an eye on it and let it cool when it gets to a certain point.

Mike

iain-hsm

Enclosed Jpeg on helium fire at 20%

Attached Images

gas fire 1.pdf (119.6 KB, 50 views)

iain-hsm

And another fire with nitrox 36% at only 20 bar.

I would like to know if we are talking about specific designed gas compressors or just chancing it through your air compressor?

Attached Images

Nitrox Explosion0165.pdf (120.8 KB, 26 views)

Pelagian

Hey Mike

Can you explain why this is?

Cheers

Seb

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MikeH

Specific Heat Capacity of Helium is much greater than that of air....approximately 5 times as much, IIRC. This means that for a given volume, the Helium can hold about 5 times as much heat as air. Helium is also much more compressible than air due to much smaller molecules and the fact that there are many more of them(7-8 times as many) in a given volume at a constant pressure. The Helium will therefore heat up more easily during compression, and will hold much more heat. When you run a gas through a compressor, it compresses it(obviously) which causes it to heat up.

If you run Helium through a compressor, it's a good idea to have additional cooling, which could be as simple as having a portable fan blowing across the cylinders, or as elaborate as a heat sink system with cold water flowing through it. A friend of mine did the latter, but he's an engineer that loves to tinker with things like that, and spent more time/money than he would have to buy another compressor.

I do, however, know many people that run Helium through a compressor with no additional cooling with no problems. It all depends on the compressor. I, personally, use the portable fan for additional cooling, and just monitor the cylinder head temperature(with something like THIS).

Mike