Compressing Helium Mixtures

[Scubadude_LA]

Can't seem to find a good answer to "What percent of helium is safe to run through a compressor?"
Any input for those who actually know would be appreciated.
thanks

 

[dannobee]

I dunno about "safe," but I've run 55% through my Bauer. It does make a higher pitch sound when you turn on the gas, but other than that, I haven't noticed much difference, including temperatures.

 

[Wookie]

Aside from the losses, I can’t imagine there is anything unsafe about compressing helium. If you can afford to compress it and suffer the expense, go for it.

 

[tbone1004]

a lot of compressors will have head temperatures shoot through the roof with helium so make sure you have an IR thermometer and are keeping track of that. That said I don't know why you'd want to be compressing it, much easier to PP blend with helium especially if you want any sort of an accurate mix

 

[RayfromTX]

How would you PP blend without a booster? The options are all costly.

 

[tbone1004]

How would you PP blend without a booster? The options are all costly.

helium comes at a pretty high pressure out of the bottle so you can usually blend it to somewhat decent mixes without a booster. Putting 10-20% through the compressor probably wouldn't hurt it but I'd be real concerned about trying to run say 21/35 through the compressors

 

[Akimbo]

Heat is an issue with high Helium percentages. We pumped tube-trailer quantities of pure Helium and HeO2 with less than 6% Oxygen on saturation diving systems. The best compressors we found for continuous duty had water cooled interstage heat exchangers. You can just monitor head temperatures for the small quantities recreational and rebreather divers would use. Add a big fan and stop pumping for a while if necessary. A non-contact Infrared temperature gun would be a good investment.

 

[RayfromTX]

helium comes at a pretty high pressure out of the bottle so you can usually blend it to somewhat decent mixes without a booster. Putting 10-20% through the compressor probably wouldn't hurt it but I'd be real concerned about trying to run say 21/35 through the compressors

Assume you are turning at thirds and surfacing with ~1000 psi. You either dump that mix so you can pp blend the helium down to say 500 in your helium supply tank and only return 25% of that supply cylinder unused which means waste a third of your dive cylinder and 1/4 of your supply tank.

Or you an blend on top of the partial dive tank and end up using around half of you helium supply cylinder before you are down to the pressure in your dive cylinders. The helium cylinders only come with around 2000 psi from most suppliers I am familiar with.

I know that this is old news to you Tom but I'm stating it here for those that are just getting started.

 

[Vicko]

Assume you are turning at thirds and surfacing with ~1000 psi. You either dump that mix so you can pp blend the helium down to say 500 in your helium supply tank and only return 25% of that supply cylinder unused which means waste a third of your dive cylinder and 1/4 of your supply tank.

Or you an blend on top of the partial dive tank and end up using around half of you helium supply cylinder before you are down to the pressure in your dive cylinders. The helium cylinders only come with around 2000 psi from most suppliers I am familiar with.

I know that this is old news to you Tom but I'm stating it here for those that are just getting started.

How common is that, here I can get 250/300 bar T bottles from any welding supply store.
On the other hand I just got a Draeger U300DS so I don't have to worry about it any more

 

[iain/hsm]

On the other hand I just got a Draeger U300DS so I don't have to worry about it any more

Really? Just have a service head kit to hand and a twin pack of seal kits on the side and know how to use them.
Again and again and again so much so after a while it will become second nature. That or just use it for pure oxygen.