Liquid O2 dewar for continuous blending?

[hawksbill]

I am wondering if liquid O2 for cont blending is worth considering for larger operations.

I am not familiar with Dewars but heard the vent pressure is 350# so I hope to be able to provide 50# pressure to my regulator. My compressor is max of 6 cfm so maybe 1.3 cfm draw of O2. May be blending as much as 2000 ft3 of 40% nitrox per week.


Any advice, considerations, experience or concerns welcome. Thanks Robert

 

[Blue Abyss]

Mike Leaver who runs the Nautilus Explorer uses liquid oxygen to feed his nitrox sticks.
Using liquid oxygen should work just fine as long as you have a regulator setup that you can control the flow to your stick. The only down side to LOX is that you loose some due to evaporation but if you are going through if fast enough it is a cheaper way to go.

BB

 

[Gilldiver]

Mike Leaver who runs the Nautilus Explorer uses liquid oxygen to feed his nitrox sticks.
Using liquid oxygen should work just fine as long as you have a regulator setup that you can control the flow to your stick. The only down side to LOX is that you loose some due to evaporation but if you are going through if fast enough it is a cheaper way to go.

BB

Depending on the type of dewer and your ambiant temp the evaporation loss amount could be as high as 10% per week. But for SCUBA, a dewer is a lot of gas, will you use it? The only places I know of that pump enough Nitrox are in Florida unless you are doing a commerical Heli-Ox system. Even those guys use compressed most of the time.

Include a gassification system between the dewer and the stick that warms the gas up to close to ambiant or you will run the risk of freezing the stick.

 

[rjack321]

Ambient temp in SE Alaska is not very high, but I suspected the dewar would probably get barged in from Seattle (even Anchorage doesn't have a gas plant I'm told).

4000cf of 40% is not really that much and I suspect use is mostly seasonal as well. Compressed is probably a better deal, at least it keeps indefinitely.

 

[hawksbill]

Thanks for the info so far, I heard of some local guys doing torch work on glass using lox because for us in Alaska, shipping is the big expense. 4000 cf of compressed O2 in 17 welding bottles is about 1200 dollars and the equiv LOX in the dewar I heard is about $400 including rental of the dewar for 40 days. At this point it may not be worth the hassle of the LOX off-gassing, the rental, or any other hassles to save a few hundred bucks.

Any other input on this by those who know is appreciated.

 

[dannobee]

Wow, shipping's expensive up there.

Have you looked into a membrane or PSA system instead? It'd be more expensive initially, but if you're paying that much to ship O2, it'll pay for itself quicker than down here.

 

[hawksbill]

To give a clear picture, the prices I gave are for gas with shipping. $75 for 250ft3 bottle of O2 welding. Or, as I was told, $400 total for 17 bottles worth (4000cft) of LOX in a dewar for 40 days. I guess some people pay less than $30 for a 250cft O2 bottle. Anyway the point of this post was to find out the practical realities of using LOX for cont blending since I have no experience with LOX and have seen no mention of using it in what I've read.

 

[hawksbill]

I decided on blending over a membrane system based on the ititial cost, portability, trouble and long payback time. Dont know about PSA for expense and time to break even compared to bottled gas. 5-10 years to pay for itself may be too long. So far I have only spent about $500 for O2 gas for 1 year. I am just checking out the options and trying to keep things simple.

 

[rjack321]

The only setup I've ever seen is Mike Lever' on the Nautilus Explorer. Its pretty simple stuff - no more complicated than a gas bottle and welding reg.

Maybe your dealer can give you some info on expected loss rates.

Thanks for the info so far, I heard of some local guys doing torch work on glass using lox because for us in Alaska, shipping is the big expense. 4000 cf of compressed O2 in 17 welding bottles is about 1200 dollars and the equiv LOX in the dewar I heard is about $400 including rental of the dewar for 40 days. At this point it may not be worth the hassle of the LOX off-gassing, the rental, or any other hassles to save a few hundred bucks.

Any other input on this by those who know is appreciated.