blending nitrox

[350xfire]

You know, I thought about this a bit further, and if you start with a nearly empty tank, you'll be able to fill a bunch more.... My original thought was to only be able to use 1000 psi, but only assuming that you get a cylinder filled to 4000 psi, whixh, you guys are right. Don't thinkO2 is filled that high.

 

[coldsmoke]

Well if I start with an empty Alum 80 and a full O2 tank ( yes these are the standard type/size and look like a welding bottle). The top off program on V-planner says I need like 400 psi then top off with air. I guess the better question would be how many times can I get 400psi in an alum 80 from the o2 tank before the pressure gets below 400psi in the big tank? I'm pretty sure they are 250cf at 2150 psi.

Umm, it's been answered twice so far, but here it is again: You will get about 18 fills into an empty Al80

Hunter

 

[fppf]

Most industrial cylinders are 2400 PSI with a + rating to 2640.
You can get the odd ball 4500 PSI cylinder, but those are few and far between.
You can also get 6000 PSI cylinders, but hold onto your butt when they quote you the price.

 

[NAM001]

if cascading from an o2 tank (it says 2015 and is about five feet tall, i don't know the cf), about how many alum 80's can you get 30% blend after you top off with air?

Before everyone says i'm gonna blow myself up, i'm just running some numbers! I'm just curious, and have no intention of doing partial pressure blending without proper training!

ok it is perhaps a 300 cuft tank. Each mix assuming an mt al80 will need about 9-9.5 cu ft of o2 that is 350# of al80 presure. You can mix till the o2 tank gets to 350# the last fill starts at 430# of o2 tank presure the o2 tank because of 4:1 300:80 volumn difference will loose about 80-100 per mix soo 2150-350 is about 1800# and at 80-100 per mix that will be 16-20 30% mixes in al80 tanks. IF YOURO2 TANK IS 200 FT^2B THEN YOU WILL GET 2/3 AS MANY MIXES. OH YAH IF YOU ALREADY HAVE 500# WHEN YOU START OF 30% YOU WILL GET PERHAPS 20% MORE FILLS.

No you wont blow your self up. Hope this helps

 

[oxyhacker]

The 15-to-20 number in the OXY HACKER doesn't mention anything about a booster, and is just an approximation, since the exact number will depend on the size of the tank being filled and how full it already is. For priming completely drained 80's with 400 psi O2 from a full 2015/250 supply tank you should get about 20 charges before the supply tank pressure drops too low too deliver a full charge. But that number really doesn't have much to do with how many charges you will get in real life since you will be usually topping off old mixes with varying amounts of gas left as long as there is still enough pressure in the supply bottle to do so, then draining the tanks down more and more as your supply pressure gets lower, in order to take full advantage of what's left in the tank. So in real life I usually get more like 25 tanks per tank of O2 (and I am usually doing larger tanks than 80s). Partial fills are where a lot of the savings from DIY nitrox mixing come from since they take less O2, but if you were to take the tank to a shop for a top up you usually end up paying for a full fill.

Also, when I am mixing from a single supply bottle, when it gets too low to get a full charge out of I generally prime any empty tanks I have kicking around, to however high I can get them with what's left in the tank, then prime them the rest of the way when I get the new bottle. So the tank typically goes back with only 200 psi/25cf or so left in it, which is to say, about $1 worth of gas.

So you really don't need a booster, and the extra expense and complexity of using one is probably more trouble than its worth, especially considering how cheap O2 is, at least, not until you start using helium. A compressor would be a much better buy until then, since then you can use continuous mixing and suck your supply tanks completely dry!

 

[WD8CDH]

Most industrial cylinders are 2400 PSI with a + rating to 2640.
You can get the odd ball 4500 PSI cylinder, but those are few and far between.
You can also get 6000 PSI cylinders, but hold onto your butt when they quote you the price.

True, they may be 2400+ tanks, but most gas suppliers still only will fill it to 2015psi since they bank fill.

 

[fppf]

True, they may be 2400+ tanks, but most gas suppliers still only will fill it to 2015psi since they bank fill.

I have never had a cylinder under 2600.
And if I do I will take it back because I PAY for 300 some odd CF of gas, I better get it.

I only mix with one "T" bottle and I normally fill 4-6 scuba cylinders at a time. I can get the O2 cylinder down to 100 PSI or less in the middle of a run then swap it out. Or I can pickup a second cylinder and take back the empty one later, they just ding me for rental on 2 cylinders while I have them.

 

[oxyhacker]

I think this may be a regional thing. My supplier's tanks are all 2015 psi. And no pluses. Tank capacity is rated at 277 in their literature, but if you ask at the counter they will tell you "about" or "at least" 250cf. They seem to feel that O2 is cheap enough that only a piker would make a fuss about a few CF.

I have never had a cylinder under 2600.
And if I do I will take it back because I PAY for 300 some odd CF of gas, I better get it.

 

[fppf]

Well when they start charging me 20% less they can give me 20% less gas.

I see people complain all the time at the dive shop over 200 PSI in an AL 80. You bet I'm going to complain about 600 PSI in a T cylinder.