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There are other costs:Quote:
Originally Posted by JahJahwarrior
- Throwing away gas every time a supply cylinder goes below 500 or so and you can't use it in the cascade. You lose about 25% of each tank.
- Time. It takes a lot more hands-on to be using a cascade
- Cost of multiple cylinders and connection ahrdware for the cascade
- Lost busienss for people who go elsewhere for an O2 fill... AND all their other business.
You can get 2nd hand AG30's sometimes for around $1500. Watch ebay.
when it comes to HP O2, I am old school Navy, and only use steel cylinders, i.e. 45s or 72s. Twenty years ago, you never saw anyone putting 100% O2 in an aluminum cylinder. It has become more common place today and even the medical industry uses small aluminum cylinders for personal/portable O2 delivery systems. I still like the steel because it affords some negative buoyancy at shallow deco depths if required. Plus, if it is a LP cylinder, you are close to a complete fill (rated volume) at 2400psi.
If your nitrox fill system is the kind that puts o2 into a mixing stick and connects that to your compressor input, you can use low o2 cascade tanks to fill nitrox with, which lets you use the bottles down to, what, 14 psi?Quote:
Originally Posted by aainslie
Cascades do take time to use, but so does running a Haskel. I'm not sure exactly how much time each takes, so you might be right, I just don't know how much of an issue this is.
As far as cascade hardware goes, in reality, you'd be pumping your supplier's bottles into your o2 bank, most likely. Then, you'd cascade fill off of these. So, with or without a booster, you'll likely have to purchase some cascade hardware. This is a tradeoff of time: you can run a cascade with a single o2 whip, moving it from bottle to bottle as needed using more time, or you can purchase hardware and use less time, depending on what is more cost effective.
How many shops have boosters? There might be one shop within an hour of me that has one, and I'd rather go to the closer shop and get a 2400psi fill than drive an hour for a 3k fill. If your competition has boosters, then you might want to consider it. If they don't have boosters, it might not be hurting you much to not have one. You could always compete on other things--a lower price on o2 per cu.ft will bring in plenty of people who'd rather save money on the cu.ft. even with the lower final fill pressure, I think. I could very well be wrong, it's hard to do market analysis over a forum.
I am one of many who is happy to receive a 2000 psi O2 fill, and thrilled when I get 2200-2400. A 3000 fill of O2 actually makes me a little nervous, and I don't want it unless I'm going to use that first few hundred psi on a dive in the next couple weeks. I am, however, one of those mentioned above who has a LP 45 for my O2 deco bottles. This is for the lower pressure rating, but more so for the excellent buoyancy characteristics as a deco bottle.
Slightly off-topic, but my O2 (and EAN 50) bottles always either have a SS DIN plug in them or a reg attached to prevent any unintentional unleashing of a high pressure stream of combustible gas.
WJH
WJH, neither the O2 or 50/50 is combustible. A better term is accellerant. High pressure, fast moving O2 makes things that would ordinarily not burn go up in flames. Examples of this are tank valves, O-rings, brass and SS fittings, hoses, and even Haskell heads. Impingement is another problem. A small particle is moving with the gas and hits something else, or the friction causes it to get hot and eventually burn in a rich O2 environment. Thus the basic rules for O2 filling. Go slow, stay below 3000 p.s.i., use a filter on your cascade manifold, keep things cool.
Just a FYI. Having been standing 8 feet Away when an O2 bottle exploded. The US Navy does not fill oxygen more than 3000 psi for safety reasons. I don't fill mine more than 2800. Safe diving. Ken
This is one of those shaving of terms that is misleading, a difference without meaning. The "combustible" stuff won't burn without oxygen, and the oxygen won't burn without the "combustible" stuff. Who cares about the label? Oxygen's dangerous; pure oxygen will make things burn merrily that we normally don't think of as flammable at all. If you aren't a little nervous when transfilling oxygen, and more than a little nervous when boosting it, it can only be because you've never witnessed an oxygen fire first-hand.Quote:
Originally Posted by fno
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I will boost oxygen to 3000 psi in an AL40, but not one psi more :)
(we use a two stage Haskel, and meter the boosting gas very carefully to keep rates nice and slow)
Rick
Gregg Stanton pointed out something to me that's jsut as important - the CHANGE in pressure. His rule is, don't boost more than 3x supply. It's a good rule, to stop overheating on the Haskel.
We don't lose that 25%. I drain it to about 10% filling empty al80's (O2 clean of course), then top them off with O2 and dive them as travel mix based on whatever I squeezed out, or sometimes just use it as nitrox and ignore the little helium (safety factor).Quote:
Originally Posted by aainslie
We also take the last bit and fill balloons. My stepdaughter and I have a good time filling them, putting them in the back of the pickup with a cover and then launching them en masse!
We've even begun to glue together mylar sheets for a really big balloon ... did you read about those guys and gals at MIT who launched a helium balloon to the edge of space with a cell phone attached taking pictures? It even got the pic of the helium balloon popping due to pressure differential in space! The earth pictures are amazing too. all for less than a hundred bucks.
Soon my stepdaughter and I will be launching a balloon into space with that left over helium! I hope to watch it from the backyard telescope. With more mylar layers it could stay aloft at the edge of space longer than with fewer mylar layers...right?
PS: don't tell NASA.
-skip
Hey Skip, glad to see a post from you - we know you are alive. We missed you on Sunday.Quote:
Originally Posted by skip