Welding versus Medical O2?

[Jimmer]

Thanks for the tip Steve, I'll give BOC a call anyway for the sake of pricing, plus I'm told they do T bottles whereas Praxair only handles K's, and since neither myself nor my shop have a booster, we figure having 2 or 3 T's in a mini cascade would help out a lot with getting higher pressure fills when needed.

 

[Steve R]

BOC around here, the last time I checked has no T's of helium (but yes they do of oxygen), but they'll gladly sell you a K for the price of a T......the rapists...lol.

Having no booster really sucks for waste-age. Not too bad with oxygen, but you're throwing a lot of $$$ away when it comes to helium.

2-3 bottles with no booster won't get you much of anything really, and certainly isn't suitable for more than a couple people at most when PP'n.

You really need a booster or to get into a CB at a minimum, when doing anything like this.

I'm about as small as you can get, and I find there is times when it's a full time job to keep the banks up and have the mixing getting done that needs doing.

 

[Scuba Duck]

You might consider continuous gas blending, you get all the oxygen or helium out of the tank, and when it comes to filling multiple SCUBA cylinders, its a huge time and effort saver. The Standard Nitrox Stik (continuous gas blender) can be easily adapted to make Trimix.

http://www.envirodive.com/stikinfo.php

There also exists an automated control system that really reduces the burden on the person doing the blending. Very accurate too, within .1%, much better than most people can do Partial Pressure Blending. There is a video on the website that covers many features of the controller.

http://www.rubberduckiedesigns.com/NitroxController.htm

If you are blending mixes with higher than 40% oxygen, you'll still need your partial pressure setup. But if your most common mix is 32%, continuous gas blending is certainly the way to go.

This website has a comparison of the differnt methods of making Nitrox.
http://www.nitroxmadeeasy.com/index.html

 

[Hoosier]

$2300 for a nitrox stik....... LOL~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

[rjack321]

$2300 for a nitrox stik....... LOL~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

No kidding, $150 would do it with an O2 analyzer. Nothing like a $2150 profit on some PVC pipe, wooo hoo!

 

[Hoosier]

No kidding, $150 would do it with an O2 analyzer. Nothing like a $2150 profit on some PVC pipe, wooo hoo!

How could be? That's my question...... It is very interesting market.

 

[Scuba Duck]

Here is a couple of things in mind before you balk at the price of the stik.

1) It's patented in North America, any one who sells a knock off is infringing on the patent and comitting a crime. The inventor gets royalties from each sale. Without his initial effort, none of the knock offs would exist.

2) Cascading orifices as suggested in several forums or available books is not as efficient as the the vortex mixing vains in the Nitrox Stik. A cascading orifice is essentially a muffler, mufflers cause restrictions and backpressure. That restriction will reduce the life of your compressor. If you open the size of the holes to reduce the restriction, you decrease the mixing.

3) The Nitrox stik has been tested by an independant lab to verify that it thoroughly mixes the gases while providing a mimumum of restriction. While you may feel that your knock off stick will do the trick, I very much doubt that you have any analysis to support this claim.

4) If you make something like the Nitrox Stik yourself, and blow up your compressor, you didn't save any money.

5) The Nitrox Stik probably looks a lot better than whatever cobbled together piece of PVC you have in your garage.

 

[Hoosier]

Derek,

I am sure your system must be a good...

But, our points are

1. Have ever read any posts that someone blew up their compressor due to a home made nitrox stik here and there? We don't read anything yet.

I have two home made nitrox stiks. I know so many divers who built a nitrox stick by themselves. Your argument is an "overkill"

2. Mixing is a mixing. Once it works, it works. There is no magic in my view point.
You can drive a Porsche to go to Canada, but my 10 year old sedan can be there at the same time.

3. You are a business man... So, you must know Benefit-Cost Analysis. As a customer, sorry, BC ratio is too low with your option.

4. Garage is a Garage.. Who cares interiror. It isn't my bed or living room. Do you put a chandelier in your garage?

5. What analysis? O2 sensor isn't enough for a mixing? My sensor shows 32 on my tank. What other device do I have to use to make sure of mixing...

 

[Scuba Duck]

I have seen the results of someone's ill advised and poorly contrived attempt to manufacture a home made nitrox stik. He got to replace a K15 Bauer compressor. That cost much more than the Stik would have. I'm not sure where he got the idea of how to make the stik, and no he doesn't post on Scuba Board. He owns a legitimate Nitrox Stik now and a relatively new Bauer compressor. Many people insist on learning the hard way.

Mixing is not mixing. There is a non dimensional number called a Reynolds number that characterises the stability of fluid flow. The problem with these gases is that you can't see them. If you add dye to a can of paint, how long do you have to mix it to ensure it is homogeneous? You can tell if paint is mixed by looking at it, with air and oxygen, it is not so simple. Does your stik really homogeneously mix the gases, or do you feel that it works? What engineering analysis have you done? When Dr. Morgan Wells originally came up with the idea of continuous gas blending, he blew up more than one compressor due to inadequate mixing of the gases before compresson.

I don't make the Nitrox Stik, it's made in Canada, I live in Hawaii. I designed and make the automated control system that is a companion product for the Nitrox Stik. This control system will work with your home made stik too. Much like the Ronco Showtime Rotissery BBQ, you just set it, and forget it. If you fill a lot of Nitrox, are looking for accuracy, and don't want to baby sit the system while you are filling Nitrox, the controller might be good for you. As far as cost benefit analysis, if you calculate the amount of time you spend filling Nitrox, multiply that time by a labor rate, you can determine how long it would take to recoup the cost of the system. For dive shops that fill Nitrox on any scale, the controller makes a lot of sense. It makes less sense for the home blender who fills only a couple nitrox tanks in his garage.

 

[rjack321]

Good luck enforcing that patent. Looks like its being tread on all over.

Check out http://www.mcmaster.com/ page 472 has all sorts of premade mixing sticks like this for 1/20th of your price. If you want to get anal they even have the quite simple formula to calculate a Reynolds number to confirm complete mixing.