Nitrox in doubles ?

[RJP]

I guess I'm lucky then, my LDS banks 28%, 32%, 36% and 50%. The moral to this story is it depends how they are planning on filling your tanks.

Or unlucky, if you wanted to get a different mix than one of those four.

 

[Doc Harry]

If you plan to go down the tech route, it is worthwhile learning to clean your cylinders and manifold yourself. Although Nitrox was derived from rocket science, oxygen-cleaning is not rocket science, anyone can do it. But it does require some training, an ultrasoninc cleaner, a valve removal tool, christo-lube, viton o-rings, distilled water and some Joy dishwashing liquid.

In a couple of hours you can have your cylinders/manifold oxygen clean and ready for inspection.

 

[Tigerman]

To me the obvious answer seems to be "yes, the doubles should be used for nitrox". The ammount of gas you get in there will be far beyond what you need to go into deco on air and thus youd have loads of gas left in the tanks by the time you get out of the water.
Of course running out of gas would be worse than having loads left and you could always consider two dives on the same set of doubles though..

 

[Web Monkey]

If you plan to go down the tech route, it is worthwhile learning to clean your cylinders and manifold yourself. Although Nitrox was derived from rocket science, oxygen-cleaning is not rocket science, anyone can do it. But it does require some training, an ultrasoninc cleaner, a valve removal tool, christo-lube, viton o-rings, distilled water and some Joy dishwashing liquid.

In a couple of hours you can have your cylinders/manifold oxygen clean and ready for inspection.

The catch is that the guy doing the fills has to trust your O2 cleaning skills, or you're not getting any Nitrox . . .

Terry

 

[halocline]

I second that - all of the LDS I've seen in TX use partial pressure fills.

Well, you learn something new everyday. I just assumed that since I've seen banked 32% and membrane systems, and my LDS is nothing special, that it was the standard. In this case, maybe it's better for the OP to go for the O2 cleaning.

 

[rstofer]

First thing is to make sure they use the right bands for the tanks. You need 7" or 6.9" bands (good luck finding 6.9") or they won't fit.

6.9" bands are EASY to find: Reproduction Bands by Rick Green [DHP-RBRG] - $79.95 : Vintage Double Hose!, Your online source for all things related to vintage diving

I bought a pair to double up some Al 50s, just for giggles.

Around here all Nitrox fills are partial pressure blended.

Since a viz is only $7, the extra for O2 cleaning the tanks can't amount to much. The valve work is the most complex and it might run to $35 or so, each. My doubles manifold has a center outlet with valve and a right post valve with outlet so there are two valves to service. But it only needs to be done once as long as you always use Grade E air.

Richard

 

[TSandM]

With regards to your concern that Nitrox will limit your depth -- You always have the option of filling the tanks with a mix appropriate to the depth you intend to reach. But as pointed out, you will get much more bottom time in the 100 foot range with Nitrox, and bottom time is what we're all after, right?

Although my LDS banks 32%, the demand for it is so high that they end up doing some PP fills anyway. My philosophy is that the guy in the shop who is doing the filling is the one who is taking the risks -- I'm not going to have an O2 fire in my house. So I let them do what they feel they need to do to be safe filling my tanks, and that way, when I run in one afternoon in desperate need of a quick fill for a spur-of-the-moment dive and their banks are empty, I get a Nitrox fill while I wait, and everybody's happy.

I guess what I'm trying to say is that if you have the tanks O2 cleaned, you have lots of options; if you don't, you lose some of them. And although this sounds snippy and sour, if the cost of having the tanks O2 cleaned is a deal-breaker, then technical diving may not even be an option for you.

 

[dl348]

Or unlucky, if you wanted to get a different mix than one of those four.

I'm sure he can get another percentage mix than those 4 that he mentioned, it may take a little longer though.

 

[Slonda828]

Or unlucky, if you wanted to get a different mix than one of those four.

I agree. We partial pressure blend so guys can get best mixes. Try that with banked nitrox. Additionally, if your shop uses OCA (oxygen compatible air) then you can be reasonably assured (note I said reasonably) that your oxygen clean cylinders will stay that way for practical purposes. The company that tests our air uses IANTD OCA standards which makes the regular air with which we fill tanks as clean as the nitrox. This means that clean tanks stay clean. FWIW every shop down here in GA uses partial pressure filling, even the larger ones. If it were me, I would double the 72's and ozygen clean them. Throw some of the oxygen hacker's nitrox stickers on them to be cheeky, and use them for all your air and nitrox diving. Just make sure to ask if a shop has OCA or "safe air" when you get air fills in your nitrox tanks. There's no rule saying that you cannot use good old EAN21 in nitrox tanks.

Also, for those of you who have cited grade E standards, I recommend you look at the standard. IANTD and the Navy allow less volatile hydrocarbons in their air than is allowable under regular grade E standard. What I am saying is that air can be within E standards and still leave hydrocarbons in your tanks. That's why our shop exceeds grade E by using IANTD standards, which are more stringent.

 

[4sak3n]

Ummm ... am I missing something? You can get a "best mix" with banked nitrox assuming that your "best mix" has an O2 % less than the highest mix available. All it takes is a bit of maths and the same basic theory that goes into PP blending. The only difference is that the tank still never sees an O2 % over 40.