Nitrox in doubles ?

[gbray]

I have just taken two lp72's in to be doubled. This will be my first set of doubles. I am on a budget so my LDS is rebuilding a used manifold to put on my tanks. They quoted me a package price for the manifold, bands, O2 cleaned and EAN 32 filled. It came out to be a little higher than I had originally figured. I also had not considered O2 cleaning. My question is ...is it worthwhile to have them o2 cleaned? My intent is to practice using doubles to possibly move into more tech stuff in the future, such as wreck or cavern. I made my first dive to over 100ffw this weekend and loved every minute of it. My concern is having nitrox as my primary gas may limit my depth. I don't plan on any deco dives just yet but don't want to push my limits with nitrox. Am I being over concerned ? should I let them o2 clean my tanks?

 

[Blackwood]

If they'll be partial pressure filled, yes. If not, no. If you'll ever get them filled on a boat no.

 

[Puffer Fish]

I have just taken two lp72's in to be doubled. This will be my first set of doubles. I am on a budget so my LDS is rebuilding a used manifold to put on my tanks. They quoted me a package price for the manifold, bands, O2 cleaned and EAN 32 filled. It came out to be a little higher than I had originally figured. I also had not considered O2 cleaning. My question is ...is it worthwhile to have them o2 cleaned? My intent is to practice using doubles to possibly move into more tech stuff in the future, such as wreck or cavern. I made my first dive to over 100ffw this weekend and loved every minute of it. My concern is having nitrox as my primary gas may limit my depth. I don't plan on any deco dives just yet but don't want to push my limits with nitrox. Am I being over concerned ? should I let them o2 clean my tanks?

Personal choice, but having clean tanks is not a bad thing...and there are a lot of dives where you can use low levels of Nitrox... like 25%, that have a fairly deep mod.

If you can afford it, I would have it done...but then almost all my diving is with Nitrox...

 

[halocline]

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. O2 cleaning won't hurt but is almost certainly unnecessary. The nitrox fill is a nice; I suspect that eventually EAN32 will be the standard gas for most recreational diving. You're not required to keep nitrox in the tanks, just fill them with air when you want. Most places have grade E air these days which does not contaminate your O2 clean tanks/valves, but then again you don't need O2 clean tanks for nitrox (under 40%) use unless you're getting partial pressure fills which you almost never see.

If they're saying you need O2 cleaning to get nitrox fills then they are either using an outdated means of filling nitrox (Partial pressure) or they're ignorant about nitrox requirements or they're just trying to get you to spend some extra money.

I doubled my 72s for about $220 if I remember, and that was new 7" bands and a blue steel 200bar manifold from piranha dive gear. You get the vis first, ask the LDS to put only a hundred PSI or so in the tanks, then when your bands/manifold arrive you empty the tanks, take off the valves, assemble the doubles (which is easy) then head right back to the LDS for a fill. If you do it right your tanks will only be exposed to ambient air for a few minutes, and then empty for an hour or so.

 

[ianr33]

unless you're getting partial pressure fills which you almost never see.

If they're saying you need O2 cleaning to get nitrox fills then they are either using an outdated means of filling nitrox (Partial pressure)

We must dive in different places. I hardly ever see anything other than partial pressure fills.

 

[Pearldiver07]

We must dive in different places. I hardly ever see anything other than partial pressure fills.

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

 

[deadly_risk]

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

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.

 

[mike_s]

If they're saying you need O2 cleaning to get nitrox fills then they are either using an outdated means of filling nitrox (Partial pressure) or they're ignorant about nitrox requirements or they're just trying to get you to spend some extra money.

.

Matt. Unless you go to a place that does a high volume amount of fills, I think you'll find that most other shops use partial pressure filling.

it's not outdated. It is just the way it is for small shops.


I wish that our local shops had banked EAN. But I don't know of a shop within hours driving that banks nitrox. However all of them do partial pressure filling (and require o2 cleaning because of it.).

 

[willgr1]

If you're nitrox certified you should be able to answer the first question yourself. If you know how the dive shop is producing nitrox (partial pressure, banked) you should know if the tanks will be exposed to gas mixtures with an O2% higher then 40. If the shop recommended O2 cleaning than likely they are partial pressure blending, which is very common...every shop in my area that i've visited blends this way.

Also, you shouldn't have to worry about your mix limiting your depth because hopefully you've planned your dives accordingly and know what mix is best for that site and what your max pO2 depth limit is.

 

[DA Aquamaster]

The option to not diving nitrox is diving air and 130 cu ft of air is enough to get you into a lot of trouble well above 100', let alone below 100'.

25% works well on dives to 150' and that is at least 20' deeper than you want to go with double 72's and without training in both advanced nitrox and deco procedures. In comparision, 30% will have a PPO2 of 1.4 at 120' and 32% will have a PPO2 of 1.4 at 110' and that is more than deep enough at the moment.

If you plan to use the 72's to get comfortable in the water on recreatonal profiles within the NDL's you are on the right track, but you are currently well short of the training and experience needed to do deco diving.

You have not mentioned what type of manifold you have. Is it a single outlet manifold or a dual outlet manifold and does it have an isolator valve? For your eventual technical diving you will definitely want to have a dual outlet valve with an isolator.