HP's or LP's for Nitrox?

[Mverick]

Well we both know that there is more than one way to skin a cat..

LOL, Yea, I'm not big on cats though. I'm a dog person..LOL

No, I don't and won't dream of storing O2 at such a high pressure. You just lay in the O2 first and then add the appropriate top off gas. And I agree. All of this would be hard without a fill panel..

I fill my RB cylinders off my booster to 3000 to 3500psi all the time. Just do it slow. And keep everything clean. But banking pure O2 to 4500psi is a pain. Need a good panel and booster set up. Set up for Pure O2. And I'd rather not. Super expensive.

This tread start as “Which is better, LP or HP”. I think we would both agree. It is completely a personal preference.

Well, Not really agree. Thread start was "Which is better for Nitrox, LP or HP". And I still think it's easier to blend in a LP tank. You don't have to build as much pressure when topping off. So you create less heat from compression. Which is good. You also have a shot at not dumping the gas to build another mix. Or, More of a shot then a HP.

I have both HP and LP tanks. Lucky I guess. And almost all my blends are done in the LP's. It's just easier. And uses less gas for me. If your shop has all the equipment for it. Yea, Your not gonna have a problem. But if it doesn't. LP's are easier again. Not all shops have the equipment.

If they charge you $12 a fill no matter what. Then having them dump and fill isn't going to cause you a problem.

But an 80/20 deco blend in a 3000psi tank needs 2400psi O2. And O2 is usually 2400psi tank. So if you want a 80/20 in a HP. You'd need to put more pressure in the tank then you could get from a O2 cylinder. You'd have to use a booster. And all shops don't have them. None in my area have boosters.

And if you ever want to fill your own. Much easier again with LP's. Have your shop top off with air. You add the O2.

 

[nyresq]

quote "But an 80/20 deco blend in a 3000psi tank needs 2400psi O2. And O2 is usually 2400psi tank. So if you want a 80/20 in a HP. You'd need to put more pressure in the tank then you could get from a O2 cylinder. You'd have to use a booster. And all shops don't have them. None in my area have boosters."


if you're topping off with 50% nitrox instead of air, then you wouldn't need the full 2400 O2 in the tank first. assuming the 50% is banked at 3000 or higher, you wouldn't even need a booster.

 

[Charlie19]

My new boat has a 4 tank rack that is mounted to the back of the standing bolster. Each holder measures 7.5" ID. Looks like I'm constrained to using HP's if I want to use this rack.

This has got to be the most ridiculous reason for choosing which tanks to use that I have ever heard.

Don't use the rack. Readjust the size of the holders. Buy 7" LP tanks (OMS' 85s come to mind). Install proper size tank holders. You can afford a boat, but can't afford to replace the tank holders? There are lots of different possibilities you can explore.

Dempsey of the Deep

 

[Mverick]

quote "But an 80/20 deco blend in a 3000psi tank needs 2400psi O2. And O2 is usually 2400psi tank. So if you want a 80/20 in a HP. You'd need to put more pressure in the tank then you could get from a O2 cylinder. You'd have to use a booster. And all shops don't have them. None in my area have boosters."


if you're topping off with 50% nitrox instead of air, then you wouldn't need the full 2400 O2 in the tank first. assuming the 50% is banked at 3000 or higher, you wouldn't even need a booster.

Thanks for biting on the question. Now, what if the shops in the area your diving DON'T Bank Nitrox? NONE of the shops in my area do. Out of around 8 shops. So you have a nice HP that you can't get a full Nitrox fill in. because there O2 cylinder bank has low pressure from filling alot of nitrox. Only a partial. Yet, if you'd of bought a LP. You'd have a much better chance of getting a full fill.

Plus, if you ever want to blend your own. Which isn't difficult. And alot cheaper. You can do it yourself with a LP. With a HP. You'll be wasting alot more gas from dumping your cylinder....

Buy the cylinder for the task. If you only want to use it out of your home shop. And they can do the fills. Fine. Otherwise. Get a LP.

 

[Genesis]

C'mon guys and gals, let's be honest with people here and not play strawman games.

First, a deco cylinder is probably going to be an AL40 or 80. Anything else is kinda dumb for a deco cylinder. So scratch that argument.

Second, here are some REAL numbers for PP mixing LP (2400) and HP (3500) cylinders in terms of PP O2 add amounts:

3500 psi - 469psi of O2.
2640 (2400 + 10%) - 363psi of O2.

(Both using the "Z" factor)

If 100 psi on the O2 add makes the difference for you, then you need a second tank for your O2 supply cylinders.

As for the heating factor on fills, you get pretty good at figuring out how much you must overfill (which is legal, by the way, as the rated pressure is AT 70F) to get a proper cold fill pressure - which is what the formula is calculating for.

I regularly hit my target mix within 0.2% indicated on my O2 analyzer - well within the analyzer's tolerances.

If you are buying shop fills and the shop CANNOT fill 3500psi tanks to rated, then find another shop. If there are no other shops, THAT is a valid reason not to buy the HP tanks.

The rest of this is armwaving.

 

[MXGratefulDiver]

I regularly hit my target mix within 0.2% indicated on my O2 analyzer - well within the analyzer's tolerances.

If you are buying shop fills and the shop CANNOT fill 3500psi tanks to rated, then find another shop. If there are no other shops, THAT is a valid reason not to buy the HP tanks.

The rest of this is armwaving.

Well, you're a better man than me ... I can usually hit LP's within 0.3% or so, and HP's to within 1.0% or less. If they're left overnight to cool and get topped, then they're pretty much right on regardless of what kind of cylinder it is.

... Bob (Grateful Diver)

 

[Mverick]

C'mon guys and gals, let's be honest with people here and not play strawman games.

First, a deco cylinder is probably going to be an AL40 or 80. Anything else is kinda dumb for a deco cylinder. So scratch that argument.

Second, here are some REAL numbers for PP mixing LP (2400) and HP (3500) cylinders in terms of PP O2 add amounts:

3500 psi - 469psi of O2.
2640 (2400 + 10%) - 363psi of O2.

(Both using the "Z" factor)

If 100 psi on the O2 add makes the difference for you, then you need a second tank for your O2 supply cylinders.

As for the heating factor on fills, you get pretty good at figuring out how much you must overfill (which is legal, by the way, as the rated pressure is AT 70F) to get a proper cold fill pressure - which is what the formula is calculating for.

I regularly hit my target mix within 0.2% indicated on my O2 analyzer - well within the analyzer's tolerances.

If you are buying shop fills and the shop CANNOT fill 3500psi tanks to rated, then find another shop. If there are no other shops, THAT is a valid reason not to buy the HP tanks.

The rest of this is armwaving.

LOL TRUDAT.....LOL

Still believe LP is better for mix. LOL.....