Partial pressure nitrox fills at home?

[johndiver999]

True... but assuming "worst" case of 1 T rental, and only 1 scuba cylinder ... so you return with say 400psi because you don't have another cylinder to fill any more O2 into... and need to return the cylinder to swap to a fresh one... or dive weaker nitrox.

Multiple dive cylinders, and multiple T cylinders can mitigate that by cascade filing and the like, but now is that extra $$ worth it? Does one have that much space? It all depends... And with having supply cylinders that low, you're draining your diving cylinders every time for a fill (to use up the last 20% of O2)... is that worth the extra T cylinder rental (or purchase) for returning ~$10 of unused O2?

Also, does that affect your home/renters insurance and/or leases? Does one have a vehicle capable of transporting T cylinders safely? Have a spot to store properly?

As the saying goes, there's many ways to skin a cat... but will it fight back?


_R

what does it cost you for a fill of a bottle of oxygen? Who in the world is going to do their own nitrox filling if they have only one scuba tank? And you don't have to drain your scuba bottles between fills, unless/until the Oxygen bottle is low.

If you have two oxygen bottles and several scuba tanks, you can use the last bit of oxygen with very little waste and it is VERY nice to be able to fill a small bottle with pure oxygen for emergency use on the boat - that alone might provide tremendous value, if the dive shop is not accommodating.

And.. you don't tell your wife or the insurance company what you are doing in the garage.

 

[rddvet]

So I’ve looked into the nitrox stick a lot more. My buddy works at the dive shop and that’s how I get free fills. I most likely wouldn’t be able to just say hey let’s put this DIY stick on the intake for just a hour to fill our nitrox then take it off so no one would notice… so I’ve been looking into simply purchasing my own compressor to do this, since I’d like to be in control of my own nitrox (get it whenever I want and however much I want), have an issue With paying a shop $17 for nitrox, and they said they’d need to keep my tank over a day to do it, also where the shop is located it’s a lot of gas money… so realistically the nitrox fill is $25+ for a tank. For the sake of numbers we can believe more let’s say it’s only $20 a fill for the math I’m about to do.

I’ve found a couple compressors I might like to get. I’ve heard the alkin w31 is good, it’s $3500.

I’ve also come across the coltri msh6 which is $2100, and I’ve heard people mention them too.

Both of these compressors will take about 25 minutes to fill a tank, so a couple hours of filling throughout the week for the weekend.

Compressors that can handle multiple tanks and fill faster are $5500 I believe, so all in what your cost vs outcome is worth to you.

I hope I can find a used compressor, if anyone knows or has one for sale for cheap please let me know.

So let’s go with the $2100 compressor because I like lower numbers.

$2100 (compressor) + $100 (nitrox stick) + $100 hoses + $100 (whatever else) + $500? (cost of gas with rental?) + $300 for maintenance = $3200

$3200 / $20 (per nitrox fill) = 160 fills to break even.

160 fills / 52 weeks = 3 dives a week

So let’s say it takes two years to have it make sense since I don’t think I will be diving every single week.

Now I’ve been looking into trimix mixing using this same method just adding an additional feed for the helium. It seems like it’s a lot more of an artwork than anything, making sure that the levels are correct throughout the whole fill.

Now if I was able to fill trimix with this method it would obviously make a lot more sense.

No offense, but please don't go buying anything at this point. You haven't really moved past the absolute basics of filling at home. Search for the oxy hacker's guide if you can find one and do more reading. There is a section here for people who mix their own gas and a gas blenders facebook page. Do a ton of reading, then consider buying some stuff. But to be honest if your buddy gives you free fills, I would run with it.

 

[rddvet]

Do you know if it’s easy to use a fire extinguisher to put out an oxygen fire?

It is not. A few years ago my wifes car (which hadn't been driven in 3 days) caught on fire in the driveway at 4am and it was parked about 4 feet from the garage door, which has 3 T's of oxygen about 6 feet into the garage. I was crapping my pants waiting on the fire dept. The fire guys tore my soffit and siding all to hell because they had to open stuff up to confirm the fire was fully out. They went a little crazier than normal doing it since I warned them of the oxygen in the garage. I did speak to my insurance (state farm) and was told that if the oxygen was involved secondarily I would still be covered.

 

[JFalzetti]

No offense, but please don't go buying anything at this point. You haven't really moved past the absolute basics of filling at home. Search for the oxy hacker's guide if you can find one and do more reading. There is a section here for people who mix their own gas and a gas blenders facebook page. Do a ton of reading, then consider buying some stuff. But to be honest if your buddy gives you free fills, I would run with it.

No offense taken. I just don’t understand where the point is of ok you can now move onto blending nitrox at home…

From what I’ve read the nitrox is not all that complicated. I understand that understanding the risks is the important part, which is what I’m trying to learn. Realistically I could say I understand the basics of the nitrox stick and could go build one and I personally think I could fill tanks fine with my current knowledge. Again what I’m concerned about is understanding the whys and how’s of the risks and procedures.

It’s like diving. You could know how to dive but not know how to do it safely…

For example I know how to make the nitrox stick I won’t go into detail, but everything touching pure O2 is welding stuff designed for pure O2 the rest is diluted contact after the static mixer. I know that the flow rate is what really dictates the O2 %. I know that you’ll want a blow off valve to make sure there is never more than 40psi of O2 entering your stick. If your compressor shuts off suddenly, clear out your stick since you never want a concentrated amount of O2 going into the compressor. You monitor the O2 at the intake and right after the condenser to verify O2 % going into the bottle because once the moisture is taken out the O2 goes up slightly. I also obviously understand that you test the % from the bottle directly.

I’m planning on reading the oxy book everyone suggests, and I realistically won’t be buying anything within probably the next 6+ months which gives me a lot of time to learn more.

What I haven’t fully understood yet is if the nitrox stick can become a trimix stick…

 

[DeepSeaExplorer]

Might be less expensive to simply buy more tanks so you always have some to dive while others are at the shop awaiting fills.

 

[rddvet]

No offense taken. I just don’t understand where the point is of ok you can now move onto blending nitrox at home…

From what I’ve read the nitrox is not all that complicated. I understand that understanding the risks is the important part, which is what I’m trying to learn. Realistically I could say I understand the basics of the nitrox stick and could go build one and I personally think I could fill tanks fine with my current knowledge. Again what I’m concerned about is understanding the whys and how’s of the risks and procedures.

It’s like diving. You could know how to dive but not know how to do it safely…

For example I know how to make the nitrox stick I won’t go into detail, but everything touching pure O2 is welding stuff designed for pure O2 the rest is diluted contact after the static mixer. I know that the flow rate is what really dictates the O2 %. I know that you’ll want a blow off valve to make sure there is never more than 40psi of O2 entering your stick. If your compressor shuts off suddenly, clear out your stick since you never want a concentrated amount of O2 going into the compressor. You monitor the O2 at the intake and right after the condenser to verify O2 % going into the bottle because once the moisture is taken out the O2 goes up slightly. I also obviously understand that you test the % from the bottle directly.

I’m planning on reading the oxy book everyone suggests, and I realistically won’t be buying anything within probably the next 6+ months which gives me a lot of time to learn more.

What I haven’t fully understood yet is if the nitrox stick can become a trimix stick…

Sounds like you're catching on and realizing there's alot to learn, which is good. My main point is I don't want to see you spend a bunch of money and then realize it was spent unwisely. I'll be happeyto answer questions if you message me. Key points: always go bigger with the compressor than you expect, banks are not necessary just a luxury (you can fill off the compressor. I did for years), having a booster is very, very nice in conjunction with a compressor (I went without a booster for years. Now that I have one I couldn't live without it). Nitrox sticks are easy to make, but to make a very good one there are some nice add-ons like a flowmeter after the welding or oxygen regulator. If you do think about getting a booster, it's hard to beat the USUNs from China. I'm pretty sure they're stolen intellectual property from another company, but they run very well and they're very cost effective. Don't buy a haskel. The long term costs will kill you. I have a nearly $10k electric booster that over 10-15 years will save me a ton compared to if I bought a used Haskell due to the ridiculous costs of haskel parts.

 

[BoltSnap]

having a booster is very, very nice in conjunction with a compressor (I went without a booster for years. Now that I have one I couldn't live without it).

How do you use the booster without a bank system? Inline with the compressor to the tank being filled?

 

[JFalzetti]

Sounds like you're catching on and realizing there's alot to learn, which is good. My main point is I don't want to see you spend a bunch of money and then realize it was spent unwisely. I'll be happeyto answer questions if you message me. Key points: always go bigger with the compressor than you expect, banks are not necessary just a luxury (you can fill off the compressor. I did for years), having a booster is very, very nice in conjunction with a compressor (I went without a booster for years. Now that I have one I couldn't live without it). Nitrox sticks are easy to make, but to make a very good one there are some nice add-ons like a flowmeter after the welding or oxygen regulator. If you do think about getting a booster, it's hard to beat the USUNs from China. I'm pretty sure they're stolen intellectual property from another company, but they run very well and they're very cost effective. Don't buy a haskel. The long term costs will kill you. I have a nearly $10k electric booster that over 10-15 years will save me a ton compared to if I bought a used Haskell due to the ridiculous costs of haskel parts.

Can you confirm that this is the correct book for me to read?

https://gue.com/blog/wp-content/uploads/2022/04/Oxygen-Hackers-Companion-Vance-Harlow-Sanitized_01.pdf

 

[WarrenZ]

That's a good starting point.

 

[TrimixToo]

How do you use the booster without a bank system? Inline with the compressor to the tank being filled?

A booster is basically a special-purpose compressor. It goes between the source tank (O2 in this case) and the tank being filled. There are two common kinds of boosters, air drive and electric drive, with the latter being less common than the former. The part of the booster that increases the pressure of the gas being pumped is isolated from the drive system.

An air driven booster requires a source of compressed air to drive it, such as a shop compressor. A single stage booster (like mine) can pull a source tank down under 200 PSI if you're patient. A two stage booster (I wish!) can pull it down to under 100 PSI. In either case there isn't much wasted gas. They're expensive, particularly the O2 clean variety needed for nitrox and trimix. I haven't checked prices lately but when last I looked my Haskel (the O2 clean version of an AG-30) had doubled in price since I bought it, and it was expensive then. Mine is driven by a shop compressor larger than most people would otherwise have at home, and those are also expensive but not nearly as much so as a booster.

O2 is fairly cheap, so waste isn't that important. Helium cost, on the other hand, makes a booster purchase cost effective over time if you dive trimix and dive enough. As a practical matter, RB users can use smaller boosters and correspondingly smaller shop compressors to drive them than OC divers.

I dived enough trimix to pay for the entire system I have at home *and* the training (Advanced Gas Blender, including O2 clean tech) in savings from shop rates for trimix and nitrox fills for OC.