Is it worth it to blend your own?

You need a compressor and you need to rent or buy O2 and He bottles. In addition, for continuous mixing, you will need two devices to manually adjust the mass flow of O2 and He, and you will need two oxygen analyzers with displays (to see how much He is injected into the mixing tube, and later O2). Finally you serve this blend to your compressor. You will also need an O2/He analyzer to see what comes out. You should also invest in magnetic valve that will stop the flow of oxygen into the mixing tube would your compressor lose power. Compressors do not behave well with 100% O2. It might be a wise thing to add such a valve to the He bottle too, as He is expensive. All this adds to the cost, but the system is wonderfull to use. Do not exceed 40% O2 and 200 bar (the rest can be air), to make sure nothing funny happens inside the compressor. I am sure, that there is some legislation governing fill stations and the use of pure oxygen, so please make sure you know the local laws.

Alternatively, you could do partial pressure fills with He and O2 and then top with the compressor. Simpler setup but more work in the long run.

 

Smell is bad. Make sure the air intake is far away. Electric compressors are much preferred but they may require a more robust electricity supply than the average wall socket.

 

Gas fills at home might become economical if you dive a lot. The simpler the setup (air > nitrox > trimix) the quicker the equipment pays itself back.

If you do partial pressure nitrox fills then you need oxygen clean cylinders. With constant flow mixing you won't.

 

For a RB? Don't bother unless logistics for the LDS are really challenging for some reason. Get a few large LP singles and a small booster instead. Invest the difference well (smile).

I bought a Mako (Bauer) K14-85 for $1200 from craiglist. I converted to electric from gas for about another $800. I added two used towers at $500 each and it passed OCA. I did various other upgrades to be able to run it to 3800 PSI (the current shutoff pressure) from its original maximum of (IIRC) 3200. With better cooling I could run it up to 4500 but it's fine for me as-is. The high-ticket item for me was the new Haskel AG-30 at something like $3.5K at the time. Oil changes every 2 years, new filters once a year, and air tests--also annual-are all the compressor has needed aside from a new 4th stage head. They cost a few hundred bucks a year, much less than I save. I have a bunch of spares (valves, mostly) ready to go in a box that I have not yet needed.

I think I got most of the bank tanks for $150 each. I have six, but more than four is a luxury, really.

This setup paid me back after 3-4 years of blowing a fair number of helium bubbles. I'm paying under $100 for my typical 18/35-ish mixes while others in the area are dropping $250-300. A trimix analyzer is part of the equation as well. Without one, I'd have to blow down the tanks and start over every third time or so to keep the He percentage within reasonable margins of error. I never do that. I analyze and mix on top. (If I can't do that, I use the Haskel to transfer some mix to a dedicated trimix storage T bottle.)

YMMV....I have been pretty lucky with my "pig in a poke" compressor. All I did was verify how long it took to fill an AL80 before buying it. It met spec, so it's in the garage.

I love having my own, though. It often takes less time to mix than to go to the dive shop twice, and they're not far away.

 

A booster and compressor are never a cost savings, but they are a huge convenience. With my electric booster, compressor, and all the hardware I'm in the $18k range. But it was put together over several years. I couldn't live without my setup. It's a time saver and I enjoy messing with it. If I was doing it again and wasn't hard set on wanting an electric booster, I would get a K14, build a trimix stick, and buy one of the USUN boosters from China. Several people have had excellent success with the USUN boosters, and you can get one with spares for under $2000. I was very skeptical because so many things from China are poor quality, but these boosters seemingly are working great. I always recommend people avoid haskel when possible. They make great boosters, but they rape you on the service parts. On some of the Haskels if you pay full retail for a complete service kit can be almost $2000.

 

Retail cost for Haskel overhaul parts, on AG-30 O2 service kit, is $800. Cost for AGT-15/30 O2 service kit is $1500. A 10% discount is available from American Airworks in WV. Reference "Scubaboard Discount". The good news is a properly completed overhaul should provide 1,000,000 strokes or 2000 hrs of continuous operation at 50 CPM. Many 1960 model Haskels are still in active duty today. Safe diving to all.....

 

When I was looking at Haskels I was looking at a 15/30 and got quotes from $1300-2150 for the rebuild kits. American Airworks was right above $1400 and were great to work with and talk to. But ultimately a Haskel wasn't for me.

 

Thanks everyone for all your thoughts and insights. Scubaboard can make you wiser very quickly on certain things and this happens to be one of those moments. At my present certification level and with the TDI Trimix course in process, my own diving will remain above 200 with most of the dives in the 150' or shallower range. Based on what I have read so for, am I correct to realize that if I carry O2 and Helium then that would be a more manageable set up than air compressing. I can top off air at LDS and that takes away one of the major hassles involved in blending your own?

Thanks once again for all the help.

 

A major unknown for anyone thinking along these lines is the availability and price of helium. A friend with whom I dive has worked hard to get a personal setup, buying a good used compressor and a lot of other paraphernalia. When he contacted the local outlet for a major national gas supplier, he as told he could open an account, but they would not be able to give him UHP helium on that account. If they did become able to get it for him, the price would be astronomical--he could purchase trimix at marked up retail pricing for far less. His solution was to walk into the same outlet, act as my employee using my account number, and get the helium for roughly 1/5 the price he was told he would have to pay on his own account.