Continuous Mix Blending  

I found a used Rix SA-6B compressor that was in good shape, and have set it up in the garage for Continuous Mix Blending of Nitrox and Trimix.  Many thanks to Vance Harlow and his book, the Oxygen Hacker's Companion, which is a must read for home mixing.  A modified version of his Nitrox Blending Stick is used to mix nitrox and it works like a charm, dialing in the correct mix, the first time and every time!

The was compressor completely re-built, including new cylinders, bearings and pistons, so it's essentially a new compressor at about half the price.  The motor is only a few months old, and came with the starter, hour meter, and a safety pressure cut-off switch.

I added a 32" Hyper-filter stack after the compressor (mostly to keep the air bone-dry), which keeps the air very, very clean.  I also had the air tested recently, and the results were much cleaner and drier than any of the local dive shops, easily satisfying the requirements for Oxygen Compatible Air (OCA).

For an Oxygen Analyzer, I use my trusty El Cheapo II, which I built about 8 years ago, and is on it's third sensor.  The Oxygen regulator is an Ebay special that cost me $26 and works like a charm.

I did have to install a new 30 AMP breaker in my panel to feed the 5 HP, single phase motor.  Although the compressor is only a few feet from the panel, so I didn't have run much wire (10 gauge due to the short run) to the motor. 

I was also fortunate to be able to add a Masterline Oxygen Booster to the "dive shop" in the garage.  This has helped tremendously with scavenging helium and keeping the costs down.  You can read more about it here.  Somehow, over the past two years I also seem to have acquired 4 T-bottles of Helium, 5 Oxygen Cylinders and 1 Argon Cylinder.  Isn't it amazing how they just seem to "multiply" when you aren't looking?

I recently built a Tank Tumbler for the dozens of steel tanks that always seem to be hanging around the fill station.  This seems to be a popular DIY project and has even proved popular with my Local Dive Shop as I occasionally tumble Nitrox Tanks for the shop.

Did you ever wonder what the cost is to run a Nitrox Fill Station?  I just checked my fill log and in the first three years of operation, I have filled more than 1150 cylinders with Nitrox or Trimix.  This equates to about 250 hours on the compressor and about 25 hours on the booster.  I have also used 40 T bottles of Oxygen (~ $18 each), 19 T bottles of Helium (~ $70 each) and 6 bottles of Argon (~ $70).  You can do the math, I don't really want to know the answer!    I also replace my filter (~$42) every year even though it was only about 10% spent.   It's better to be safe than sorry.

Scott is a certified Trimix Gas Blender (IANTD) and Cylinder Inspector (PSI).