Continuous Mix Blending  

I found a used Rix SA-6B compressor that was in good shape, and have set Garage Gas Mixing Station.  Click for a larger up in the garage for Continuous Mix Blending of Nitrox and Trimix.  Many thanks are due to Vance Harlow and his book, the Oxygen Hacker's Companion.  We used a modified version of his Nitrox Blending Stick and it works like a charm, dialing in the correct mix, the first time and every time!

I had the 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, even though this is an oil-free compressor, so there is no chance of any hydrocarbons.  I also had the air tested recently, and the results were much cleaner and drier than any of the local dive shops.

For an Oxygen Analyzer, we used my trusty El Cheapo II, which I built about 5 years ago, and is on it's second 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 my 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 Cylinders.  Isn't it amazing how they just seem to "multiply" when you aren't looking?

The scuba wall in our garage.  Click for a larger image.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 annual cost is to run a Nitrox Fill Station?  I just checked my fill log and in the first two years of operation, I have filled more than 750 cylinders with Nitrox or Trimix.  This equates to about 125 hours on the compressor and about 15 hours on the booster.  I have also used 25 T bottles of Oxygen (~ $18 each), 12 T bottles of Helium (~ $70 each) and 4 bottle of Argon (~ $70).  You can do the math, I don't really want to know the answer!    I also replaced my filter (~$42) after one year of use, and found that it was only about 10% spent.   It had plenty of life left in it.

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