Continuous blending (English)
OK, fresh start with the blog.
Lets start with re-posting some interesting old messages.
Partial blending is very simple, but it's not very efficient.
Once the pressure in your storage bottles starts to drop you soon can't remix your tanks anymore and have to (partially) drain them.
Therefor you need more oxygen and helium then necessary, and the compressor will also have to run more than would be necessary...
A simple and relatively cheap solution is continuous blending with a nitrox stick
You can find a lot of information about this in the oxygen hackers companion from airspeed press.
A must read for everyone who want to start blending himself.
With such a nitrox stick you can bleed oxygen into a mixing chamber where it blends with the air that's sucked into the compressor; so you'll actually pump nitrox.
The big adavantage is that you can always top-off your nitrox tanks, no matter how much pressure there is still in them or that your oxygen storage bottles are almost empty.
Topping off with nitrox is very handy, especially since almost every GUE standard mix can be made by topping off helium with nitrox 32%
Even for decompression mixes it's handy if you for example can top-off with 40% nitrox instead of air... because you'll need to mix less O2 with partial pressure blending first.
For safety reasons it's not advisable to pump richer mixes than 40% through your oil lubricated compressor.
In the picture below you can see the initiel setup.
On the left side is the oxygen buffer with flow restrictor.
The oxygen runs to the op of the stick where it is injected in the airflow of the compressor intake.
Inside the stick are multiple chambers causing lots of turbulance so the oxygen mixes well with the air.
At the bottom is an O2 sensor where you can measure the oxygen percentage that enters the compressor and your tanks.
Eventually the nitrox goes via the yellow hose to the compressor where it's pumped into the tanks.