Dumb stick question

[clownfishsydney]

I just put some baffles in, this works perfectly. I can get within 0.2% every time.

PS to the person who asked, it is a way to create Nitrox, you let air in one end, introduce oxygen just inside this, it mixes, comes out the other end and into the compressor intake hose. Thus you get Nitrox in your cylinder.

 

[kwinter]

I haven't built a stick since I only use a booster and don't have a compressor, but isn't 4 inch pipe a bit large?

 

[rddvet]

I haven't built a stick since I only use a booster and don't have a compressor, but isn't 4 inch pipe a bit large?

I think so. Mines 3 inch and I haven't seen many 4 inch sticks, but I just assumed he had a large compressor.

 

[FoxHound]

Yup 4in is pretty large, the only reason I'm making one that large is because that's what is plumbed in already. I want to be able to remove a small section of what's already there and plug this in.

The compressor itself is a 7.5cfm

 

[clownfishsydney]

I think I used 65 mm (say 2.5 inch). I would think that for a small compressor too big would mean oxygen may not get sucked in as well and mix as well.

 

[Scubadude_LA]

My setup works spot on. I use a 24" section of 3" pipe and it if filled with bioballs. I also have two 16oz cups full of holes, cut down and stuffed in the inlet and outlet to keep the bio balls form spilling out. I also kept the bottom pvc fitting where the hose that leads to the compressor attaches loose (removable). I put my O2 sensor inside the pvc pipe. This is for a 4.9cfm compressor.

IMO, you need a lot less agitation inside the sticks than some people think.

Big thing to watch is how much resistance to flow you have in the system. I used a filter on top of the stick but it was too restrictive, I now leave it off since I still have a filter at the compressor inlet. Set you analyzer to 20.9 with the compressor off, then start the compressor and see how much it changes, if it's more that a few 10ths I would look at your setup and try to minimize resistance.

If you haven't already, I would look into a contactor on the motor and a shut off solenoid for the O2, pretty easy and cheap for the safety you gain.

 

[FoxHound]

The last one i built used baffles, i originally put too much in and the o2 level dropped a bit, took out some and good to go. Nice consistant readings

Sent from my HTC One X

 

[Doc Harry]

other dumb questions = what is a nitrox stick supposed to do ? and at what working pressure ?

A Nitrox stick merely provides thorough mixing of intake air and injected oxygen.

By the time the gas reaches the oxygen sensor at the end of the stick, the gas should be homogenously mixed.

Youe are adjusting the flow of injected oxygen in order to get the desired Nitrox reading at the O2 sensor before it goes into the compressor. If your gas is not mixed homogenously, then the O2 reading will bounce around a lot as the heterogenously gas flows past the sensor.

Working pressure is ambient. If your Nitox stick generates too much resistence to airflow, your compressor will actually have to pull against a small relative vaccum, which will wear out the compressor faster and also generate erroneous O2 readings at the Nitrox stick sensor. Remember that the O2 sensor actually measures O2 partial pressure, so if the pressure at your O2 sensor inside of the Nitrox stick is slightly less than ambient (because of a small relative vaccum), then you are going to get an erroneous O2 reading.