Mixing Stick Question

[vbcoachchris]

I have a 24'' Oxyhacker mixing stick made exactly like the manual depicts. It works great on my Alkin W31 (3.5 cfm), but I recently sold my W31 and bought a Mako 10 hp (13 cfm). The manual says to upscale the design for compressors larger than 8 cfm.

Does that mean longer pipe, larger diameter pipe, more baffles, larger air intake opening, larger diameter holes in the baffles, etc or all of the above?

I am currently just using a standard medical regulator. Will this still work or do I need to drill a large orifice.

I realize it depends somewhat on the compressor, but if I could get some advice on a baseline to start with, I would appreciate the help.

Scott

 

[dannobee]

You'll probably have to upscale a little bit.

The way to check is to use a manometer on the inlet and check for the pressure drop. 1-2 inches of water would be ideal. Anything more than, say, 5 inches of water would reduce the output of the compressor.

A manometer is easily made with clear vinyl tubing and colored water. Attach to a piece of cardboard or wood.

 

[vbcoachchris]

You'll probably have to upscale a little bit.
QUOTE]

So where do I start?

3'' tube?
30"-40'' tall?
will my medical o2 reg work?


Scott

 

[dannobee]

So where do I start?

3'' tube?
30"-40'' tall?
will my medical o2 reg work?


Scott

3 inch tube-even a 2 1/2in tube should provide sufficient flow. Shorter length pipes actually improves air flow, not longer pipes.

Medical regulator will need the restriction drilled out. If you have some small number drills (61-80) and a pin vise, you can measure the diameter of the current restriction and increase the size accordingly.

Compute the difference in AREAS, NOT the diameters. If your new compressor has 3 times the output, you'll need to triple the area of the hoses and tubes. Likewise when drilling out the orifice of the medical regulator. Just remember that the gauge reading in CFM/LPM won't be accurate.

My trimix stick doesn't use baffles, I made annular discharge ring insert instead of the more restrictive baffles.

Verify any restriction by measuring with a manometer.

 

[pescador775]

The regulator is probably 60 psi/15 lpm and the orifice is probably 0.025 (#73). If that is confirmed, drill it out with a 0.052 drill (#55).

One might start with a slightly smaller drill should that compressor output less than 13 cfm or if the regulator is 100 psi.

What is actual liter flow as shown on the gauge for 36%, currently?

 

[vbcoachchris]

36% was the highest I could obtain (15 lpm) on my W 31

 

[pescador775]

Examine the low pressure gauge (liter gauge). At the bottom of the dial there should be a notation as to orifice size. For example, "73". If not, check the nozzle to which the feed tube is attached. What is make and model of regulator?

If the new compressor is actually 13 cfm, the regulator orifice will need to be four times larger, eg, the drill size should be doubled in diameter.

 

[vbcoachchris]

I made the stick
3'' PVC 24'' long
practice golf ball chambers for baffles

Drilled regulator orrifice to #68

Now I get only a .2 PPO2 change when the stick is connected, but I get a 4% difference in pre and post O2 readings. I ahve trieid 3 different O2 sensores all with the same result. in 32% out 28% or in 36% out 32%. Any ideas what could be causing this?

Scott

 

[pescador775]

I made the stick
3'' PVC 24'' long
practice golf ball chambers for baffles

Drilled regulator orrifice to #68

Now I get only a .2 PPO2 change when the stick is connected, but I get a 4% difference in pre and post O2 readings. I ahve trieid 3 different O2 sensores all with the same result. in 32% out 28% or in 36% out 32%. Any ideas what could be causing this?

I have no idea what the first sentence means. Do you connect and disconnect the stick routinely? Saying "when" the stick is connected, do you actually mean "after" making the connection, or "while" the stik is connected? Connection to what, the compressor? What about the small, .2, oxygen percentage change, is that a range from low delivery pressure to high, or something else? What means pre and post readings? Is that measurements done at the base of the stick and the output of the compressor? What is the reading from the tank?

I'm guessing that the huge stick is channeling. If so, a 2.5 inch stick should improve things. Get rid of the golf balls and insert some steel pads like Gottschalk steel sponge or other quality scouring pad. Also, a #68 orifice would almost certainly starve the oxygen flow. At minimum, a #60 would be needed, eg unless there is something not disclosed about the regulator or compressor. The gauge dial should read 10-12 lpm at 36%. If you are trying to strangle the regulator to prevent mixtures above 36% I can understand that but don't goof up the process somehow.

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[vbcoachchris]

I have no idea what the first sentence means. Do you connect and disconnect the stick routinely? Saying "when" the stick is connected, do you actually mean "after" making the connection, or "while" the stik is connected? Connection to what, the compressor? What about the small, .2, oxygen percentage change, is that a range from low delivery pressure to high, or something else? What means pre and post readings? Is that measurements done at the base of the stick and the output of the compressor? What is the reading from the tank?

I'm guessing that the huge stick is channeling. If so, a 2.5 inch stick should improve things. Get rid of the golf balls and insert some steel pads like Gottschalk steel sponge or other quality scouring pad. Also, a #68 orifice would almost certainly starve the oxygen flow. At minimum, a #60 would be needed, eg unless there is something not disclosed about the regulator or compressor. The gauge dial should read 10-12 lpm at 36%. If you are trying to strangle the regulator to prevent mixtures above 36% I can understand that but don't goof up the process somehow.

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I hooked the O2 sensor up to the compresor without the Nitrox stick connected and calibrated it to 20.9. Then connected the stick and turn the compressor on it. The O2 reading only dropped to from 20.9 to 20.7. I have an pre analyzer to measeure the O2 content entering the compressor intake and a post analyzer to measure the O2 content actually going into my banks. There is a 4% difference between these and there is nothing wrong with either analyzer (iIchecked them both on multiple sources).

The golf balls worked well on my last stick, so I thought I would try them again. Do you think the scouring pads will address the 4% drop in O2?



This compressor is 3 times the size of my old one, My old regulator gave me 32% at 12 lpm with a #77 orifice,. A #68 orifice is 3 times the size (area) of a # 77 orifice.

This was my reasoning for the #68 orifice.

Scott