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Tips, Techniques, and Questions -- Technical questions or tips

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  #1  
Old 2021-10-23, 12:40pm
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Default Neutral Flame Problems on New Bobcat

Hi everyone. Hope someone can help. I have used a Nortel Minor torch for about 12 years. Recently I purchased a GTT Bobcat and am having difficulty finding a neutral flame. I use a 5 LPM Oxycon and a propane tank at 5 PSI. It seems I can't get away from the reducing flame as you can see. No matter how I adjust, I can't get the cones to align. The O2 is up as high as it can go. Maybe I'm just not used to how the new torch should look???? Please let me know any thoughts or helpful hints you can give me. I appreciate it very much.
Sheri

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Old 2021-10-23, 1:23pm
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Sheri, I'm not using a Bobcat, but on the Minor, I have my propane set at 3 and the oxycon set at about 4.5-4.7. Try that and see if it helps.
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  #3  
Old 2021-10-23, 6:56pm
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Aye, on my GTT Cricket I keep the natural gas really low compared to the oxygen.
Like 25% of the oxygen.

Maybe you are lighting the fuel first and then bring up the oxygen to go for the flame chemistry you want but you reach the maximum available oxygen before you get there.

My thought is to light the fuel then turn it down as low as you possibly can before bringing up the oxygen.

If you can't get the neutral flame you are after then you are going to have to hunt up a 10LPM oxycon or go to tanked O2.

Good Luck with it.
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Old 2021-10-24, 4:24am
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I'll echo what everyone in this thread has said so far. I run a Bethlehem Champion and I have my Propane set to about 1.5 PSI.
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Old 2021-10-24, 7:15am
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As others state, the fuel should be about 1/3 the pressure of the oxygen.

5-7psi fuel is the ideal for bobcat or lynx, but that's when you're running 30psi of oxygen, so you have to adjust down for proper mix ratio.

5 lpm oxycon is definitely on the low side for oxygen supply.

Good luck!
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Old 2021-10-24, 7:43am
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I ran a neutral flame on a 5L oxycon set at 4 and a bobcat for several years. I think my propane was on 3.5. It definitely does not max out the potential of the torch, but very doable for beads. I upgraded to an M15 after a few years, as I started making bigger beads.
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Old 2021-10-24, 7:44am
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Also: purity can be an issue if you run an oxycon as high as it will go. That's why mine was on 4
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Old 2021-10-24, 8:19am
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HHmm. I will try running the propane a bit lower today and see if that helps and will add in the o2 slower. Thank for the great ideas. I'll let you know.
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Old 2021-10-24, 8:23am
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one more thing...if my max O2 with the oxycon is 5lpm, what do you think the ideal psi for the propane should be set at? Math is not my thing.
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Old 2021-10-24, 9:43am
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I would not set my oxycon at 5. I would set it at 4, and then my propane at 3.5-4. That is how I ran mine. If that doesn't work, back down on your propane incrementally until you get something that works. That is how I would approach it.
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Old 2021-10-24, 1:06pm
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Well, turns out it's definitely my oxycon. I switched to another unit that my friend owns and I was able to get in a neutral flame. Mine reads 17596.7 on the counter. I assume that's the hours. Does that mean it's hit its max life? Looking at the filter inside needs changing but not sure if that will help. Opinions?
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Old 2021-10-24, 2:45pm
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The number of hours is kind of irrelevant, up to a point. Mine has well over 27,000 hours and still running strong. I don't know for sure how a dirty filter will affect purity, but it darn sure isn't good for the machine.
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Old 2021-10-24, 3:22pm
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My oxycon has a total of 3 filters;
1) A coarse one that keeps the dust bunnies and hair and larger what-not away from
2) the intake air filter.
The 3) output also has a super fine bio filter that keeps any micro sized stuff from going the oxycon directly into the patients lungs.

People talk about having the 'sieve beds' repoured, especially if they are talking about taking your money to do it, but I don't see the need unless you are overhauling an oxycon that has been in a flood or in tropical humidity so thick and for so long that you suspect mold has taken up living inside the machine.

The used medical ones you can buy on Craigs List don't need anything like that kind of work unless you are trying to make usable as a medical device again which then needs to be serviced by a certified technician and then it needs to be prescribed by a doctor.
The units used for patients do (or did) need to be overhauled about every two or three years.
Filers get replaced and often they put in new tubing because it tends to get brittle and crack or loosen in a few years even if not used.

For non medical use, we can replace the tubing with stuff you can buy at the hardware store.

I found this site some years back that might help;
http://www.frankshospitalworkshop.co...equipment.html


Also the oxygen purity drops off when you push it to the maximum out put but even at its best it only get 97% pure oxygen.
When you run even a brand new medical 5LPM one at 4LPM it outs out about 97%.
But if you push it to 4.75LPM the quantity (volume) of the out put goes up but the purity goes down to as low as 91% and often it can get down to 86% and this only gets worse the more thousands of hours it gets used.

Commercial welding supply companies tanked oxygen often have much higher purity approaching 99% but they can afford industrial units that are tens of thousands of dollars to do that.

Btw welding shops sell and rent small tanks in a range of sizes down to 20 pounds in weight so you can get tanked oxygen in lots of different sizes. You just have to be willing to pay more per cubic foot of oxygen in the smaller sizes.

But it is nice, when you are creating master pieces and are willing to pay for the convenience of having lots heat when and where you want it.
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Last edited by Speedslug; 2021-10-24 at 3:35pm.
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