Propane and propane related accessories

[surlypud]

Given that an acetylene refill is now $45 (around Indianapolis) and based on Doug Fattic's excellent post on propane, I decided to switch. I even went so far as to pick up a used oxygen concentrator. I noticed that when the torch isn't connect to the oxy con, the flow rate can be maxed at 10 LPM (invacare platinum 10), but as soon as I hook up my torch, the flow rate drops to 4 LPM. I'm using a Meco Midget torch with a #5 fuel tip (which is bigger than the aw207 Fattic recommends). It seems like the problem is the internal restrictions of the torch body, not the tip or the line. I tried increasing the pressure of the oxy con output, but it had no effect. I don't seem to be able to get enough O2 out to really take advantage of the #5 tip. Do folks who use the uniweld or smith torches see a drop in flow rate? Do you feel like you get plenty of oopmh from your oxy concentrators?

[crumpton]

i cant help you with flow rate issues but I can say the a Meco #5 is HUGE... i was a Meco guy pre-carbon and i did everything with a #2.

anyone else?

[Will Neide]

I don't use a concentrator, but with my Oxy-Propane set-up I've settled into using a #3 tip. If I need a smaller flame I just turn it down. I have a uniweld torch so I don't know how that translates into the Meco, but I'm guessing the #5 is fairly large.

[Doug Fattic]

The oxygen concentrator that you have has twice the output capacity of the 5 lpm unit I have. Mine has enough power to supply oxygen to a Victor TEN-4 tip (which is s bigger than your Meco #5). So it wouldn't seem like your capacity is too small. Are you adjusting the knob that controls the oxygen flow? That is where I would start the investigation. Also do you have a flashback arrestor in the oxygen line somewhere?

[surlypud]

The #5 tip is big, its why I got it.

I did some investigation the other day and when I disconnect the O2 line from the torch, the flow rate from the oxygen concentrator is normal. It can be adjusted from 1 to 10 LPM. With the flow meter wide open, giving 10+ LPM the flow drops to 4 LPM when the torch is connected. I don't have a check valve or flashback arrestor on the O2 line. I tried disconnecting the neck and the tip from the torch, and that had no effect on the flow rate. It seems like torch internals restrict the flow and the concentrator cannot put out enough pressure (9 psi) to overcome the back pressure of the torch.

I just wondered if anyone else ran into this same problem. I'm trying to determine if there is a problem with the concentrator like maybe the compressor needs to be rebuilt. Or if the torch is the problem. I don't really feel like investing in a Smith just to work this out (already got a lot invested in the Meco).

[Pritchett]

I use a Devilbiss 525DS that I found used locally with just a couple thousand hours on it.

Using victor tips for both propane (#2 and #3) and acetylene (#00-#2), it has no problems putting out a full 5 LPM if I crank up the knob.

I would try your torch on another oxygen concentrator, or try another oxycon with your torch if at all possible. I fear you may have a weak compressor...

Also - try removing any unneeded filtration. If your filters are clogged, the combination of torch restriction and filter restriction might be too much for your compressor.

I'm a total noob and had to give up on propane after seeing how much easier it was to fillet braze with an acetylene set-up. If fillets are your method of choice, be warned that it is more challenging to keep localized heating under control. I somehow missed this in all of Doug's posts on the subject, though upon re-reading, he does mention that his students only prefer it for lugged construction.

Still haven't built an actual frame yet, but fillet brazed my bench, work stand mounting and have done piles of practice joints.