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.

[Doug Fattic]

Surlypad, my shop in Niles, Michigan is straight up US 31 about 150 miles north of Indianapolis and 10 miles north of South Bend, Indiana . I'm only a couple of blocks off of old 31. It is about a 2 1/2 hour trip. Bring your torch and concentrator and we can swap things around to see if everything is working properly. My next framebuilding class starts December 2 so come before or after that (or stay for a couple of weeks for class :).

I'm now suspicious that your concentrator is putting out enough oxygen to run your Meco #5 tip at 4 lpm. Of course this is just a guess on my part. Is your flame starved for oxygen when you have adjusted for the right amount of propane? In other words you can't get the flame to start to turn a bit blueish? Really it doesn't matter what your lpm meter is saying. I adjust the volume of the flame by listening its hissing sound. If it is too quiet I add more propane 1st and then adjust the oxygen until the color of the flame just starts to shift from greenish to blueish. If the oxygen can't keep up I turn the concentrator's regulator knob up more until it can. If I am using a Victor #3 tip (which is just smaller than your Mico #5) my DeVilbiss 515 meter will read just higher than 3 lpm. If I have my big Victor TEN-4 tip my meter will be around 4 lpm. The reading on the lpm meter will change with a different tip size even though I keep the oxygen adjuster knob on the OC the same. Keep in mind my concentrator is a 5 lpm unit. My concentrator even works with a Smith rosebud – which of course requires even more propane and oxygen.

I agree with Pritchett that acetylene has a finer, hotter frame than propane and is easier to fillet braze with it – especially for those starting out. This is where acetylene has the biggest advantage. However I will add that Herbie Helm and I can lay down just as nice a brass fillet with propane as we can with acetylene. You couldn't tell any difference between a fillet we make with either. When Herbie does the fillet brazing demonstration in my class, he can lay down a perfect fillet with propane (even though his job is greatly complicated by the fact that he has to explain his motions while demonstrating the correct torch movement). Sometimes he will use acetylene if 2 out of the 3 students will use acetylene in the future. So experienced brazers can use either one effectively.

A hotter flame can braze a joint faster but it can also get one in trouble quicker too. For that reason I find students can learn silver brazing a little easier with propane (with its bigger, cooler flame) than acetylene (with its smaller hotter flame). In summery, the primary advantages of propane is that it is much cheaper, easier to transport and there are many more locations with longer hours where it is available. If those things aren't so important than acetylene would be my 1st choice.

[surlypud]

Thanks Doug, that is a great offer. I will call you to work out the details for a visit.

-Chris

[veryredbike]

It should be noted that I got more flow out of my concetrator by opening it up and removing the hepa filter. As long as you're not breathing it, it should be fine ;-)

[surlypud]

Are you talking about the HEPA filter just prior to the product (oxygen) tank?

[surlypud]

So, Doug was kind enough to let me bend his ear for a couple of hours yesterday (Thanks Doug!). Turns out that the problem is due to the combination of the Meco Midget torch and an oxygen concentrator. Oxygen concentrators (Doug's DeVilbiss or my Invacare) don't like back pressure and the Meco causes some; likely due to a smaller diameter path through the torch body. This ends up limiting the amount of oxygen you can put through the torch and thus you can't get as hot a flame as you can with a Uniweld 71, J-28, etc.

The Meco Midget is a great torch, just don't use it with a concentrator. Bottled O2 only. Did I miss anything Doug?

[Pritchett]

Glad you got it sorted, even if it means buying a new torch, or scrapping the oxycon...

I had a similar experience with my flashback arrestor now that I think of it. Had to remove the one on the oxygen hose. My j-28 torch has check valves at the handle and I still use the flashback arrestor at my acetylene regulator. with everything working great.

[zetroc]

I've had to bite my tongue for a week now but would like to point out how great the title of this thread is. Bravo.