acetylene vs propane

[Doug Fattic]

I thought some information about the differences between using oxyacetylene or oxygen/propane might be interesting for those wanting to get their own equipment to make frames. I've used both. I learned how to hearth braze (a giant natural gas flame heating up a whole joint surrounding by firebricks) when I apprenticed in England as well as braze with brass using an oxyacetylene torch. We set up our framebuilding shop in Ukraine (where we make bicycles for pastors) with an oxygen/propane unit. I use oxyacetylene in my shop in Niles, MI and have recently set up to braze with propane as well. It is possible that some might like to use propane because it can be much easier to buy and transport and possibly be cheaper. Sometimes city ordinances prevent its use in residential areas (particularly in big cities) and sometimes welding supply stores won't sell bottled gases to non businesses or let you leave with one of their/your bottles unless it is carried certain ways. And insurance policies may limit where acetylene tanks can be located. Propane is less regulated because of its common home use in grills, etc. Welding stores can be ignored entirely if an oxygen concentrator is used instead of bottled oxygen. Those are the machines that keep grandma alive when her lungs aren't working well any more. Many of my framebuilding class students find using propane a better option. Here are some of my observations between the 2 types of fuel.

A propane torch is slightly more fussy to light than acetylene but has a cleaner flame. It doesn't rain soot if it isn't turned up rapidly enough. A propane flame wants to detach itself off of the torch tip. Once oxygen is added it can be turned up more. It will blow itself out easily if the adjusting knobs are turned slightly too much. Propane doesn't have distinctive visible inner cones like acetylene to assist in adjusting to a neutral flame. Its also noisier. It is necessary to go up a tip size or two to get the same heat volume. For example I commonly use a Smith AW205 tip on my AW1A torch handle. In Ukraine I use the AW207 with propane.

A propane flame isn't quite as hot and the bigger tip required to put out the same amount of heat isn't quite as sharp. This isn't usually a difficulty when silver brazing lugs. And could actually be an advantage for beginners because it is slower to heat up giving them more time to analyze and adjust. However I feel it makes fillet brazing a little more challenging. That said I fillet braze joints in Ukraine with propane without any difficulty. It is easy for me to adjust to using either one.

While most oxyacetylene equipment will work with propane, some adjustments will make it work better. For starters, Victor propane #-TEN torch tips have a slight recess at the end of the tip hole to help keep the flame attached. They screw onto the end of a UN-J mixer/elbow that attaches to a J-28 torch handle. Smith's NE series of propane tips designed to screw onto the end of their propane only AT61 mixer/elbow (that go to their AW1A handle) are too big for general framebuilding use. They don't have a recess in their tip. The Victor UN-J unit can also be used with acetylene with their TE series of tips. The T series of rubber hoses are recommend for propane. Standard welding hoses won't last as long.

How to use an oxygen concentrator instead of bottled oxygen is a separate subject.

[Straz]

Great post. I am very interested in hearing about using an oxygen concentrator.

[devlin]

I am looking at getting a propane torch rather than acet. for the reasons you mentioned. ie. transport, storage and availability. Thanks for highlighting the difference in use though, some great info there.

I have one question. Would the town gas supply to our house that we use for the stove be suitable for use. Is the supply pressure the thing to look at here?Obviously you lose the portable nature of having bottles but I would probably only need that feature once every couple of years. So no real loss.

With an oxygen concentrator (depending on cost and practical use) I could do away with bottles all together.

[devlin]

Just went and did the google thing. Haven't answered the town gas supply thing but found plenty on the Oxygen concentrators.

[Honus]

I have one question. Would the town gas supply to our house that we use for the stove be suitable for use. Is the supply pressure the thing to look at here?Obviously you lose the portable nature of having bottles but I would probably only need that feature once every couple of years. So no real loss.

With an oxygen concentrator (depending on cost and practical use) I could do away with bottles all together.

At my work (jewelry making) we use oxygen tanks along with natural gas that is piped into the building (at around 5psi) but it's not as hot as propane. We have a propane/oxy setup for casting metals because of this. Natural gas is cleaner though. A lot of mall jewelry stores use oxygen concentrators and natural gas because they aren't allowed to have indoor tanks. Many city ordinances also do not allow propane tanks to be stored indoors- be sure to check with a local fire department to make sure it will pass inspection. When looking for an oxygen concentrator be sure to check out jewelry stores that are going out of business. Ditto for tanks.

[devlin]

Tanks (pun inteneded) Honus

[dsaul]

If anyone was looking for the Uniweld 71 torch, Amazon has it for $35 with free shipping.

Ameriflame MD71TH 6-Inch Light Duty Welding Handle for General Purpose Heating, Brazing, Welding and Other Flame Processes - Amazon.com

[Doug Fattic]

Oxygen generators come in 5, 10, 15 liter per minute outputs. They have replaced small oxygen tanks used to assist breathing for those with health problems. They take the other stuff out of the air and deliver almost pure oxygen. There are federal regulations governing the sale or rental of this kind of medical equipment – which is often paid for by insurance. You have to have a doctor's prescription to get one from a medical supply place where they are really expensive. However there are places that refurbish and sell them for non-medical use – typically lampworking (melting and shaping glass). Occasionally a spouse will sell them after the partner is gone in the classifieds or on craigslist. In my local South Bend Tribune there was one for $200 a few weeks ago although I didn't call soon enough. I bought a reconditioned Devilbis 5 liter one outright from a company that refurbishes them in PA for $350 + $30 shipping. It has a 36 month warranty. They are designed to run something like 10,000 hours before needing to be sent back to the factory for reconditioning again. The online Jewelry supply company RioGrande sells them new for $425. Because they don't require a regulator or be refilled, getting one might be a financially attractive and/or more convenient option.

I put one of my Victor acetylene regulators with 510 fittings directly on my propane tank. Regulators for the smallest tanks have a different fitting. The barbed oxygen outlet on my concentrator (that accepts clear plastic tubes) can be unscrewed and a welding hose with a "B" fitting can be screwed directly onto the outlet. You don't need an oxygen regulator. It is necessary to let the concentrator run a bit (2 or 3 minutes) before it has a steady flow rate. Otherwise its initial bursts of oxygen will blow out the flame. If you don't have the oxygen knob on the torch open when it is running, it will beep a warning. There is a dial on the unit that regulates the flow from 0 to 5 lpm (liters per minute). This needs to be adjusted to the tip size. I typically use Victor 2-TEN to 4-TEN tips. Conveniently a size 2 tip seems to require about a 2 lpm flow rate and a 4 tip 4 lpm (give or take). If the flow rate isn't right, it will blow out the flame. There certainly is a much longer learning curve to getting the settings right.

They create a background noise similar to an inverter welder. They aren't noisy but aren't quiet either. And of course a propane flame is noisier than an acetylene one too. This combination shouldn't be strong enough to be a deal breaker for anyone but one should be aware and prepared for this additional noise in case they are used to enjoying the quiet of oxyacetylene.

[echelon_john]

Look at MAPP/Chemtane as well.

[Greensabbath]

Thanks for posting this. I am hoping to get a oxy-propane brazing rig for Christmas and I am still trying to figure out what to get. If the Smith NE tips are too big then which tips would you recommend when going the Smith route? Or should I just go the victor route with the TEN tips?

[Doug Fattic]

Thanks for posting this. I am hoping to get a oxy-propane brazing rig for Christmas and I am still trying to figure out what to get. If the Smith NE tips are too big then which tips would you recommend when going the Smith route? Or should I just go the victor route with the TEN tips?

Smith doesn't recess their tips like Victor does. I use the standard Smith AW207 tip on a AW1A torch handle in Ukraine. It works fine but not quite as well as the Victor TEN tips on a UN-J mixer. The Victor controlled flame doesn't detach as easily and seems to have a sharper point. Smith used to make mixer/tips specific for propane in their AW line. They were the AW40# series (the # representing the number of a specific sized orifice – for example AW407. I would presume that to be the same size orifice as the AW207). I don't think they make them any more just like they quit making the AW204 tip assuming either the AW203 or AW205 was close enough.

If I didn't have a torch handle already and was on somewhat of a budget, I'd get the Uniweld 71. It is similar to the Victor J-28 and accepts the same mixers. It has a slightly larger diameter and longer handle with bigger aluminum knobs. It is slightly lighter. On my Park scale the Uniweld handle weighed 85 grams by itself and the Victor weighed 124. I can actually tell the difference in my hand although it really doesn't matter. It will cost under $100 if you look around online and the J-28 a bit more than $150.

It is possible to buy clones of the Victor UN-J mixer and TEN tips for less money too. However they don't seem to be quite as well made. For example the Gentec 883-3 tip which is equal to the Victor 3-TEN tip does not have a square inside shoulder where the thread-on part is reduced in size to the orifice. It is domed a bit like the shape of the end of a drill bit. It doesn't seem like much of a difference but on a couple of my Gentec tips, flame would sometimes come out the back of the tip. I found that unsettling.

Uniweld says its 17 line of tips for the 71 handle work with all fuels. I've tried the size 2 and it did work with both propane and acetylene but of course all acetylene tips seem to work with propane. You just have to fuss with the settings more carefully or the flame will blow out. In your letter to Santa if you've been nice, you might want to ask him for some light hoses too. Either the Smith Kevlar ones or the slightly heavier and tougher ones made by TM technologies.

[Alistair]

Look at MAPP/Chemtane as well.

I'm pretty sure MAPP is dicontinued, but Chemtane is available. The big gas supply houses (Praxair, AirGas etc.) often have their own house brand of Propylene with names like AgFuel, FG-2, FlameAll etc.

Sometimes they're just straight Propylene, but sometimes they're souped up with some additives. I use Acetylene, but I think the alternatives are interesting to look at.

Alistair.

[mattsummers]

Propane pressure should stay pretty constant as long as any liquid remains in the tank. The vapor pressure of propane varies with ambient temperature.

http://docs.engineeringtoolbox.com/d...r_pressure.pdf

Once the liquid propane is exhausted, the pressure will drop quickly. This is why LPG is sold by weight, and not by pressure like compressed gasses like argon or helium.

That being said, I'm looking to switch to oxy/propane for brazing myself...(don't like the sooty acetylene startups in the shed)

[veryredbike]

I'm glad everything is working out with this unit, mine should come today! How did you hook up the hose/regulator to the unit? My flashback arrestors won't get here until next week otherwise I'd be firing up my unit today as well.

Please forgive errors or brevity. On a phone. On vacation.

By unit do you mean the oxycon or propane? For propane I made an adaptor: disposable attachment to 1/4 npt, elbow, valve rated for over 200psi on gas for emergency shut off, female cga 510 (I think, no full sized Internet to confirm). Used pipe dope rated for high pressure and propane, cured it to manufacturer suggested time.

For oxygen, no regulator. Used a tube used to couple medical oxygen devices and a barb to male b hose adaptor.

For folks still buying their oxycon.... I'd see if you can find something that does more than 5psi if you want to use a flashback arrestor, it won't work with 5. Remember that flow and pressure are related but different. I think the devilbliss 5lpm use 7 psi.. And it sounds like Doug got that working?

[veryredbike]

Alrighty, did a little test-brazing today. Got better at keeping the flame attached. This cheapo #2 might just be fine after all (it's oxy/fuel rated but not recessed). Also did some tests to get used to my new safety glasses, which are a bit darker than the ones I'm used to.

I'm still having trouble identifying neutral for brazing. I get to the point where the whole thing is blue, but the inner cone is a bit soft (calling this point A)... then if I add oxygen to sharpen that, it gets a little bluer and noisier (it's basically silent before)... but still quieter than what I'm used to (calling this point B). After that it gets louder and I see a more pronounced blue shift (point C). I'm guessing point A for fillet, point B for lugs, but I'm not sure if I'm shifting things over a bit and it should be B and C and I'm just being cautious about how much blue constitutes bluer ;-) Anyone run across a good video of this for propane? I haven't found a really clear one yet.

Thanks again for the thread, having my own torch to play with is pretty awesome. I've got some paid training and a class to teach coming up that'll pay for a few more practice lugs, and some e-richie tubing to go with the nice Llewellyn lugs I have sitting next to my couch in a box. Pretty excited to make a bike with this thing.

On lifespan of the little cylinders... still going strong, but I did enough practice today that I don't think it'll be a problem. Even if it goes out soon, I think I could do a main triangle with one bottle... which is fine at my slow rate of work.

[Doug Fattic]

Veryredbike, I went out to the shop tonight to light up the propane torch to see if I could provide any additional information. I carefully watched the flame change color from greenish to blueish as I added oxygen. The right blend of propane and oxygen was just at the color shift when the green became blue. Of course as I continued to add more oxygen it got even bluer. I measured the inner cone and it was 16mm at that adjustment with a Victor #2 tip. Of course in addition to the balance between the 2 gasses you have to have the right volume. That depends on the thickness of material being brazed and I go by the sound of the flame. It is a bit loader than the gentle hissing of an oxyacetylene frame.

For learning purposes, I wouldn't use too dark of a lens. If one is brazing all day long than greater precautions are necessary but one has to see what is actually happening at the joint in order to catch on what to do. For occasional use I think good sunglasses will work. Eventually you can go to a number 3 lenses when your motions become more automatic.

[veryredbike]

Thanks Doug! Great advice all around! I'll play with it more this weekend.

[Jim Gourgoutis]

Is there any need for a reg with two gauges? The vapor pressure in the tank shouldn't swing much until it's just shy of empty.

Some of the lamp worker folks use a simple pancake-style regulator without any gauges.

[Jim Gourgoutis]

No there isn't. Unlike acetylene, tank pressure does not indicate how much is left. In our frame shop in Ukraine we use some kind of cheap propane regulator that only has one gauge. There is a gauge for BBQ units I bought at Lowe's that I stuck in between the tank and the regulator that tells me how much propane i have left.

Doug, is this the gauge you got?

http://www.lowes.com/pd_231786-66482-80064L_4294703218__?productId=3352972&Ns=p_product _qty_sales_dollar%7C1&pl=1&currentURL=%3FNs%3Dp_pr oduct_qty_sales_dollar%7C1&facetInfo=

[Ryan Christbaum]

Thanks for all of this information, Doug. Very useful.

Because of this thread, I bought a propane elbow and some tips for my Smith A1WA. I chuckle to myself thinking of the run on used oxygen concentrators by frame builders, but it sure makes sense from a safety and convenience point. Just to be safe, I decided to buy the proper rated hose for all fuels, so I got a length of the regular rubber type and a kevlar section. If feels rather flimsy, but the kevlar hose is awesome at the torch end and I highly recommend it. Unfortunately (but not unexpectedly), my attempt to practice a joint with propane felt like trying to write left-handed. The fillet was okay and seems plenty solid, but didn't look as nice as I can normally pull off w/ acetylene.

I need to re-read this thread to fine-tune the flame I'm using (and practice), but I didn't really have much trouble with lighting the flame or keeping it lit. If nothing else, price and convenience of LP makes me want to pursue this as an alternative to acetylene. The addition of the concentrator being useful for either fuel does seem like a smart alternative to a high-pressure bottle, so maybe in the near future.