Converting from acetylene to propane

[charlz]

In high school I spent a summer cutting salvage steel (railroad cars). We used propane since it was so much cheaper and all we were doing was cutting. I still use it today for heating for bending and the like as that takes a lot of gas and propane is cheaper.

While the flame temperature is lower with propane if you are using a propane cutting tip you are actually getting more BTU's so it heats faster.

 

[Taylortractornut]

I dont use propane, unless I run out of acetylene in the middle of the weekend or my supplier is out. It seems to use alot more oxgen than when using acetylene. I worked for a fella once that built log trailers and used it because it was cheaper to run but while using it he would go through at least 2 bottles a day of oxygen. The tips were easy to clean just take off the outer shell and clean the oriface and then wire wheel the flutes on the inner part. I did really enjoy using it outside when lighting it the wind could blow the fuel only flame out. I liked it alot when cutting doble plated parts like the tops of bush hogs that had been double plated and cutting out the fifth wheel plates and king pins on the log trailers it seemd to excaell in that. When we built a 5th wheel lowboy and it came time tobend the gooseneck plates over he always had a bottle of acetylene we used. Ive used it in my pattern burner on some plate for a brush rake and really didnt like it it does cut as good as AO but I couldnt save much on my fuel bill doin so with the oxygen cunsumtion but then again I was cutting 2.5 inch plate.

 

[slowzuki]

The think with propane is it uses the exact same amount of oxygen to cut, but the preheat uses more oxygen. If you added a preheat shutoff to your machine torch you could save a lot of oxygen and propane.

For me the aetylene cylinders and refills are just too expensive for my infrequent use. My oxygen tank is 40 or 50$ a year rental and 30$ a fill. The acetylene was 80$ a year and who knows how much a fill.

So, to make up for that savings I got a plasma cutter haha.

 

[JB4310]

I only go thru a couple of bottles a year but I remember saying to counter guy after looking at the bill "the oxygen costs more than the acetylene?" don't remember what the answer was, might have been misinterpreting the bill.

I switched to the smaller bottles (about 2' tall) from the larger ones, just to make it easier to pick up the whole cart and put on the truck.
Rental is the same between the large and small but if you had to pay for them, the larger bottle is pretty expensive, $300.+ maybe.

I'll stick to the acetylene, but it's good to know propane can keep substituted.

JB.

 

[Eagleview]

The nut on the Acetylene gauge needs to be changed over for a Propane nut . A Propane nut will screw into an Acetylene bottle but an Acetylene nut wont screw into a Propane bottle .

 

[Egon]

Just a few more thoughts.

Propane is very dangerous unless proper hoses are used because propane will deteriorate hose and leak out. It could cause a fire.

Propane cutting takes more oxygen since more fuel must be consumed to deliver the same number of BTU's. While it may be more cost effective in the hands of a skilled operator propane cutting is more costly to an unskilled amateurs. Of course were all good!

Once the steel in the kerf is liquefied and the secondary oxygen is discharged Thru the center hole of the tip the molten steel itself becomes the heat generating fuel for the cut. A skilled operator can turn off the preheat fuel and maintain the cut. Thats why steel can be cut with propane but can't be welded using propane.

 

[DanD78]

I have an adapter to go from a propane thread to acetylene thread. I have had the same 50' hose for 25+ years. They must be good for propane because they don't leak and are still very flexible. I use a Harris cutting torch with propane tips for different thickness of steel to be cut. Propane also works good with my Harris rose bud heater that is meant for propane. My Victor rose bud for acetylene will not stay lit and back fires bad.

Be sure to use check valves at the torch and the regulator. I have never had a hose or regulator blow up but have heard storied and seen pictures. Not good

Dan

 

[Egon]

My Victor rose bud for acetylene will not stay lit and back fires bad.

Is the supply adequate?

They must be good for propane because they don't leak and are still very flexible

Does the manufacturer recommend the hose for Propane?

 

[xlr82v2]

I've been using propane in my oxy-fuel rig for a few years now... here's my take on propane as a fuel. This is a cut-and paste from a post I made a while back... you can find that thread here.


Here's my take on Propane...

You can use the same regulator with propane as acetylene... no changes needed.

If using propane, you should get Grade "T" hose... which is for all fuels. Grade "R" hose is for Acetylene only. Why? I don't know... probably some component of the Grade "R" hose degrades with exposure to the petroleum based hydrocarbon fuels. Get the Grade "T" hose. It's a little more expensive, but what you will save by using propane will more than make up for it.

You will need special propane tips to use with your torch. Not a big deal, just go to a welding supply shop, and get them, or have them order them for you if they don't have them in stock. Tractor Supply, Rural King, etc. might have the tips you need also, depending on what brand of torch you have. You can use acetylene tips with propane, in a pinch... but it is REALLY HARD to get the torch lit. If there is any breeze at all, forget it. But it can be done. Get the propane tips and save yourself the aggravation. Trust me.

Opponents of propane will tell you that you will use more oxygen with propane than acetylene... and technically, they're right. Propane requires more oxygen to burn than acetylene (2.5 to 1 for acetylene vs. 5 to 1 for propane). But, in practice, 95% of your oxygen is used in actual CUTTING (the center hole in the tip)... which is the same for either Propane or Acetylene. In actual use, I think the difference is negligible. The preheat flame doesn't use that much fuel and oxygen. What ever amount more that you will use in preheat is more than made up for by the difference in cost of the fuels. Check into the lease cost of an acetylene cylinder (or even purchase cost for a smaller cylinder) and compare that to what it costs to fill a 20lb propane tank... That difference will buy a LOT of oxygen.

Opponents of propane will tell you that propane does not burn as hot as acetylene... and they are right. Neutral flame temp of Oxy/Acetylene is 5589 degF, and 4579 degF for Oxy/Propane. What they won't tell you is that Propane puts out nearly 59% more BTU's (1470 BTU's/cubic foot for acetylene, 2498 BTU's/ft3 for Propane) than acetylene, making it a superior fuel for heating/bending jobs.

Opponents of propane will also tell you that it takes longer to start a cut using propane. They are correct, when you use the same technique as you do with acetylene. What most people that don't like propane don't know is that the hottest part of the propane flame is NOT at the tips of the flame cones like it is with acetylene, but about an inch down, in the feather portion of the flame. If you start your preheat with your torch about 1 inch or so above your workpiece so that the edge to be cut is in the hottest portion of the flame (about 1 inch from the flame cones), the greater BTU output of propane makes the preheat time very close to that of acetylene. Once your metal is at temperature, you then lower the torch to the flame cone tips, and cut just as you would with acetylene. So, you do have to adjust your technique just a bit when using propane. Not a big deal, I don't think. I was cutting some 1/2" steel plate and I could start a cut on cold steel with about a 3-4 second preheat with proper technique. That's pretty dang close to acetylene.

Opponents of propane will tell you that propane doesn't cut as smooth as acetylene. I don't know about that... that's really a judgement call when using a handheld torch, and is influenced as much by operator and his prejudices/preferences as it is anything else. I've seen machine cut steel that was cut with propane, and it looked like it was cut with a plasma. Honestly, I dont' think the fuel makes any difference in this area.

You CAN braze with propane. Propane works very nicely for brazing. You cannot WELD with propane. The combustion products of propane work to contaminate the weld puddle, giving a poor weld. But, if you're not gas welding, it doesn't matter.

So... in a nutshell,

Propane is not as "hot" as acetylene... but puts out almost 59% more BTU's... making it better for heating/bending steel. (Temperature and BTU's are not the same thing)

Propane requires a slightly different preheat technique than acetylene... but once this is learned, the difference between the fuels greatly diminishes.

Propane is MUCH less expensive than acetylene, and much more readily available. Chances are, if you run out of acetylene on a Saturday afternoon/Sunday project, you're out of luck until Monday. With propane, you can borrow the tank off the gas grill, or go down to the supermarket and exchange your tank and you're back in business. Mighty convenient.

A 20lb tank of propane lasts forever. I don't do a tremendous amount of cutting, but I do go through about 3-4 size "M" bottles (about 140CF, IIRC) of Oxygen per year on average. I've had my own Oxy/Propane setup for 3 years now, and I'm still on my first tank of Propane. That's cheap cutting.

So, is Propane Superior to Acetylene? No. But, it does a better job in heating/bending operations because of its greater BTU output (takes less gas to heat the metal to the same temperature) than acetylene. It is not quite as hot as acetylene, and the heat is not quite as concentrated as acetylene. But, with a modification in preheat technique, these differences can be negated. You can braze with propane, but you can't weld with it. Not a real problem these days.

All that said, I really like propane. It works. It's just different than acetylene, and that's what most people that don't like it, don't like.

 

[Egon]

If using propane, you should get Grade "T" hose... which is for all fuels. Grade "R" hose is for Acetylene only

Thanks