Propane v.s. Acetylene......

I took a class in tig welding at the collage here and the handed me a ox/acc tourch??
I was told when you can weld with it we will go to tig. I ended up helping the new kids with there tourch welding until the class moved on to tig.

 

Perhaps a bit OT but what was taught 50 years ago about O/A welding is still good. We were given 4"x 4" pieces of 18 Ga. mild steel and practiced "pushing the puddle" , no filler rod involved. When the instructor was satisfied with your progress ,then you got filler rod . This taught the proper way to trim a torch , cordination in forming a puddle and heat regulation. Basic stuff but the basis of it all .

 

Thats how I was originally taught too! And thats how my daughter will be taught when her time comes as well.

 

Hell, that is how we were taught in highschool, back 10 years ago only

I had one of my college teachers ask me if I had a bit of TIG experience based soley on the way my OA welds looked (I have none )

I am also in the catagory that prefers OA for sheetmetal, but I also like to use the MIG for as little as possible. If it can't be stick welded, it can be gas welded

 

What's this I hear about propane/oxygen not being able to gas weld with?...this is news to me since I was just doing that very thing last weekend...am I some sort of sorceror or magician?...I was butt welding 18 gauge sheetmetal with 3/32" copper coated steel filler rod and it turned out like a TIG weld with a 5/8" wide heat spread from the weld seam...

 

WE tried propane for a while but went back to oxy/acetylene for all torch use
propane is cheaper and works ok but acetylene is faster and hotter. acetylene is worth the extra money

 

Originally posted on the Hobart Forum by TRG-42
Pictures added and facts checked by Andrew Booker
When people tell you about how difficult propane is to cut when compared to acetylene they are not really providing you with all the information.

FACT :

• Maximum neutral flame temperature of acetelyne in oxygen is about 5720<SUP>o</SUP>F.
• Maximum neutral flame tempature of propane in oxygen is about 5112<SUP>o</SUP>F.

The difference doesn't really matter as the real concern is for the thermal output ( BTUs ).

FACT :

• BTU's of Acetylene is approximately 1470 btu's per cubic foot.
• BTU's of Propane is approximately 2498 btu's per cubic foot.

So when they say propane gives off less heat it is not entirely correct ( plain wrong actually ). In the welding industry the vast majority of preheating is done with Oxygen / Propane . This is a fact . They don't do it just because it's cheaper but because the available heat from propane is much higher.
FACT : If you look at any torch manufacturers catalog, you will see Propane, Propylene and MAPP heating tips / nozzles of 250,000 btu/hrs to 1,000,000 btu/hrs. But if you look at the Acetylene heating tips / nozzles the maximum you see in the Harris catalog is a relatively small 240,000 btu/hrs, Smith Acetylene heating tip / nozzles are slightly less than 200,000 btu/hrs and Victor is about 300,000 btu/hrs. These are all far less than what they make for Oxygen / Propane use.

<CENTER>Back to the Unfair Comparison</CENTER>For years people professed that Acetylene was better for cutting then Propane . While temperature wise Acetylene is hotter than Propane the fact is that they were using Propane for cutting incorrectly. The mistake they make is that they are cutting with Propane like they would cut with Acetylene. It turns out "where" the heat is in the propane preheat flame is not where it is with Acetylene.
FACT : Propane releases only a small proportion of heat in the inner flame cone ( less than 10% ), so most of the heat in the flame is in located in the outer cone . Acetylene releases almost 40% of its heat in the inner flame cone.

<CENTER>Problem with where the heat is in the flame.</CENTER>

If you cut with acetylene you normally put the tip of the inner flame cone on the metal. If you do the same with propane you will be waiting for a long time. If you raise the torch so that the outer flame cone is used the preheat process is started faster . Is it necessarily as fast a preheat as Acetylene, no but it is nowhere as poor as most people think.
FACT : Just about all industrial plate cutting operations today not using Plasma Cutting Technology ( CNC tables ) are normally done with Oxygen / Propane or Propane derivatives. If you watch these tables cut, it will simply amaze you how quickly they can start a cut on 1" and over plate using the lowly Propane gas.

 

That makes good sense I will give propane another try.

 

good read. my welding gass supplier was just talking about this.

 

I can understand where propane gets a bad rap from, simply by being a different setup and technique than the more common acetylene...for me personally it was not only a matter of expense, but one of safety as well...acetylene is some very dangerous shit, and if you don't believe that to be true then you shouldn't be using it...propane is much more stable, easier to transport, cleaner burning in a small shop and works just as well after teaching yourself how to use it...I will gladly keep using the cutting/welding world's bastard step-child and get the same amount of work done for much less money with a much smaller threat of being blown up...

 

Propane and Acetylene both have their places in the work force. I have a seperate oxy/acetylene setup and a seperate oxy/propane setup in my shop and use both of them. I primarily use the acetylene setup for gas welding and some cutting. I use the propane setup for most cutting and for heating with a rosebud.
One thing to note, is that if you are using or converting over to oxy/propane you have to have the correct tips for your torch setup. Acetylene tips do not work with propane gas.

On a note of safety, I thought it pertinent to add the information below on acetylene gas. It never surprises me on how many of my friends dont have a clue about the equipment that they own and use daily in their shops.

"The unique thing about acetylene is that its combination of 2 carbons to 2 hydrogens is an unstable combination. It only takes 15 psi (pounds per square inch) pressure to make the carbon and the hydrogen explosively disassociate (boom). That is why the red area on the regulator." "Then the question: How come we can't use acetylene above 15 psi when there is 250 psi in the cylinder? This is important. When you knock on the acetylene cylinder and the oxygen cylinder, you'll notice that they sound quite different from each other. The oxygen one is hollow and rings. The acetylene cylinder is filled with what they call "monolithic filler". Used to be sawdust, corncobs, etc. Now is a kind of foamed concrete type material. Into this is added acetone. In the most common size cylinder there is 14 lbs of it added (by weight not by gallon). The acetone absorbs the acetylene into the spaces between its molecules (into its interstices). In this way, the acetylene is stabilized. When we open up the cylinder of acetylene, the acetylene comes out of suspension and is a gas in your hose. You cannot pull more than one-seventh of the volume of an acetylene cylinder in an hour or you will start to take the acetone out too. This is dangerous. You compromise your safety. This can happen if you try to use the cylinder on its side. You can sometimes smell it (acetone is nail-polish remover) and you can see the flame get purplish. If liquid comes out of the torch -stop- and turn it off. When using too large of a torch (a rose-bud), it is easy to pull too much acetylene too fast from the cylinder, especially if you have one of the smaller ones.<O</O

 

Great thread... I like when people talk about this kind of stuff. A couple FYIs...

"MAPP", as it was called using that name, is no more. It was a proprietary gas, and the only company that produced it pulled the plug. There may still be some around, but when it's gone it's gone forever. When you see "MAP" or "MAP/Pro" or other variations of the name, these are just fancy versions of Propylene.

When going from Acetylene to Propane, you may or may not need a different hose... depends on what you have. If you have grade "R" or "RM" (marked on the hose), then ONLY use it with Acetylene... if you have Grade "T", it will work for Propane as well as for Acetylene or any other gas.

Acetylene and Propane regulators usually have exactly the same seats and materials inside... and they share the same CGA connection as well. The differences between them is in the delivery pressure and delivery gauge. This is due to Acetylene's 15 psi max pressure limit (it can be very unstable and dangerous above this pressure), while Propane usually operates at higher pressures. As such, in a pinch, you could use an Acetylene regulator with Propane... but definitely don't use a Propane regulator on Acetylene - because it would be way too easy to over-adjust the delivery pressure and create a potentially dangerous situation.

I would compare the functional difference between Acetylene and Propane similar to the difference between ultra-high octane premium gasoline versus your basic 87 octane "regular". The premium stuff can get things done better, and in a minority of applications is truly necessary, but the regular will save you money, and get all but the most demanding jobs done just fine. By that comparison, other blends like Propylene would be the "medium" stuff... a little better than Propane but not as good as the premium.

For my own personal use, Acetylene scares the crap outta me, and I simply don't do anything that would be significantly better or faster with a hotter flame... so Propane or Propylene work just fine for me.

~Bob

 

Something I haven't heard mentioned is using natural gas. When I was 18 I went to work for a large steel company that manufactured bridge girders and other large steel structural stuff for buildings. We used natural gas / oxygen to cut plate steel up to 6 or more inches thick.

Anyone else used this combination?

 

Hey thanks fellow HAMB-ers...good discussion. I visited the local Jr College and they are killing gas welding off too. Seems like a bummer as so many great hot rods, race cars and aircraft were gas welded...oh well, I'll keep practicing and learning from the seasoned vets as I go. Again, appreciate the info.

 

Glad some guys still "give a shit" and show how to gas weld, I'm a relatively young guy at 36 and I teach welding for a living, I have 20 years experience and have been teaching apprentices for 6. I love gas welding, in Canada, specifically Alberta, the government controls the apprenticeship trades and have been trying to remove the oxy/acytelene portion of apprenticeship training which so far they have been unsuccessful, it is a great way to learn puddle recognition as well as hand skill. Yes it is a lost art and the likely hood of using it "daily" is unlikely but for car guys and sheetmetal it is an invaluable asset, mainly because of the malleability of the deposit.

As far as the question, acytelene is a much better fuel gas for welding than propane, which others have mentioned is not suitable for fusion welding, propane is a good choice for cutting heavy sections because of its high BTU values and is cheap and available everywhere. Mapp gas is not the same as propylene, however they are similiar. Not sure about the U.S but in Canada or parts of, MAPP gas is no longer made or distributed, the new gas that is replacing it is called Flamel85 which uses the same tips as MAPP. We considered switching over from acytelene to Flamel85 at the college I work at but it wasn't cost effective and it is quite finicky to set a torch properly so it wasn't a good choice for training purposes IMO.
Actylene at a neutral flame is 5600 degrees, if you go oxidized it can reach up to 6300, any oxidized flame with acytelene in NOT recommened as the higher O2 values will attack the carbon in steel and make for a very shitty puddle/deposit.

 

i have brazed and welded with propane using the torch tip once in a while. i think one of the main reasons not to do variety of welding with it is trying to replace all your welding tips. do they even make 000 to #9 welding tips for propane? cutting is no big deal i have a propane torch that will cut 5" thick solid round stock- but it takes a while to heat up!

 

I have gas welded for more than 40 years, and have had great service from either gas with the right apparatus.

But nothing cuts like gasoline. On the under 3/4" stuff it is a lot like O/A - once you go to thick material there is no comparison. On 4 inch plate the petrogen unit is more than twice as fast as O/A. You can't weld with it. But it will cut a stack of 3/4 plate 8 pieces thick all at once.

B.

 

I dont think gas welding is outdated. I think most people cant gas weld. My Uncle Wally who was a welder of some skil for many years in Midland Ontario taught me to gas weld with simple verbal instructions. He understood what the secret was and could describe it verbaly. I have had people arguing when looking at my gas welds that they were machine welds not gas welds. A mig is a bag of dung compared to a good gas weld. HOWEVER now that it costs over a hundred dollars a year bottle rent so I can burn about a 1/2 bottle of gas a year I no longer keep tanks here. I go to my pals business and give him a donation each time I need to gas weld. Comparing mig to gas welding is like comparing chop sticks to the clairenet. The mig is was and always will be desiged for people who cant weld. Tig is a more reasonable comparision to gas welding and is probably the ultimate. I use a scratch tig when I weld steel with a tig (about $120 attachment to a normal DC welder )although I have an ancient HF rig donated by an old friend for aluminum. The process is very similar to gas welding. I tried welding with propane but was not satisified with the results. OXY/Acet works just fine . Just the bottle rent thing (Called "welding bottle marriage" up here) is the drawback.
Don

 

I'm waiting for Hank Hill (Assistant Manager - Strickland Propane) to chime in on this one.

 

if not Hank, maybe his son Bobby will chime in.

 

Most of the scrappers around here use propane because it is cheaper and the quality of the cut isn't an issue as long the chunk of metal is cut.

As for what I use on the sheet metal of my truck I'll most likely use the mig to get it all fitted together and weld up the areas that have to be finished perfectly with gas. I'm a lot better gas welder than I am a mig welder when it comes to sheet metal.