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PTSideshow
06-22-2011, 11:17 PM
While I was picking up some back order items at my Local Airgas I was informed that the price increase for acetylene has arrived they have double approximately. for all sizes and they are going to have a limited number of assorted sized cylinders available.

quasi
06-22-2011, 11:32 PM
switch to propane?

macona
06-23-2011, 01:18 AM
My dad uses something called chemtane. It propane with an added chemical or two. Hot! Hotter than mapp.

PTSideshow
06-23-2011, 05:42 AM
switch to propane?
I have but others may not have, I know the guy that was in there when I was and wanted a refill was in a totally unaware state. Even with the printed price list on the counter.

.RC.
06-23-2011, 05:47 AM
I made the switch to lpg (propane) and never looked back...

In todays world with mig and plasma, oxy/acetylene is no longer as important as it once was..

GKman
06-23-2011, 07:52 AM
What's the procedure and limitations switching to propane?

sasquatch
06-23-2011, 08:13 AM
I switched to propane quite some time ago, at least 10 years or so.

I,m no expert just a hobby guy,, but the only switch i made was to purchase a new tip for cutting with propane.

Propane is not as hot taking a bit longer, which worked fine with me as i wasn,t into any heavy equipment repairs or things like that.

I did a lot of brazing,, and it worked fine for that.

Now in Ontario there is an "ECO" tax on any bottled gas including oxygen which seems bizzare for oxygen.

GNO
06-23-2011, 08:48 AM
not so bizzare, rub 1st & 2nd fingers togetter w/ thumb [universal sign for money]

sasquatch
06-23-2011, 08:55 AM
Re: another money grab: "EXACTLY that is most peoples thought!!":(

Evan
06-23-2011, 09:06 AM
Aetylene hasn't increased here. They have put a small extra "handling" charge on the tanks my wife sells which is around $4 per bottle. The supplier across the street hasn't increased prices at all. All of the actylene here is refilled in Washington state.


The limitations of all other subtitutes for acetylene are flame temperature in the central flame as well as the amount of heat in the central flame. Propane and similar fuels burn at lower temperatures but more importantly the amount of heat in the central flame is much lower. Most of the heat with propane is in the outer envelope which makes it unsuitable for welding.

The other issue is that the amount of oxygen used is much greater with propane and other substitute gasses. With MAP, Propylene and Propane you will use about three tanks of oxygen for every one tank you use with acetylene. Note: It doesn't make that much difference for cutting since when cutting you are burning with oxygen anyway. But for heating and brazing it will actually cost more than using acetylene.

ANother consideration is that Acetylene has a far wider range of flammable gas ratio at which it will burn. It makes it much easier to maintain a stable flame with acetylene.

sasquatch
06-23-2011, 09:15 AM
Only speaking from my experiences which don,t amount to a pinch of fly sh*t, but have to disagree about using up more oxygen using propane to braze,,, i saw no difference at all.
Had nice consistent flame.

Evan
06-23-2011, 09:32 AM
It MUST use more oxygen. It isn't something that you can adjust by changing settings. Acetylene uses 1.4 parts oxy to 1 part acetylene to produce a neutral flame. Propane uses 4.5 parts oxy to 1 part propane. It's chemistry that cannot be changed.

justanengineer
06-23-2011, 09:44 AM
I cant speak about using propane, never have but it sounds interesting, but I would recommend the OP look into a new gas supplier. My father in NY got acetylene a few weeks ago and there was no increase. His supplier told me a few months back when I ordered welding lenses and inquired about it, that there would be no price increases and it was all hype. A month or so ago I asked the local delivery driver about a price increase, and got teased about being gullible. My plant hasnt seen an increase in price either, so Im thinking its simple price gouging in certain areas.

Willy
06-23-2011, 11:48 AM
I have been using oxy/propane for cutting and brazing for well over thirty years and have no issues with the process whatsoever. It has saved me a lot of money and of course the freedom of not being tied to a supplier for a higher cost fuel gas.
Besides, who doesn't have a few extra BBQ tanks kicking around at any given time?

I'm fond of oxy/acetylene welding though, as my not having a tig machine it's as close as I've come to the concept.
This is one process that I can no longer enjoy with oxy/propane. Due to the characteristics of the oxy/propane combustion process it does not produce the needed carbon dioxide shielding gas required for the welding of steel.
Just a heads up for those that may expect to use oxy/propane, or other fuel gases in lieu of acetylene.

Ray C
06-23-2011, 12:50 PM
FWIW: I live in the Annapolis/Baltimore/DC area and have not been able to get acetylene at all for the past 4-5 months... I am too small of a customer (hobbyist) and they only do partial refill orders for large customers. -Same story after visiting all the major refill depots in this area...

Some are willing to sell me propylene but I'm not familiar with that and havent had time to figure it out.

Can anyone comment on propylene as a substitute?

Black_Moons
06-23-2011, 04:23 PM
It MUST use more oxygen. It isn't something that you can adjust by changing settings. Acetylene uses 1.4 parts oxy to 1 part acetylene to produce a neutral flame. Propane uses 4.5 parts oxy to 1 part propane. It's chemistry that cannot be changed.

Should'nt it be using a lot less propane to produce an equivilent amount of heat (Btus) however since its combusting with oxygen that many more times to turn into CO2/H2O?

I mean sure, propane is not as 'hot', But I would suspect the oxygen usage per BTU output to be rather consistant.

I guess BTU output per oxygen depends mainly on the reactions involved. ie what produces what amount of heat for a given amount of oxygen.
C+O =CO
CO+O=CO2
H2+O=H2O

I believe are the 3 main reactions in acetylene and propane.. Just the question is how many BTU's does each reaction produce, And how many times does each reaction occure in an acetylene flame verus a propane flame before everything is CO2 or H2O. Devide that by number of oxygen consumed, And you get the BTU per oxygen! :)

<Correct me if im wrong. My chemistry is weak but I would love to understand more>

Black_Moons
06-23-2011, 04:26 PM
FWIW: I live in the Annapolis/Baltimore/DC area and have not been able to get acetylene at all for the past 4-5 months... I am too small of a customer (hobbyist) and they only do partial refill orders for large customers. -Same story after visiting all the major refill depots in this area...

Some are willing to sell me propylene but I'm not familiar with that and havent had time to figure it out.

Can anyone comment on propylene as a substitute?

****ty. Never used propylene but this 'partial refill' seems kinda odd.

Can't you ask for a full tank refill? Around here they won't even refill tanks. they can't, Nearest place to refill em is like a province away. What they do is exchange tanks. Don't think you'd get any discount for bringing back a half full tank.

bob_s
06-23-2011, 04:39 PM
Should'nt it be using a lot less propane to produce an equivilent amount of heat (Btus) however since its combusting with oxygen that many more times to turn into CO2/H2O?
...
<Correct me if im wrong. My chemistry is weak but I would love to understand more>

You are RIGHT!

By volume it takes less propane to generate the same amount of heat as acetylene. The heat of combustion, for acetylene and propane, is almost identical on a unit mass basis (21.5 vs 21.7 BTU/lb respectively).

Reactions
Acetylene

10 C2H2 + 25 O2 -->> 20 CO2 + 10 H2O

Propane
5 C3H8 + 25 O2 -->> 15 CO2 + 20 H2O

sasquatch
06-23-2011, 04:55 PM
Re: Using more oxygen with propane,, today i asked my buddy at the welding shop he owns,,, and he said YES it would require more oxygen but mainly in cutting. Just brazing, it would be minimal so Evan is correct on that one.

Interesting discussion,,,,,, and yes he hasn,t a shortage here much, although he is limited to any large acetylene order.
So it appears to be different in different areas.

Black_Moons
06-23-2011, 05:28 PM
You are RIGHT!

By volume it takes less propane to generate the same amount of heat as acetylene. The heat of combustion, for acetylene and propane, is almost identical on a unit mass basis (21.5 vs 21.7 BTU/lb respectively).

Reactions
Acetylene

10 C2H2 + 25 O2 -->> 20 CO2 + 10 H2O

Propane
5 C3H8 + 25 O2 -->> 15 CO2 + 20 H2O

Ok awsome :)

But still, the question remains about actual heat production per oxygen, Because all these chemicals undergo multiple reactions before they hit CO2/H2O, One might be using its oxygen more efficently (Undergoing more and stronger exothermic reactions per atom of oxygen)

Id also like to note that because they result in diffrent quanitys of H2O and CO2, just that reaction alone will cause one to use more or less oxygen per BTU output, since I would assume CO2 and H2O reactions don't output the same BTU per oxygen. Unfortualy my chemistry is weak enough that I don't know how to get all the reactions and count thier BTU outputs.

PS: I think you might of halfed your input volume of oxygen accidently?
20 CO2 + 10 H2O requires 50 oxygen, 20 carbons and 20 hydrogens (10 C2H2's)

I also find it intresting that while propane produces very similar amount of CO2, Its produces twice as much water. Hence I guess acetylene is more of a dry flame. I don't think H2O is a benifical compound to have in your welds/brazes/solders/base metals.

Ray C
06-23-2011, 06:11 PM
****ty. Never used propylene but this 'partial refill' seems kinda odd.

Can't you ask for a full tank refill? Around here they won't even refill tanks. they can't, Nearest place to refill em is like a province away. What they do is exchange tanks. Don't think you'd get any discount for bringing back a half full tank.

Sorry, I wasn't clear... Depending on what depot you visit, they'll either test/refill your existing tank or do an exchange. Smaller depots do exchanges.

let's say you wanted 3 tanks refilled (and/or exchanged). They might accommodate 1 or 2 tanks but only if you're a regular, high-volume customer. There are at least 5 large filling centers in this area owned by 3 different companies all within 30 miles of my location. There's another 8 or 10 if you go out another 10-15 miles. My tanks are only registered with one the companies but all of them are telling the same story. Tried to register with the other companies and got turned away -but they did offer to set me up with propylene...

rws
06-23-2011, 06:20 PM
I use propane as a hobbyist, and it works fine for me. I don't get inot cutting anything thicker than maybe 1/2". Different cutting tips, and good to go.

I work construction, and we had a large demo job where we hired a demo contractor. They used propane instead of acetylene. They used large air tanks and 100# propane tanks. Said it was more economical.

Evan
06-23-2011, 07:20 PM
Should'nt it be using a lot less propane to produce an equivilent amount of heat (Btus) however since its combusting with oxygen that many more times to turn into CO2/H2O?



Yes, propane generates more BTUs per unit volume than acytelene. The problem is that the heat is in the wrong part of the flame for certain operations. If you do a lot of short cutting and piercing jobs you will spend a lot longer during preheat to the ignition temperature because all that extra heat is in the outside part of the flame. On long cuts it makes little difference because the oxygen is combusting the iron. Acetylene concentrates the heat in the inner cone and has almost twice as much heat there compared to propane as well as much higher temperature. That also applies to welding and brazing. For general preheating propane is cheaper.

BTW, if you do a LOT of cutting, heating etc then the cheapest way to go is to use liquid oxygen. It is much cheaper than compressed oxygen. That is what the local job shop uses in the fabrication shop.

CCWKen
06-23-2011, 08:51 PM
Liquid oxygen? You'd have the "suits" showing up at your house down here. :D

Evan
06-23-2011, 09:43 PM
They have a big stainless steel pressure dewar about the size of two 55 gallon drums stacked, with a built in radiator to gassify the LO2. It has a manifold to run a dozen torches at once.

PTSideshow
06-23-2011, 09:54 PM
That is what a lot of the glass bead shops around here that teach classes, use a dewar and manifold set up. To supply the glass torches for the student stations.
I can only add that for cutting that after adjusting for a longer preheat time it works about the same other than the travel rate is slightly slower. I tended to out run the preheat for the first two sections of I beam that I cut.

For the $20.00 investment for the propane tip It will be a good deal for all the items that the Hypthrem 600 won't sever well!

J.Ramsey
06-23-2011, 10:01 PM
Used both in the the last 35+ years and if was I stuck with only Propane as a fuel gas I'd quit or use an Axe as far as cutting is concerned.

lazlo
06-23-2011, 10:04 PM
BTW, if you do a LOT of cutting, heating etc then the cheapest way to go is to use liquid oxygen. It is much cheaper than compressed oxygen. That is what the local job shop uses in the fabrication shop.

The ACC forge/welding shop has oxy/acetylene plumbed everywhere (which is really nice!), and the oxygen is provided by a large LO2 dewar.

They have the dewar and the gas bottles isolated in a separate room with minimum safe distance between oxygen and acetylene.

Willy
06-23-2011, 11:56 PM
Used both in the the last 35+ years and if was I stuck with only Propane as a fuel gas I'd quit or use an Axe as far as cutting is concerned.

Can't understand this, there is obviously something wrong here.
What parameters are you using for material size being cut?
Travel speed, standoff from material being cut, tip size, gas pressures, etc.?

Granted oxy/acetylene is a little faster, and usually a little more clean in the cut, but not by much. I regularly cut 1/4-7/8 in. material and the cuts are very clean and decently fast.
Don't rely on the same techniques and procedures you are accustomed to using with oxy/acetylene. There is definitely a learning curve if you are not used to the characteristics of propane as a fuel gas. It's not wrong, just different.
Try some different settings.

A link to a short video of a oxy/propane cut in a section of heavy steel:

http://www.youtube.com/watch?v=Zy3g4-D1ZeA&feature=related

Although the video shows a 3 line, 3 regulator industrial unit, there's every right to expect the same quality of cuts in lighter gauge material with a conventional, medium/heavy duty cutting torch.

Herm Williams
06-24-2011, 01:27 AM
We used a dewar for the cutting table for a while but it was not worth the trouble, now we use six bottle in a manifold set up. We use propane on the cutting table (up to six inches thick and five torches) and portabe units. Special tips are a help but you can cut with regular tips, just more difficult to light. I prefer propane for brazeing because I can control the heat better. my two cents worth.
re

Ray C
06-24-2011, 09:19 PM
Sorry, I wasn't clear... Depending on what depot you visit, they'll either test/refill your existing tank or do an exchange. Smaller depots do exchanges.

let's say you wanted 3 tanks refilled (and/or exchanged). They might accommodate 1 or 2 tanks but only if you're a regular, high-volume customer. There are at least 5 large filling centers in this area owned by 3 different companies all within 30 miles of my location. There's another 8 or 10 if you go out another 10-15 miles. My tanks are only registered with one the companies but all of them are telling the same story. Tried to register with the other companies and got turned away -but they did offer to set me up with propylene...

Quick update on this: I called the place I'm registered with and they now provide acy to all customers. Slight price increase by a couple dollars but it's understandable given their distribution/transportation costs probably increased...

gcude
06-24-2011, 09:57 PM
One of my clients got a sales pitch this week to switch to propylene.

Supplier will install lines for entire shop if they will switch and noted that propylene is half the cost of acetylene.

Evan, do you have the ratio for mixture to do a real cost comparison?

Anybody have experience with propylene?

Evan
06-24-2011, 11:51 PM
Acetylene is 1.4 to 1
Methane is 1.9 to 1
Propane is 4.5 to 1
MAPP is 3.5 to 1
Propylene Oxide is 3.6 to 1

Those are the stochiometric ratios tha produce a neutral flame.

That isn't the only consideration though.

Acetylene has the highest flame speed at 22 fps which is almost twice that of propane. That means it stays lit better at high flow rates. Prop is 15 fps and the others are slightly less.

The biggest difference is in the amount of heat in the central flame. Both propane and propylene have much less heat in the central flame and propylene has lower total heat than propane so heating to ignition for cutting takes longer.

The general rule is that the more complex the molecule the less heat in the central flame since it must go through several stages of combustion to release all the heat. By the time all that heat is produced the hot gasses have left the area of interest. Acetylene has many more BTUs in that inner cone which is why it is still the main choice as a fuel gas.

J Tiers
06-25-2011, 12:14 AM
The difference with acetylene is the triple bond between the carbons. That is the reason it is so unstable, AND the reason why it has "central cone heat".

To take a hydrogen off a carbon takes a goodly amount of energy. You get it back, plus more, when oxygen reacts with the two pieces, but you need to "invest" that energy first. That takes heat OUT of the area nearest to the nozzle, since energy from combination with oxygen is partly used to break more carbon-hydrogen bonds in order that the combustion may continue. There is a time delay before you get it back

With acetylene, the triple bond is very unstable, and very little energy is required to break it and make bonding sites available for oxygen. Since the "activation" energy is low, the energy released by combining with oxygen is not "soaked up" by breaking more bonds (to continue the ongoing combustion). So quite a considerable amount more heat is available near the nozzle.

oddball racing
06-25-2011, 08:41 AM
I just got back from swapping my shop tanks and thought I'd share some actual figures.
...Some back ground first.
For about 20 years I used to lease tanks from XYZ gas and then various suppliers due to the fact they were always buying each other out.
I never switched companies; I just allowed them to move my account as they aquired each other. They became A**gas in this area. The cost near the end for a "full-size" shop tank lease was $85 per year for the pair of them.
Three years ago they raised the price enough to force me to buy my own tanks. However , if you "own" your own tanks they cannot be full sized, but the smaller size tank. I also added a mig (mixed) gas as well. Sorry, But I can't recall how much they gouged me to "buy" the tanks. The qoutes on the "buy" word are amusing because even though I "bought" these tanks, they are not mine, they are treated as leased tanks. You just exchange them when they are empty, which is more often so that's how they squeeze more $$$ from us.

The figures are a bit confusing due to the fact of the strange category of tank names.

Acetylene, dissolved Size: 3 (CL UON) 3M300 Was $36.40 with a $5.63 acetylene surcharge.
So, $42.03 for a tank slitghly taller than SCUBA tank.


Oxygen, compressed Size: Indutrial 80 80 cubic feet $20.35 (A tank the dia of SCUBA but waist high.)

"Steel-gas" Argon84/Co16 Size 125 Cu.Ft. $46.20 (Again SCUBA dia but Chest high.)
I feel gouged on the mig gas. Maybe I should switch to straight Co2.
MIKE

bborr01
06-25-2011, 10:19 AM
How about using gasoline instead of acetylene or propane?

There is a manufacturer that makes gasoline torches for cutting and I watched their video on youtube. It was quite impressive and cheap compared to acetylene.
http://www.youtube.com/watch?v=YWAnv3r0CSw

Another thing about cutting torches is that once you get the steel hot enough to melt, the oxygen does the work as Evan stated earlier.

I read in a welding handbook that you can actually turn the acetylene off once you start the cut and the oxygen will continue the cut. My neighbor and I tried it and it works somewhat, although it is not practical to do this.

Brian

Evan
06-25-2011, 12:16 PM
I feel gouged on the mig gas. Maybe I should switch to straight Co2.


Argon is a real money maker. It is a byproduct of distilling liquid oxygen and when the argon storage capacity at a LO2 plant is full it is simply vented off. Argon isn't rare at all, every cubic metre of air contains a litre of argon. It isn't flammable, it isn't toxic and it requires no special handling other than that required by any compressed gas cylinder. It can be transported in bulk and it liquifies easily.

You are being ripped off.

QSIMDO
06-25-2011, 01:15 PM
For about 20 years I used to lease tanks from XYZ gas and then various suppliers due to the fact they were always buying each other out.
ould switch to straight Co2.
MIKE

Were you with Merriam Graves before?

When Airgas bought them out they completely dumped my account.

Mind, they'd have closed their doors on what little I buy but a heads-up would have been nice.