MAPP gas versus Acetylene

I have asked this question and seen others ask, but have yet to read an a answer that seems satisfactory.

If MAPP gas and acetylene have almost the same flame temp, MAPP has more heat in it, MAPP gas is cheaper and safer to handle, and MAPP gas is known as being as good or better than acetylene at heating, cutting and brazing, then WHY, other than availability of the tanks and gas, would MAPP gas NOT be used for welding? And be highly preferable to acetylene?

I did see someone comment that copper and MAPP gas could be explosive. Is that true?

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Jack Bauer wrote:

It's not anything to do with copper and MAPP. It's chemistry. There is a lot more hydrogen available in the MAPP flame then in the acetylene flame, so welds done with MAPP (or any other LP derivative) suffer from hydrogen embrittlement.

Here is the section on fuel gases out of the notes from Ernie's gas welding class:

Fuel gases:

Acetylene: made from dripping water on calcium carbide, acetylene used to be user- generated for everything from toy "carbide cannons" to household gas installations which had an acetylene generator in an outbuilding, generally a blockhouse about 100 feet from the main home with 3 walls made of concrete blocks and the 4th wall (the one that faced away from the house) made of wood so that if the acetylene exploded, the wood wall would fail and the blast energy would be directed away from the home. Acetylene generators were also used in industry and are still around as quaint period pieces, but insurance practices now dictate that acetylene production all be done in large plants. The welding gas industry would love to see acetylene go away entirely because of the astronomical insurance costs associated with handling it, but it is necessary for welding as no other gas has its attributes of heat without excessive amounts of elemental hydrogen being introduced into the weld metal.

very expensive fuel only fuel gas appropriate for welding steel

Propane/Chemtane/MAPP/Propylene/Flameall: (LP gasses) not suitable for welding, best choice for heating or cutting use same regulator as acetylene propane is a much cheaper gas than acetylene

Grant Erwin Kirkland, Washington Seattle Metalheads welding class facilitator (Ernie Leimkuhler, teacher)

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"

One of my memories from about 1940 is of my uncle and cousins removing the acetylene generator from the basement of a Kansas farm house. There was no particular blast or fire protection evident. There was no electricity yet and the gas had not been used for many years but there were still outlets for acetylene lights in each room. I remember they dumped the generator and it was full of the same carbide residue I remember my dad removing from a welding acetylene generator some years later.

Don Young

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Besides Grant's quote from my seminar you will soon find MAPP non-existent. This has to do with one of it's constituent gasses. MAPP is Methyl-Acetylene Poly-Propylene. One of the gasses used to make MAPP is Propadiene. Propadiene is now worth more to the plastics industry than it is to the welding industry, so MAPP is being phased out. In Seattle it is almost impossible to get in anything bigger than a disposable propane torch sized can.

The replacements for MAPP are numerous. I have used Flamal, Propylene, and Chemtane, and all work fine for cutting, heating, and brazing. They are all hotter than basic Propane.

Honestly I gave away my large acetylene tank in my shop 3 years ago, and have never missed it.

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"Ernie Leimkuhler" wrote: (clip) The replacements for MAPP are numerous. I have used Flamal, Propylene, and Chemtane, and all work fine for cutting, heating, and brazing. They are all hotter than basic Propane.

^^^^^^^^^^^^^^ I'm trying to figure out what this all means. I notice you did not list welding among the uses for Mapp gas equivalents. Yet you gave away your large acetylene tank. Do you do all your A/C welding with a smaller tank? Since I use acetylene for light welding jobs as well as heating and brazing, and I use medium and small tanks, should I just continue what I am doing? Can you weld with these other gases? Will they work in the same torches that are made for acetylene?

Thanx for any info and clarification.

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Leo Lichtman wrote:

You must have missed my post. The only fuel gas that doesn't inject too much hydrogen into a weld is acetylene.

Ernie doesn't do torch welding, he does TIG welding.

Grant

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"Grant Erwin" wrote: You must have missed my post. The only fuel gas that doesn't inject too much

^^^^^^^^^^^^^^^^^ Thanks, Grant. I do remember reading your post, but it didn't sink in. It's all clear now.

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Leo Lichtman wrote:

And yes indeed, you can use acetylene regulators for any propane gas or derivative (MAPP, Chemtane, etc., see Ernie's post for a list). At least they'll bolt up fine. I use mine for any fuel gas if I need to.

Grant

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I last gas welded in my shop around 10 years ago. It has absolutely no commercial value to me as a fabricator.

Mind you, at school I spent 9 years gas welding almost every night. That is because it is still the best way to TEACH welding.

I have even gas welded at the Divers Institute as a demo for the students.

Everything I do is either MIG, TIG or Stick welded.

I do still have a tiny MC cylinder of Acetylene for jewelry work.

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"Ernie Leimkuhler" wrote: (clip) I do still have a tiny MC cylinder of Acetylene for jewelry work. ^^^^^^^^^^^^^^^

Wouldn't MAPP gas and equivalents be suitable for that also?

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No, because acetylene is still the hottest gas and is able to be focused to a much tinier point than any LP gas.

So for jewelry work using a micro torch, you can work faster and cleaner.

A lot of jewelers and plumbers use acetylene/air torches, often called Prestolite torches. They give a soft heat that is very controllable, and with the size of the work being done, a MC tank lasts a while.

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Leo Lichtman wrote:

Since the majority of jewelry work is hard soldered (brazed), many jewelers use a big bushy flame that heats the whole piece. I have an oxy-acetylene Little Torch, but only use it for fusion and casting. For most work I use propane or air-acetylene.

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mbstevens
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"mbstevens" wrote: Since the majority of jewelry work is hard soldered (brazed), many jewelers use a big bushy flame that heats the whole piece. (clip) ^^^^^^^^^^^^^^^ This makes sense for a piece of jewelry that doesn't have other hard soldered joints that must not remelt. Ernie's use of a small oxy/acet torch would be best for restricting the spread of heat from other joints.

A second thought: You can always spread the heat by moving a sharp flame, but you can't focus the heat from a bushy flame.

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Leo Lichtman wrote:

Actually, the usual practice is to use 'hard', 'medium', and 'easy' hard solder. These are more like brazing fillers (not soft solders) that have slightly different melting points. You start with the highest melting 'hard' solder, then work through lower melting points on successive attachments. It is very unusual to have a piece that needs more than these three melting point fillers. The three are available in both gold and silver from jewelry supply houses.

It is certainly possible to use a small hard flame to hard-solder gold successfully, but with small pieces of silver you can easily cause the base metal to collapse before the solder has even had a chance to finish flowing. The other problem with small oxy-acetylene flames for hard-soldering gold and silver is that it gets quite hard to see what is going on.

The hard flame does make sense for repairs when you don't know the melting points of the joins on the already soldered piece.

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