Butane vs Propane

[Seriesone]

Good evening everyone, I am from Malta and I am new to this forum. Apologies if the question I am going to ask has already been asked but I could not find it.
I attended an evening class course on welding and one of the items covered was that propane gives a significantly higher temperature flame than butane. When I tried to look up some technical data on the web I found that the only difference between the two gases is that propane freezes at a lower temperature than butane, that is why it is the preferred gas to use in workshops.
What is the difference in practice between the two gases and can they be used interchangeably especially with oxygen?

 

[Hitch]

You are right, they do both burn at about the same temperature, when mixed with air.
Oxy/Propane burns around 2800 oC. Butane and oxygen, never heard of the two being paired up in a normal enviroment, i recall someone mentioning that it requires far more oxygen to reach temperature than Propane...
Stick with the propane, or acetylene.

 

[^neo^]

Doesn't butane (in the calor bottles) run at a lower pressure than propane?
Seem to remember an old caravan we had you have to change the pressure on the water heater for either propane or butane.

 

[aametalmaster]

I think Butane is higher pressure than Propane thats why its kept in round Vessels. I work in the (Deprop) propane c3/ (Debute) butane c4 unit in a refinery but i never tried it in a torch...Bob
http://en.wikipedia.org/wiki/Propane
http://en.wikipedia.org/wiki/Butane

 

[Omniata]

Propane should be higher pressure on account of it's lower boiling point.
Propane is a 3 carbon unit boiling at about -42°C
Butane is a 4 carbon unit boiling at about -0.5°C

General formulae for combustion are:

Propane: C3H8 + 5O2 > 3CO2 + 4H2O

Butane: C4H10 + 6.5O2 > 4CO2 + 5H2O


Butane requires more oxygen but as it has a lower pressure and lower thermodynamics than propane, as it requires more energy to break it up....

In the light blue inner cone of the flame, propane can engage in propadiene and acetylide radical formation, these release large amounts of energy at the edge of the inner cone...

Butane can't do this as easily as so much energy is required to break the molecule down into "bite sized" pieces...


Hope this helps

 

[weldingscotty803]

nice one jim

 

[pedrobedro]

Can you use propane instead of acetylene ? The only time we tried it the weld came out like coke and just dissolved when you flexed it.

 

[zardoz]

No you cant weld with propane and oxygen, only braze, or cut.

 

[Omniata]

It's not hot enough to weld...

It will only cut as it heats the metal near to the melting point and the jet of oxygen oxidises it and blasts it away...


MAPP gas is used across Europe as it can be liquified, it's a mixture of methyl-acetylene and propadiene with a trace of LPG...
It gets very close to the flame temperatures of acetylene but unfortunately the secondary cone is much hotter than with acetylene. This means the area around that which your welding tends to melt first

Another alternative available here in the UK is Propylene, gets a bit hotter than Propane with O2, it tends to be used in special applications though...