Methane?

[Hamilton Taylor]

We run all our torches on natural gas in the studio - but only because we can - some torches need to be altered to run on natural gas.
The barracuda will run on propane or natural, with no modification. Minors and midranges are the same. I don't remember any GTT literature saying they will only run on propane, and I've certainly run a bobcat on natural gas without a problem. Propane is hotter, and will keep a bigger gather molten and workable, but there is always more natural gas in the tap. Horses for courses....

Sean

[helenfc]

thanks sean...the only question now is would it work on a hothead? will eventually save up for a minor I hope, but bringing in a propane tank to the workshop is out of the question (unsurprisingly) i just dont want to ruin my wee hothead... also it would only be for a week and back to running on propane after that. maybe i should just forget it for now! 

[Bluebottle]

thanks for that link dawn very helpful
mike what sort of modifications would need to to be made to a hothead?
its interesting to see people work minors off it though.

Hi Helen, the injector orifice ( the part that the gas goes through in the burning head ) would need to be drilled out to allow more
gas through as would possbly the rest of the torch as the valve openings will be very small HTH

Mike   

[helenfc]

aaah isee
thanks mike, much appreciated, guess I will just resort to mapp for a week then 

[Bluebottle]

aaah isee
thanks mike, much appreciated, guess I will just resort to mapp for a week then 

I'm glad someone understands, it took me a while 

Mike   

[helenfc]

yes my techno jargon comprises of 'thingys' and 'stuff'  takes a wee while for the penny to drop sometimes!

[stuwaudby]

Must add the fact that I'm a gas engineer to my profile....

MAPP is a mixture of highly reactive gases, predominantly propene. It is less stable than propane or methane so therefore breaks apart more easily releasing more energy in a smaller volume of flame.

Methane will theoretically burn at similar temperatures in air but the temperature glass can reach in a flame depends on a number of factors:

First the science:

When heating glass there is a balance of heat input and heat loss, sufficient heat must be input to overcome the dilution of the flame by the surrounding air and radiant loss from the glass. The velocity of the burning gas mixture increases the heat input rate. A greater sized flame reduces air dilution.

MAPP has a vapor pressure of 97 PSI @ 70F (the pressure in the can) which is equivalent to 6.7 bar. This means the velocity of the gas is very high in the burner (which is why they are so noisy).

UK domestic gas is typically delivered at 20 mbar  = 0.02 bar

A hot head could be modified to burn domestic methane by modifying the mixture hole sizes, however:

Using Bernoulli's equation for oriface plate flow the mass flow rate is proportional to the root of the pressure. The MAPP will deliver 18 times more heat than domestic methane. Considering that MAPP can hardly manage to melt thick rods, domestic methane would stand no chance.

It is feasible that domestic methane could be pressurized to 7 bar and would work great in a hot head. The cost of the equipment would be far in excess of Oxy propane, probably illegal and not something I would want near my house.

My advice is take the plunge and buy an oxy propane set up. After two bottles of MAPP I switched. You also get that advantage of being able to listen to trance music while creating

[helenfc]

thanks stu, but i already have a bulk propane set-up, my question was actually because its a breach of health and safety regualtions to have a propane tank in the workshop at college, and I wanted to take my hothead in for a week. fortunately i took the plunge straight away when I started and never had to use mapp! turns out I can melt glass with the natural gas at college, but it makes it cloudy and dirty.
welcome to fh by the way!