Using butane in an oxy-propane torch?

[birdingbenny]

Hi,
I'm looking at buying an oxy-propane torch for general heating and brazing. I have a nearly full tank of butane and was wondering if it is possible to run that through the torch, to save the expense of yet another canister!
Cheers, Ben

 

[Jim_gsxr1000]

No, you cant maintain the pressure and flow rate i supose you could if you wer somewhere warm like the middle east but u would draw butane off and because the boiling point of butane is much closer to 273K when you start to draw of gas at the the required flow rate the bottle would cool down and stop you getting the required pressure where as propane boils at 231K so you can maintain pressure and flow rate

 

[bambuko]

...propane...you can maintain pressure and flow ...

Even with propane, I find that I need to tweak the regulator to keep the flow and pressure as desired.
Don't know whether it is because I am using single stage regulator? (would two stage be better?) or is simply because propane bottle I am using is rather small?

 

[Jim_gsxr1000]

wouldent be much in it, 2 stage is for MP and HP gas cylnders more so, with a single stage you flow rate will increase as your pressure drops in the bottle, but propane is a gas take off with liquid bottom, wouldent make much differance

 

[bambuko]

OK, so why is it, that:
I set up the regulator at the beginning of brazing with propane at around 5psi, everything is fine and after some time I notice that both flow and pressure of propane drops and I need to adjust the regulator?
Once adjusted second time it's usually fine and OK for the rest of the brazing session.
If it's not the regulator, than is it the bottle? or am I doing something wrong?

ps I guess HP=high pressure, but what's MP=?

 

[Jim_gsxr1000]

I was explaining the use of 2 stage regs, they are mainly for HP (high pressure 230BAR and over) and MP(medium Pressure 137 BAR) mostly found on oxygen cylnder or argon cylnder (compressed gas) not liquified as is the case with LPG (propane) there isnt realy a need to use a 2 stage with propane as the gas take of rate is totaly dependant on 3 things.
1: the surface area of the liquid in the bottle
2: the ambiant temperature
3: the diamiter of the orifice in this case the valve which is a constant

as the gas is used the temperature in the bottle drops and as pressure and temperature are directly proportional your pressure will drop aswell, so after a short time providing you arent drawing a massive quantity of gas off you will find that once you re adust its close the point where the gas is boiling off as fast as your using it.

 

[bambuko]

Thanks, and understand the regulator bit.
As for the need to re-adjust propane pressure after working for a bit - it sounds like it is perfectly normal and nothing to do with the size of the bottle?
My thinking was that if I were to get a bigger bottle it would be less affected by temp (and consequent pressure) drop?

 

[Jim_gsxr1000]

Yeh its a normal thing to do, i only use propane for cutting, but a bigger bottle at indoors temp will require less adusting

 

[dannyp]

butane has higher boiling point so you find the cylinder tempriture will fall down to it much quicker then your gas pressure in the cylinder will fall off quick

 

[birdingbenny]

Very interesting replies, thank you. So propane for brazing then.

Does this mean that butane is no use in less than warm ambient temperatures then, i.e. never in the UK?! What is it used for then? The only thing I can think of is indoor heating?

BW Ben

 

[Lawnmowerboy]

Caravans. Camping and camping cookers

 

[Jim_gsxr1000]

u can use it in the summer in the uk, but propane is better, seen butane used in Egypt

 

[dannyp]

it's got a boiling point of -1 deg C

usefull for indoor heaters , BBQ's and things like autogas where its fed into a heated vaporiser as a liquid. i used butane kit for camping once and regreted it.

propane boils at - 42 deg C much more usefull

 

[KemppiFrog]

For the last 40 yrs I have used butane for cooking. When it is cold, there is a tendancy for the flow rate to fall, esp if below freezing. But so far this year, I have not had to warm the bottle. Lowest temp was -5C. Of course the flow rate is lower. If for a gas torch, then it would be a problem.