Propane

A compressed gas tank is filled at a higher pressure than what you use.



A propane tank is at a higher pressure, maybe 400psi
The regulator lets out pressure at a useful pressure, maybe 2 to 15 psi

This is what makes it useful as a container - it will last for a while.


If you try to use a propane tank unregulated, you will have a short lasting, flame-thrower
It ain't smart
 
I bought a reg at tractor supply for about 20 bucks and its fully adjustable.Thats hose and connector and all.
 
I'll elaborate a bit;

A propane tank is filled with liquid propane that will stay a liquid in an open container at -45°F. At normal room temperature, it has to be enclosed to prevent it boiling off. The pressure inside the tank is going to be the vapor pressure of propane at the outside temperature. For 70°F that will make the tank pressure be around 100 PSIG. This pressure will only increase if the tank gets warmer, and decrease only if the tank gets cooler or is empty. The internal pressure will not drop any until the tank is empty during use, as long as the tank doesn't freeze up. There-in lies the problem with using a 20 pound tank. As the propane boils off, the endothermic transformation makes the temperature drop. This in turn lowers the vapor pressure. Once it reaches the point where the outside air pressure is the same as the inside vapor pressure, the propane stops boiling and no gas will be delivered.

So the answer is - The pressure will remain the same until the tank is empty or freezes up.

BTW, The above information explains why a propane tank explosion is a very rare event. The tank will have to be exposed to sevre heat before the pressure can reach the bursting strength of the steel tank.
Even in a fire, all the Fire Dept. needs to do is train a hose on the tank to keep the skin temperature low enough to keep the tank pressure below a couple hundred pounds. If the tank valve breaks, and the propane starts burning, then there is almost no change of an explosion, because the tank pressure will remain fairly constant as the propane boils off and creates the flame. If the break is in a larger diameter pipe, and the propane flow is high, the tank will cool itself so low that the flame will barely burn.
 
Regulators are there for a reason, to regulate the flow of propane. Under pressure within the tank it is way too high to be usable. The regulator brings the pressure down to a working level for propane appliances, which is about one pound per square inch.
 
Don't worry everybody I am using a commercial propane torch on zaph1's two brick forge I bought at USAknifemaker. The problem I am having is I can only get a round file to only non magnetic. The tank i am using is less than half full and I was thinking maybe the pressure was dropping off. By the way I am pleased with the quality and design of the forge zaph1 did a good job .I am new to this never seen a forge run in person. So any help would be helpful
 
PM sent.

The MT245C torch works fine until about 1-2 lbs. left in a 20lbs. tank. The orifice in the MT245C torch acts as a partial regulator. The orifice is .005" which lets through about 1/20 the amount of gas as the .023" mig tip normally used on custom burners. If you remove it, you will have a VERY large flamethrower without a separate regulator. It is highly tuned and without it you would have a very unclean burn, with most of the flame occurring outside the chamber.
 
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If the pressure stays constant unless the tank is empty or frozen, is there some particular reason why my ghetto fish cooker forge regulator needs to be tweaked every few minutes to maintain temperature? Do I need a better regulator than the one that came with the fish cooker?
 
The more empty the tank is, the faster it cools itself down. A 3/4 empty tank will cover itself with frost on a 100°F day in July after running for a half hour.
 
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