MyloFiore wrote:. I just think that just because you have done something risky for 10 years does not mean that you are any less likely to fall prey to some circumstance that could have easily been avoided with a much safer alternative.
[stepping off the soapbox]
Can I have your gear if you "eat the dirt sandwich"?
Mylo
I understand your concern but consider the following.
Pressure in a propane cylinder is dependent on the temperature as any gas contained in a tank:
At a temperature of 70° F, propane's vapor pressure is 124 PSI.
At a temperature of 100° F, propane's vapor pressure is 172 PSI.
At a temperature of 162° F, propane's vapor pressure is 390 PSI.
Propane tanks are equipped with pressure relief valves that vent excess pressure.
Normal propane cylinders, such as those used with portable grills have pressure relief valves set to 375 PSI. PRV settings for ASME (American Society of Mechanical Engineers) tanks are 250 PSI. DOT engine fuel cylinders use PRV settings of 312.5 PSI.
During manufacture of propane cylinders each propane cylinder must be exposed to two times its service pressure, and one out of every 500 cylinders is exposed to four times its pressure, or about 960 PSI.
Chilling the bottle lowers the pressure dramatically and will also lower the flow rate of the Propane. I was dealing with temps down in the low 20's and bottle temps even lower due to the cooling effects the gas has as it expands and leaves the tank. My tank pressures were probably well under 100psi and falling. There was actually a good bit of ice forming on the outside of the tank. Most propane burner are designed to work with tank pressures of around 125 psi, which is the approximate pressure of a normal bottle at room temperature. I could lay my hand on the bottle immediately after removing the flame and it was no where near 70 degrees, probably more like 45 or 50 degrees. It was still cool to the touch.
Think about how long it takes to bring a volume of liquid to boil in your kettle. It would take an extended exposure to the flame to raise the temp in the tank even 50 degrees.
Also take into account that you have to have a little common sense about what you are dealing with. If you have and exchange/rental propane tank with an unknown history... well just don't have one of those. My tank is less than a year old and is a good quality tank stored indoors. I have it filled locally and not exchanged. I know my tank has not been dropped or damaged as I stand and chat with the guy as it is being filled.
The first time I saw someone hit a Nitrous tank with a torch I thought they were nuts too. Then the engineer in me put some thought and reading into it. By the way the pressures in Nitrous Oxide tanks are in the 600 to 1000mpsi range. Oh by the way yes there is a fair bit of the ol' engineer in me but there is also a ton of redneck in there as well and yes I have thrown a propane tank in a bonfire to see how long it would take to explode. It was much longer than you would have thought. I have also shot one with a .50 caliber rifle from about 380 or 400 yards. Yes it was fun.
Bottom line and disclaimer for all the stupid people out there. If you do not know the intimate details of what you are doing do not play around with gases, flammable liquids, and open flames. in other words do not try this at home.
