How much pressure does propane generate you say? It depends on the temperature:
At a temperature of 70° F, propane's vapor pressure is 124 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. If the tank gets too hot, the tank will fart instead of explode
Normal propane cylinders, such as those used with portable grills have pressure relief valves set to 375 PSI. PRV settings for ASME tanks are 250 PSI. DOT engine fuel cylinders use PRV settings of 312.5. IT seems propane tanks are built to withstand at least 250 PSI. its logical to assume that any propane cylinder you are likely to encounter can withstand at least 200 PSI virtually indefinitely.
You have to empty your tank so what i do is hook up a stove or torch fitting light it up and burn of the extra. There will still still be propane in the tank when you remove the Pressure relief valve but it won't be pressurized. To remove the Pressure Relief valve use the tool used to remove valve from bike tires. KEEP THE PRESSURE RELIEF VALVE YOU WILL REPLACE IT WHEN YOU ARE DONE. THe large valve in the middle is check you can just chuck itl.
the hole on the right is the valve you will be replacing. remove the large one in the middle in the same wayThe next step is to wash the smelly gunk out of the tank. allow the inside to dry. now drill the hole in the middle to the size you require then tap for threads. next clean the cutting oil out and pour some paint in, make sure you dont get any on you new threads. swish the paint around coating the inside to prevent rust from the damp compressed air.
replace your pressure relief valve and your done now you have found use for that other wise useless tank.
