When cutting open a propane tank, safety is the key ensure there are no explosions or accidents. It is important that the proper steps be taken to prepare the tank for cutting before the cutting procedure begins. If these steps are not followed, the person making the cut runs the risk of an explosion.
Remove the valve and turn the tank upside down, allowing all liquid to properly drain from the tank. Allow the tank to sit with the hole open so it can breathe for at least seven days. Remove any remaining fittings using a pipe wrench (if the fittings are old, this may require force). Avoid making sparks during the removal of the fittings and valves. Use a rubber mallet to tap the wrench, if necessary.
Purge the tank again to ensure all propane gas has been removed. To do this, fill the tank with water through the fill valve (the tank should be sitting level while this is being done). The tank should be so full of water it is running over the sides. Repeat this process twice before attempting to cut the tank open.
Put on a pair of leather gloves and No. 5 shaded goggles. Using a quality cutting torch with a clean tip, make a straight, clean cut to the tank. If all the proper steps have been taken, the tank can safely be cut open.