Under pressure

Last year sometime I got, free of charge of course, a gas tank, and a car's air-conditioning compressor. I wanted, you see, to build an air compressor. But I procrastinated with it, as per usual, for two reasons: the tank still had propane in it, and I had no safety valves. Well, today I found someone who will sell me the appropriate valves and regulators etc, so I will get cracking as soon as possible. I mean to buy parts on Saturday. Here is my plan of attack:
Note: It's only a schematic, it won't look like that when I'm done.