Thanks for all the comments.
Valve to tank threads are just standard (right handed threads). Lefty-loosy to remove.
But there is usually a thread lock (and sealing) compound on the threads.
Use up any remaining propane in the tanks, in something like a gas grill.
Even with all the gaseous propane removed though, there is usually an odorant residue in the tank (to varying degrees).
Since the odorant chemical is a sulfur-containing thiol molecule (vaguely similar to skunk stink

), rinsing with a small amount of soap/detergent and plain household hydrogen peroxide will usually neutralize the odorant.
Or you can use household bleach.
Either use may cause the bare steel inside the tank to corrode.
Before doing ANY cutting, grinding, or welding on a propane tank, remember that not only is the propane flammable but also the mercaptan odorant as well.
Just what are you trying to do with these repurposed propane tanks?
Thanks. I forget how I got the last set of valves out. I think I put the valves into my 6" vise and used a bar to twist the tank off the brass valve. I just remember them being a royal pita to unscrew but it's been a few years so don't remember all the nuances from last time I messed with these things. Last time I only used 3-4 tanks for BBQ smoker fireboxes. Because it was so few tanks I put a handfull or two of pea gravel down the top hole then filled about 1/4 of the tank with dish soap & water then shook it around a bunch manually. Since this is 163 tanks I'll have to figure something else out. Maybe I'll pull all the valves, buy a few plugs/caps and pay the neighbor's kid to run around filling up with a little gravel, few drops of soap, garden hose, plug the tanks then roll them around on my back lawn. I'll post what I'm doing with them at bottom of this comment.
I'm curious what you are building with them? I make fire pits from the 500 gallon end bells, I've processed and cut a few tanks.
That is potentially a decent amount of free propane? Got any blacksmith farrier buddies? Maybe let them burn off what gas is left and get some use out of it. I guess you could weigh and see which ones had the most gas and not just a little vapor pressure. Would be a hassle though.
For that small of a tank volume I'd do the water purge method and invert with the valve opened. Leave them in the sun a few days and most of the stink will bake out. Your neighbors will love you!!
You will need to make a fixture to hold the tank tightly while you mechanically remove the valve. This may require a LONG cheater bar on the older tanks so factor that into the design. If you plan to CUT the valves out then I suggest you invest in some CO2 and just purge, torch and knock them out over a weekend or 2.
I didn't realize how much propane was going to be in the tanks. Actually a lot of them are full or more than 1/2 way full. I assumed they would be empty but didn't realize that they accepted "old tanks" free. There's a LOT of propane. I'd say out of 163 tanks probably 80-90 of them are more than 1/3 of the way full. It was an all-or-nothing deal (I had to take them all) so it's a mix of 20#, 30# and 40# cylinders. (maybe some 15# in there too) Rounding down, 80 15-gal tanks that are 1/3 full is 400# of propane.
How do you recover all that? 50,000 old partially full tanks doesn't do much but maybe I'd buy a 100# tank if there was a halfway decent (and safe) way to consolidate and recover the propane.
Not going to cut the valves out. Will use cheater bar on every single one of them... Won't be fun.
I made a tire bead seater from one of them.
Theirs a flat head bleeder screw on the lower part of the valve opening will vent the tank so be well ventilated area and no flames of course...
Give it and hour or two and you can remove the valve with a decent size pipe wrench it’s best to hold the tank down with a strap to something sturdy it will want to rotate...
Once out I purged with garden hose on trickle for about and hour overflowing and then dumped and let air dry in the sun for a day or 2. And I was good to go
I welded on a 2” black iron ****** to affix valve and nozzle. Which is about to get a serious upgrade cause I happen upon a brand new 2” Industrial ball valve. Vs HDs brass style.
The project worked perfectly I have pictures somewhere. There very strong containers it make sense from public safety standpoint they make them bit tough...
Have any pictures of the tire bead seat machine? That's a cool idea. I have several cars in various forms of disrepair or needing restoration. That would come in handy. You must be a good welder, I don't know that I'd ever trust myself to weld a pressure vessel.
So what am I doing with the tanks: I really have no idea. I'm a lot in over my head. I drive a desk/keyboard for a living. I **** around in the garage as a hobby and stress relief after staring at pixels all day. It was never my intention to go into business making restaurant equipment.
Three things:
~30x restaurant tables with a grill in the center.
~15x urinals from the bigger tanks
And he wants lighting over the bars at two locations (I think I may look for a more appropriate lighting solution)
He's got two brewery/restaurant locations that have outdoor patios, one is a river/boardwalk type thing and the other is on a dock/pier, both fresh water rivers/lakes. He wants 15 six-seat round tables at each location for the outside patios. He wants small gas fired grills in the center of each table that can do both toasted marshmallows/smores and he wants the ability to grill stuff (he does game nights where they have sausage made from different wild game, etc.).
For the table grills I think I'm going to need to do something double-walled and insulated just to keep the bottom cool but still feel open-ish.
The urinals are going to be easy, I'll use the Internet pictures he sent me as inspiration and figure it out.
I think for the lighting that the metal is too thick/heavy gauge. I think refrigerant tanks would be better or perhaps something different.
I'm excited to make 30x of something that involves welding. I've never done this before. Make one, make sure he likes it then just a simple cut list, jigs, LOTS of organization, probably plenty of screw-ups along the way, etc. It's going to be fun.
He wants clear epoxy table tops over wood. Something that the wait staff can easily wipe down and we can glue labels from all the beers the brewery has made over the years. While I think that's a cool idea, I also think that nothing good will happen when combining alcohol with fire and potential flaming marshmallows. Either way, even if it's a disaster it'll be the first time I get to combine multiple things like metal fab/welding and woodworking to build the table tops as well as the composites and epoxy.