You are talking about the 1# cylinders. They are fine in any position. I use a lot of them in product demos and have never had a problem in any way.

Acetylene bottles are the only ones that should be stored upright. That means on a service truck or in a shop where where the bottle is used on short notice. They may be stored lieing on side long term if they are set upright at least 1 hour before use. Opinions differ on useing other bottles while on their side,I normally use them all upright .

It does not matter if they are up right or on their side.

The important thing is to keep the threaded part of the tank clean. Covered so that debris cant not get down into the needle valve.

Thank you all for the info.

The safest position for storing and transporting ANY pressurized vessel is UPRIGHT. This has nothing to do with using the bottle, rather it is to maintain the safest trajectory should the top of the bottle become damaged or fail causing rapid pressure release, effectively turning the bottle into a missile.

Since I have no way or storing or transporting it upright in a sturdy closer container, isn't it preferable to be on its side in a latched metal tool box? It is more protected that way from damage. I just was worried that there was some problem with the liquid propane being in constant contact with the valve when laid on its side.

Perhaps you should have asked: "Here is how I intend to do it, so can you please validate my decision?"

In that case: Sure. Go for it.