Store pressurized tanks?

[SDAnderson]

Whats the reasoning for storing an alum tank upright? I've always stored tanks laying down and blocked to prevent rolling. Thats for all gas cylinders (scuba and industrial cylinders), unless I have a tank rack available to secure them. I always lay them down so they don't get knocked over and go flying if the head gets knocked off.

Tanks should always be stored standing up because the bottom is thicker to allow for minor corrosion - internally or externally - that might accidentally occur. Laying tanks down keeps them from falling over but upright tanks can be secured with a short loop of chain to the wall.