The head of a propane tank is a small menagerie of Rounds. This steel cylinder on a forklift truck at the North Carolina Transportation Museum in Spencer, NC, is the way that liquified petroleum gas is stored and transported in small quantities for general use in engines, portable stoves, and residential central heating. As soon as the metered nozzle is opened, the liquid vaporizes. Interestingly, in the production of propane, large volumes are stored in huge, hollowed-out salt caverns around the U.S. Since the gas is denser than air but lighter than other liguids, it is injected and removed from the sealed, pressurized caverns using a salty brine to move it through pipes.

02.20.17