A gas cylinder is a pressure vessel for storage and containment of gases at above atmospheric pressure. High-pressure gas cylinders are also called bottles. Inside the cylinder the stored contents may be in a state of compressed gas, vapor over liquid, supercritical fluid, or dissolved in a substrate material, depending on the physical characteristics of the contents. A typical gas cylinder design is elongated, standing upright on a flattened bottom end, with the valve and fitting at the top for connecting to the receiving apparatus.
A gas regulator attached to a nitrogen cylinder. From right — cylinder valve, cylinder pressure gauge, pressure control valve (yellow) on regulator (green), outlet pressure gauge, 3-way outlet terminated by needle valves.
It would be safer to have cylinders individually anchored in a cool place, rather than chained in a cluster in the sun, as seen here.
Hydrogen storage cylinders in a cascade filling system
Helium quad for surface-supplied diving gas
Storage tanks are containers that hold liquids or compressed gases. The term can be used for reservoirs, and for manufactured containers. The usage of the word "tank" for reservoirs is uncommon in American English but is moderately common in British English. In other countries, the term tends to refer only to artificial containers. In the U.S., storage tanks operate under no pressure, distinguishing them from pressure vessels.
Cylindrical fuel storage tank with fixed roof and internal floating roof. Capacity approx 2,000,000 litres
Horizontal, cylindrical shell, elliptical heads carbon steel pressure vessel
View of Fawley Refinery large atmospheric tanks
Spherical gas tank farm in the petroleum refinery in Karlsruhe MiRO
