Pressure vessels are all around us. Most of us don’t realize how often we rely upon them and in how many places and situations they are used– from a spaceship way up in the sky to a submarine at the bottom of the ocean to the familiar red fire extinguishers in our kitchens, the list of types, shapes, sizes and purposes just doesn’t quit and I would bet one would have a very difficult time not depending on one kind or another in a day’s time.
A pressure vessel is, as its name indicates, a container which holds its contents— whether it be a liquid or gas— at a specific pressure. Most have cylindrical shapes and many hold harmful gasses, such as oxygen and nitrogen. Because gas and liquids are able to be maintained at pressures different from those of the atmosphere, pressure vessels are valuable for many different contexts and environments. They are typically made out of steel— specifically stainless steel— because of its tensile strength and resistance to corrosion and outside forces. In addition to steel, the container is also often lined with other metals, ceramics or polymers, providing it with extra protection against cracks and leaks.
In addition to stainless steel, many pressure vessels are made of other composite materials, such as filament wound composite and carbon fibre via a polymer; these kinds of vessels can be very light but are very hard to make. This can, if needed, be included with steel as a top layer, providing extra strength and protection from leaking and contamination. Other common materials used in pressure vessels include polymers such as PET, such as in soda cans and copper in plumbing.
A spherical vessel is the most stable shaped container to keep pressurized gas and liquids in, because contained pressure naturally resists against the walls of what is containing, thus a sphere can use this advantageously. Technically, a spherically-shaped vessel has about twice as much strength as a cylindrically-shaped vessel. On the other hand, a sphere is difficult to manufacture and therefore more expensive, which is why you usually find cylindrically or coned-shaped pressure vessels with rounded caps on either end. Despite this commonality, pressure vessels come in a variety of kinds, such as the varying types referred to as “thin-walled”, which are those with a diameter that is at least 10 times greater than the thickness of its walls.
Additional examples include: industrial compressed air receivers, domestic hot water storage tanks, diving cylinders, recompression chambers, distillation towers, autoclaves, nuclear reactor vessels, space ships, submarines, as well as the varying vessels used in mining and oil refineries, petrochemical plants, pneumatic reservoirs, hydraulic reservoirs under pressure, rail vehicle airbreak reservoirs, road vehicle airbrake reservoirs and storage vessels for gasses such as ammonia, chlorine, propane, butane and LPG.