Pressure Vessels:

A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.

Pressure Vessels are Design as per ASME Section VIII Div 1.
Pressure vessels can theoretically be almost any shape, but shapes made of sections of spheres, cylinders, and cones are usually employed. A common design is a cylinder with end caps called heads. Head shapes are frequently either hemispherical or dished (torispherical).

Applications:

• Pressure vessels are diving cylinders, recompression chambers, distillation towers, autoclaves, and many other vessels in mining operations, oil refineries and petrochemical plants, nuclear reactor vessels, submarine and space ship habitats, pneumatic reservoirs, hydraulic reservoirs under pressure, rail vehicle airbrake reservoirs, road vehicle airbrake reservoirs, and storage vessels for liquified gases such as ammonia, chlorine, propane, butane, and LPG.
• Pressure vessels are used in a variety of applications in both industry and the private sector.
• They appear in these sectors as industrial compressed air receivers and domestic hot water storage tanks.