Pressure vessels are an inseparable
part of the process industry. Many
critical reactions need to be carried
out in closed vessels at elevated
pressures and temperatures. Some reactions
can be explosive in nature. Pressure
vessels are carefully designed and
manufactured equipment to handle such
extreme conditions of temperature
may 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
hemispherical or torispherical end
caps called heads.