Pressure Vessels are closed lid containers which have been designed to hold liquids or gases at pressures substantially different from the ambient pressure. (The pressure outside of the container)
During the history of their development many fatal accidents have occurred due to the dangerous differential pressure, and consequently their design, operation and manufacture have to be regulated by rules and regulations which are backed up by law.
The definition of a pressure vessel changes from country to country, however it still involves parameters such as the maximum safe operating temperature and maximum pressure.
They are used and seen in many different industries and some of their uses and applications are:
o Diving cylinders
o Nuclear reactor vessel
o Road vehicle airbrake reservoir
o Hydraulic reservoir
o Storage tanks for butane, ammonia, propane and chlorine gases and liquids
They can take practically any shape depending upon its application, however the most commonly used shapes are cones, cylinders and spheres. A very popular design for them is a cylindrical shape with a hemispherical end cap.
In theory a sphere is the best shape for a pressure vessel; however a spherical shape is quite difficult and expensive to manufacture so cylindrical shapes are more commonly employed. Small vessels can be manufactured from a pipe and two end covers.
Most are made of steel, but they can be manufactured from any material which has good tensile properties, and is chemically stable for the desired application. Other materials such as carbon fibre which are held in place with a polymer can also be used due to its high tensile strength, it is much lighter than steel but more difficult to manufacture. Some composite materials may be wrapped around a metal liner forming a composite overwrapped vessel.
They can be lined with other types of various metals, ceramics or polymers to help prevent leaking, and also to help protect the vessels structure from the contained fluid or gases.
Pressure vessels are designed to work safely at specific temperatures and pressures. Any vessel that is not designed by the desired code or codes represents a significant safety hazard.
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