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Pressure Vessel:

1) A Metal container generally cylindrical or spherical, capable of withstanding

various loadings, is called pressure vessel.

2) A pressure vessel is a container designed to hold liquids or gases and store them

under high pressure.

3) A cylindrical or spherical metal container capable of withstanding pressuresexerted by the material enclosed.

4) A pressure vessel is a closed, rigid container designed to hold gases or liquids ata pressure different from the ambient pressure. The end caps fitted to the cylindricalbody are called heads.

Pressure vessels are important because many liquids and gases must be storedunder high pressure. Special emphasis is placed upon the strength of the vessel toprevent explosions as a result of rupture. Codes for the safety of such vessels havebeen developed that specify the design of the container for specified conditions.

Most pressure vessels are required to carry only low pressures and thus areconstructed of tubes and sheets rolled to form cylinders. Some pressure vesselsmust carry high pressures, however, and the thickness of the vessel walls mustincrease in order to provide adequate strength.

In addition to industrial compressed air receivers and domestic hot water storagetanks, other examples of pressure vessels are: diving cylinder, recompressionchamber, distillation towers, autoclaves and many other vessels in mining or oilrefineries and petrochemical plants, nuclear reactor vessel, habitat of a space ship,habitat of a submarine, pneumatic reservoir, hydraulic reservoir under pressure, railvehicle airbrake reservoir, road vehicle airbrake reservoir and storage vessels forliquefied gases such as ammonia, chlorine, propane, butane and LPG.

In the industrial sector, pressure vessels are designed to operate safely at a specificpressure and temperature technically referred to as the "Design Pressure" and"Design Temperature". A vessel that is inadequately designed to handle a high

pressure constitutes a very significant safety hazard. Because of that, the design andcertification of pressure vessels is governed by design codes such as the ASMEBoiler and Pressure Vessel Code in North America, the Pressure EquipmentDirective of the EU (PED), Japanese Industrial Standard (JIS), CSA B51 in Canada,AS1210 in Australia and other international standards like Lloyd's, GermanischerLloyd, Det Norske Veritas, Stoomwezen etc.

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Shape of a pressure vessel

Theoretically a sphere or cylinder would be the optimal shape of a pressure vessel.Most pressure vessels are made of steel. To manufacture a spherical pressurevessel, forged parts would have to be welded together. Some mechanical properties

of steel are increased by forging, but welding can sometimes reduce these desirableproperties. In case of welding, in order to make the pressure vessel meetinternational safety standards, carefully selected steel with a high impact resistanceshould be used. Most pressure vessels are arranged from a pipe and two covers.Disadvantage of these vessels is the fact that larger diameters make them relativelymore expensive, so that for example the most economic shape of 1000 liters, 250bar (25,000 kPa) pressure vessel might be a diameter of 450 mm and a length of6500 mm.