Vessels, tanks, and pipelines that carry, store, or
receive fluids are called pressure vessels. A pressure vessel is defined as a
container with a pressure differential between inside and outside. The inside
pressure is usually higher than the outside, except for some isolated
situations. The fluid inside the vessel may undergo a change in state as in the
case of steam boilers, or may combine with other reagents as in the case of a
chemical reactor.
Pressure vessels often have a combination of high
pressures together with high temperatures, and in some cases flammable fluids or
highly radioactive materials. Because of such hazards it is imperative that the
design be such that no leakage can occur. In addition these vessels have to be designed
carefully to cope with the operating temperature and pressure. It should be
borne in mind that the rupture of a pressure vessel has a potential to cause
extensive physical injury and property damage. Plant safety and integrity are
of fundamental concern in pressure vessel design and these of course depend on
the adequacy of design codes.
When discussing pressure vessels we must also consider
tanks. Pressure vessels and tanks are significantly different in both design
and construction: tanks, unlike pressure vessels, are limited to atmospheric
pressure; and pressure vessels often have internals while most tanks do not
(and those that do are limited to heating coils or mixers).
Pressure vessels are used in a number of
industries; for example, the power generation industry for fossil and nuclear
power, the petrochemical industry for storing and processing crude petroleum
oil in tank farms as well as storing gasoline in service stations, and the
chemical industry (in chemical reactors) to name but a few. Their use has
expanded throughout the world. Pressure vessels and tanks are, in fact,
essential to the chemical, petroleum, petrochemical and manufacturing plants. It
is in this class of equipment that the reactions, separations, and storage of
raw materials occur. Generally speaking, pressurized equipment is required for
a wide range of industrial plant for storage and manufacturing purposes.
Design Procedure
Pressure vessel design philosophy
1. Structural and material consideration
2. Factor of safety
3. Design by rule
4. Design by analysis
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