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.