Glossary term
Pressure Vessel
A container designed to hold gases or liquids at pressure substantially different from ambient pressure.
Definition
deviceA container designed to hold gases or liquids at pressure substantially different from ambient pressure.
A pressure vessel is a container designed to safely contain internal or external pressure under defined temperature, loading, material, fabrication, inspection, and code conditions. It includes boilers, receivers, reactors, separators, storage vessels, autoclaves, heat-exchanger shells, and compressed-gas containers.
A pressure vessel stores or processes fluid at a pressure significantly different from ambient. Because stored pressure energy can be hazardous, pressure vessels are normally designed and inspected under recognized codes, with defined allowable stresses, materials, weld procedures, safety relief, testing, and documentation.
For a thin-walled cylindrical vessel under internal pressure, a first-order membrane hoop stress estimate is:
where p is internal pressure, R is vessel radius, and t is wall thickness. Real vessel design includes longitudinal stress, heads, nozzles, supports, local reinforcement, corrosion allowance, external pressure buckling, thermal stress, fatigue, and code-specific joint efficiencies.
Design and operation
Key inputs include design pressure, design temperature, fluid, corrosion environment, cyclic duty, material toughness, fabrication route, weld category, inspection class, relief-device capacity, and test pressure. Vessels may fail by plastic collapse, brittle fracture, fatigue crack growth, corrosion thinning, creep, buckling under external pressure, nozzle overload, or weld defects.
In service, inspection and maintenance are part of the safety case. Non-destructive testing, thickness surveys, hydrostatic testing, pressure relief testing, corrosion monitoring, and repair procedures must be consistent with the vessel’s code basis and degradation mechanisms.
Common mistakes
A common mistake is to size wall thickness from pressure alone while ignoring temperature, corrosion allowance, weld efficiency, nozzles, supports, cyclic loading, and relief requirements. Another is confusing operating pressure with design pressure or using gauge and absolute pressure inconsistently. A robust review states code edition, design conditions, material certification, inspection requirements, relief basis, corrosion allowance, test pressure, and service history.