Mechanical design develops the physical configuration, dimensions, materials, and specifications for fabricated equipment and components, ensuring designs meet functional requirements while being manufacturable, operable, and maintainable. This engineering discipline combines theory, codes, and practical knowledge.

Design process includes defining requirements and constraints, conducting stress analysis per applicable codes, selecting materials for service conditions, configuring components for optimal performance, specifying fabrication details including welds and tolerances, and preparing fabrication drawings and documentation.

For pressure vessels and process equipment, mechanical design encompasses shell and head thickness calculations, nozzle sizing and reinforcement, support design for various load cases, thermal expansion accommodation, flange and bolting selection, and specification of welding, examination, and testing requirements.

Good mechanical design balances multiple objectives: meeting performance requirements, ensuring code compliance, enabling cost-effective fabrication, facilitating installation and maintenance, and optimizing lifecycle cost. Trade-offs between objectives require engineering judgment informed by experience.