Material Specification

The maximum temperature, pressure, and other parameters for which equipment is designed and rated. Design conditions define the mechanical design basis and determine the minimum required wall thickness, material selection, and construction code requirements. Actual operating conditions should remain within the design envelope — operation outside design conditions requires engineering assessment and potentially re-rating or modification.

Additional wall thickness added to the minimum required thickness during the design phase to compensate for expected material loss due to corrosion, erosion, and other degradation mechanisms during the equipment's design life. Corrosion allowance is the buffer between the as-built thickness and the retirement thickness — once consumed, the equipment has reached its design end of life.

A specific process or phenomenon that causes degradation of material properties, leading to eventual failure of equipment. Damage mechanisms include corrosion (uniform, localized, galvanic), erosion, fatigue, creep, hydrogen damage, stress corrosion cracking, embrittlement, and other metallurgical or environmental attack modes. API 571 catalogues over 60 damage mechanisms relevant to refining and petrochemical equipment.

A physical item of plant, equipment, or infrastructure that has value to an organization and is subject to management decisions regarding its acquisition, operation, maintenance, modification, and disposal. In asset integrity management, assets include pressure vessels, piping systems, storage tanks, rotating equipment, structural components, electrical equipment, and instrumentation systems. Each asset has an identity, a defined function, and documented attributes.