Failure Cause

The specific manner in which a component, subsystem, or system fails to perform its intended function or performs it in an unintended way. A failure mode describes the observable manifestation of a failure — what goes wrong — rather than why it goes wrong (failure cause) or what happens as a result (failure effect). Each functional failure may have multiple failure modes.

The consequence of a failure mode on the operation, function, or status of the item and the system. Failure effects describe what happens when the failure mode occurs, traced from the local effect on the component through the system level to the end effect on the plant, safety, and environment. Effects must be described assuming no detection or compensating provisions are in place.

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 systematic investigation methodology used to identify the fundamental underlying cause(s) of a failure, incident, or undesired outcome. RCA goes beyond the immediate or proximate cause to uncover the latent organizational, procedural, or design factors that created the conditions for the event. Common RCA techniques include 5-Why analysis, fishbone (Ishikawa) diagrams, fault tree analysis, and barrier analysis.

A systematic, proactive methodology for evaluating a process, product, or design to identify all possible failure modes, determine their effects on system performance, rank them by risk priority, and recommend actions to reduce or eliminate the highest risks. FMEA examines each component's potential failure modes, their causes, effects at local/system/end levels, current controls, and risk priority numbers.