API RP 571

Covers — descriptions of damage mechanisms affecting fixed equipment and piping in refining/petrochemical service: general and localized corrosion, high-temperature damage (sulfidation, HTHA, creep), environmental cracking (chloride/caustic/amine SCC, HIC/SOHIC), and mechanical/metallurgical mechanisms, each with critical factors, morphology, and mitigation/monitoring.

Does NOT cover (exclusions) — the following are governed elsewhere:

• The in-service inspection program and intervals → API 570 / API 510.
• Detailed inspection practices/techniques → API RP 574.
• Risk-based inspection methodology → API RP 580 / 581; fitness-for-service → API 579-1.

RP 571 tells you what can go wrong and why; the inspection and RBI codes decide what to inspect and how often.

RP 571 provides reference knowledge for each damage mechanism:

• Affected Materials — which alloys/grades are susceptible.
• Critical Factors — temperature, environment, stress, and concentration thresholds that drive the mechanism.
• Appearance/Morphology — how the damage looks and where it initiates.
• Prevention & Monitoring — mitigation measures and the inspection/monitoring methods that detect it.

API RP 571 is the reference encyclopedia of damage mechanisms affecting fixed equipment and piping in refining and petrochemical service. For each mechanism — sulfidation, high-temperature hydrogen attack, corrosion under insulation, chloride and amine stress-corrosion cracking, and dozens more — it describes the susceptible materials, critical factors, appearance, and mitigation/monitoring.

It is the knowledge base that makes risk-based inspection possible: you cannot inspect for a threat you have not identified. RP 571 informs where and how to look, feeding the inspection code (API 570) and RBI methodology (API 580/581), but it is not itself an inspection or acceptance code.

Engineering Note: Use RP 571 to build the equipment's credible-damage list before setting inspection plans — an unrecognized mechanism (e.g., HTHA in a hot hydrogen line) is a classic cause of in-service failures that a generic thickness-monitoring plan will miss.