API RP 571, Damage Mechanisms Affecting Fixed Equipment in the Refining Industry, is a recommended practice that describes how in-service equipment deteriorates: the mechanism, affected materials, critical factors, affected units and equipment, appearance or morphology, prevention and mitigation, and inspection and monitoring options. The current edition is the 3rd edition (March 2020). This guide explains what API 571 is and is not, and how inspection programmes use it.
\n\nAPI 571 is a reference catalogue of damage mechanisms. It does not set NDE acceptance criteria, inspection intervals, personnel certification levels, recertification rules or record-retention periods. Those come from other documents: in-service inspection codes (API 510 for pressure vessels, API 570 for piping, API 653 for tanks), construction codes (ASME Section VIII, ASME B31.3, API 650), the employer's written practice for NDE personnel (for example ASNT SNT-TC-1A), and the owner's inspection programme.
\nAPI 571 was written for refining and petrochemical fixed equipment — pressure vessels, piping, tanks, heat exchangers and fired heaters — and is widely used in related industries such as gas processing and chemicals. It is not an aerospace or manufacturing quality standard.
\n\nIntegrity teams use API 571 to identify which mechanisms are credible for each circuit or equipment item, based on materials, process conditions and history. The result feeds inspection plans under API 510, 570 and 653, and, where owners use risk-based inspection, the damage factors in API RP 580/581.
\nFor each mechanism API 571 lists inspection and monitoring approaches. Examples:
\nAcceptance of what inspection finds is governed by the in-service code (API 510, 570, 653) and the construction code. Damage outside those rules may be referred for an engineering fitness-for-service assessment per API 579-1/ASME FFS-1. Atlantis NDT does not perform FFS or RBI assessments.
\nAPI 571 does not define inspector levels. NDE personnel are qualified under the employer's written practice (commonly ASNT SNT-TC-1A, ANSI/ASNT CP-189 or ISO 9712). API also offers an individual API 571 Corrosion and Materials certification for professionals; holders of current API 510, 570 or 653 certification automatically qualify to sit it.
\n\nAPI's exam effectivity sheets cite RP 571 paragraphs such as 3.11 brittle fracture, 3.17 chloride SCC, 3.22 corrosion under insulation, 3.36 high-temperature hydrogen attack, 3.46 naphthenic acid corrosion, 3.61 sulfidation and 3.67 wet H2S damage. Section numbers changed from earlier editions, so always cite the edition you use.
\n\nRefining and petrochemical: crude, coker, FCC, hydroprocessing, amine and sour water units, where sulfidation, naphthenic acid corrosion, wet H2S damage, HTHA, amine and caustic cracking and CUI are typical concerns.
\nGas processing and chemicals: similar mechanisms apply where materials and environments match; owners often use API 571 alongside their own materials guidelines.
\nPower generation: boiler and steam-system damage such as creep and fatigue is usually addressed through power-industry guidance; API 571 is less commonly the primary reference there, though some mechanisms overlap.
\n\nA: No. Intervals come from API 510, 570 or 653, or from an owner's RBI assessment. API 571 tells you which mechanisms to plan for.
\nA: No. Acceptance comes from the in-service and construction codes; damage beyond those rules may go to an API 579-1 engineering assessment.
\nA: The 3rd edition, March 2020. It reorganised the mechanisms into a single alphabetical section, so paragraph numbers differ from the 2nd edition.
\nA: Yes. API 571 lists common options; the owner selects methods able to find the credible damage, using qualified procedures and personnel. No regulatory approval is needed simply because a method is not listed in API 571.
\nA: NDE technicians are qualified under the employer's written practice (for example ASNT SNT-TC-1A Level II). Authorized inspectors under API 510, 570 or 653 usually hold the matching API certification. The API 571 certification is optional.
\nA: API 571 does not specify. API 510 and API 570 require permanent and progressive records for the equipment.
\n\nAPI 571 is the industry's catalogue of damage mechanisms: use it to decide what can go wrong and how to find it, and use the in-service codes for intervals and acceptance. Atlantis NDT's ASNT Level III consulting supports NDE procedure and technique selection for these programmes.
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