Introduction to API 579 / ASME FFS-1 Fitness For Service (FFS)

API 579-1/ASME FFS-1 Fitness for Service on Ash Silo

Introduction to API 579 / ASME FFS-1 Fitness-For-Service (FFS) 

Keywords: API 579 / ASME FFS-1; Fitness for Service; FFS; ASME FFS; Asset Life Extension; Remaining Life

API 579 / ASME FFS-1 Fitness-For-Service (FFS) is performed to ensure equipment structural integrity when a flaw or damage occurs. This standard provides guidance for conducting FFS assessments, specifically prepared for pressurized equipment. Inspections of a pressure vessel, tank, or related equipment should be performed on a regular basis to ensure their continued operation is safe.

Fitness-for-service evaluations performed in accordance with this Standard are recognized and referenced by API 510 (Pressure Vessel Inspection Code), API 570 (Piping Inspection Code), API 653 (Tank Inspection, Repair, Alteration, and Reconstruction), and by NB-23 (National Board Inspection Code) as suitable for evaluating the structural integrity of pressure vessels and related equipment.


Ensuring the safety and reliability of equipment in plants such as refineries, chemical plants, and power plants is of paramount importance. These plants operate under extreme conditions (pressures, temperatures, etc.), which leads to potential degradation and damage to their components over time. To address these concerns, the American Petroleum Institute (API) and the American Society of Mechanical Engineers (ASME) developed the API 579 / ASME FFS-1 Fitness-for-Service standard.

This standard provides a comprehensive framework for assessing the fitness-for-service of components and structures that are subject to degradation, such as corrosion, cracking, or mechanical damage. It outlines procedures and methodologies to evaluate the structural integrity and remaining life of equipment, ensuring their safe and continued operation.

The standard offers several benefits and has widespread applications across various industries:
Safety Assurance: By providing a systematic approach to evaluating the fitness-for-service of equipment and structures, the standard ensures that potential risks are identified and mitigated. This leads to improved safety and reduced chances of catastrophic failures, protecting personnel, the environment, and assets.
Life Extension: The standard enables engineers to assess the remaining life of components, allowing for optimized maintenance strategies. This extends the operational lifespan of equipment, leading to cost savings and reduced downtime.
Risk-Based Inspection (RBI): API 579 / ASME FFS-1 can be integrated into RBI programs, where inspection intervals are determined based on the assessed risk of failure. This approach optimizes inspection resources and prioritizes critical components, resulting in more efficient maintenance practices.

Historical Background of API 579 / ASME FFS-1

1990: Joint industry project was organized by the Materials Properties Council (MPC) to develop FFS guidelines for the refining industry
2000: Based on the MPC final report, API issued API-579 recommended practice for FFS Assessment, which was welcomed by both refinery and non-refinery industries
2007: ASME joined forces with API and issued API 579 / ASME FFS-1

Parts of the (2000) API 579 / ASME FFS-1

1 – Introduction
2 – FFS Engineering Evaluation Procedure
3 – Brittle Fracture
4 – General Metal Loss
5 – Localized Metal Loss
6 – Pitting Corrosion
7 – Blisters, HIC, and SOHIC Damage
8 – Weld Misalignment and Shell Distortions
9 – Crack-Like Flaws
10 – Equipment Operating in the Creep Range
11 – Fire Damage


(1) “An Overview of API 579-1/ASME FFS-1 Fitness-For-Service Assessment Standard with Applications to Case Studies” Mohammad M. Megahed & Mohammad S. Attia, Faculty of Engineering – Cairo University – Egypt, 3rd International Conference in Africa and Asia, Welding and Failure Analysis of Engineering Materials, 2-5 November 2015, Luxor, Egypt
(2) Fitness-For-Service Assessment Procedures API 579/BS 7910 (
(3) M. G. Gruenefeld, “API 579-1 / ASME FFS-1 Fitness-for-Service Evaluations,” Materials Performance, vol. 47, No. 3, pp. 34-39, Mar. 2008
(4) R. P. Lewis, “Overview of the Fitness-for-Service Assessment Procedures in API 579-1 / ASME FFS-1,” Journal of Pressure Vessel Technology, vol. 128, no. 4, pp. 461-466, Oct. 2006

Resources on Fitness for Service

API 579: A Comprehensive Fitness-For-Service Guide (International Journal of Pressure Vessels and Piping)

Image of Ash Silo for API 579-1 / ASME-1 Fitness for Service

We performed an API 579 / ASME FFS-1 Fitness For Service Evaluation of a 40 year old ash silo (approximately 38-foot diameter x 64-foot tall).

In addition to performing Fitness for Service Evaluations – we also provide engineering to API Codes including 510, 570, 653.

See Also:

– API / ASME-1 579 Fitness For Service on a Brewery Tank
– API / ASME-1 579 Fitness For Service on a Urea Reactor
– “Quantifying Fitness For Service” Article by Bill O’Donnell, Sr.

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