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

The main focus of Fitness-For-Service analysis is evaluating whether an equipment has downgraded in service and can carry on its intended function properly. This approach comprises in a rational decision process, enabling the engineer to decide whether the system can be controlled safely either as is, with reinforced inspection, after a requalification, or after a service or repair.

A process, plant, and equipment are often exposed to corrosive environments and/or elevated temperatures. Under these conditions, the material used in the equipment can degrade or age with time. When important equipment such as pressure vessels, piping, and storage tanks become older, the plant operator must decide if they can continue to operate safely and reliably to avoid injuries to personnel and public, damage the environment, and cause unexpected shutdowns. Fitness for service assessment procedures provide the means for the plant operator to make appropriate decisions on established engineering principles.


Fitness for service assessment is a multidisciplinary engineering analysis that ensures all process and plant equipment such as pressure vessels, piping, and tanks operate safely and reliably for the desired period of operation and until the next turnaround or planned shutdown occurs in the future. ASME, API, BS 5500 & other recognized design codes provide rules/guidelines for a general procedure for assessing fitness for service. This assessment procedure evaluates the remaining strength of the equipment in its current state that may have degraded from its original condition. Common degradation mechanisms include corrosion, localized corrosion, pitting and crevice corrosion, hydrogen attack, embrittlement, fatigue, high-temperature creep, and mechanical distortion.


Overview of API 579/ASME FFS-1 - Fitness-For-Service (FFS)

API 579/ASME FFS-1, Fitness-For-Service, Third Edition, is a standard developed and published jointly by the American Petroleum Institute (API) and ASME. It describes several fitness-for-service (FFS) assessment techniques that help ensure the safe and reliable operation of pressurized equipment used in oil & gas, petrochemical, and chemical facilities.


API 579/ASME FFS-1 provides procedures for performing proper fitness-for-service assessments and/or rerating of equipment that is designed and constructed to recognized codes and standards. This standard contains numerous sections on assessment procedures for calculating the impact of damage mechanisms such as brittle fracture, general metal loss and local metal loss, pitting corrosion, blisters and laminations, weld misalignment and shell distortion, crack-like flaws, creep damage, and fire damage.


This standard has procedures for evaluating several different types of equipment (pressure vessels, piping, and tankage) that may contain flaws or damage. These include the evaluation and rerating of pressure vessels designed based on the the ASME Boiler and Pressure