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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 h