Fitness-For-Service (FFS) assessments are quantitative engineering evaluations that are performed to demonstrate the structural integrity of an in-service component that may contain a flaw or damage.

This Standard provides guidance for conducting FFS assessments using methodologies specifically prepared for pressurized equipment.

The guidelines provided in this Standard can be used to make run-repair-replace decisions to help determine if pressurized equipment containing flaws that have been identified by inspection can continue to operate safely for some period of time. These FFS assessments are currently recognized and referenced by the API Codes and Standards and by NB-23 as suitable means for evaluating the structural integrity of pressure vessels, piping systems and storage tanks where inspection has revealed degradation and flaws in the equipment.

The popularity of FFS approach is   that it save money and leads to more safety While other codes follow calendar based inspection, FFS  taken from RBI also as the result more accurate inspection can be  done