What is meant by Fitness for Service?

Fitness for Service (FFS) assessments help determine if equipment is safe and fit for continued operation. It prevents breakdowns, minimizes risk and avoids costly repairs.

Assessment procedures are used by the oil and gas, hydrogen, power generation and chemical processing sectors for integrity management and to assess the suitability for use of pressurized equipment.

Engineering companies can assess the structural and mechanical integrity of a wide range of components according to international standards API 579-1/ASME FFS-1, including boiler, HRSG, pressure vessels, chemical reactors, storage tanks, piping systems and pipelines.

From design to decommissioning, Fitness for Service assessments help prevent brittle and ductile fractures and metal loss, make cost-effective run-repair-replace decisions, and resolve problems that may arise during a component's life.

Assessments according to API 579/ASME FFS-1

This standard provides guidance for conducting fitness-for-service assessments using methodologies specifically prepared for pressurized equipment. Fitness-for-service assessments are quantitative engineering evaluations that are performed to demonstrate the structural integrity of in-service components that may contain a flaw or damage, or that may be operating under a specific condition that might cause a failure.

The guidelines provided in this standard can be used to make run-repair-replace decisions to help determine if components in pressurized equipment containing flaws that have been identified by inspection can continue to operate safely for some period of time.

These fitness-for-service assessments are currently recognized and referenced by API codes and standards (510, 570, and 653), and by NB-23 (National Board Inspection Code) as suitable means for evaluating the structural integrity of pressure vessels, piping systems, and storage tanks where inspection has revealed some level of degradation and/or flaws in the equipment.

This standard was developed by a joint API-ASME committee, is an ANSI American National Standard, and is recognized as an International Code.

Equipment may be defective, damaged, or aging so that it cannot be evaluated against the original construction codes. API 579-1/ASME FFS1 can be used to assess equipment for continued use. It allows..

Thermomechanical analysis under operating conditions (temperature and strain): normal operating conditions, transients, predictable exceptional or faulty operating conditions.
Structural analysis under normal operating conditions aimed at detecting anomalies (thickness reduction due to corrosion/erosion, subsidence/displacement of supports/anchors) to evaluate continued use and the need for any corrective measures.
Design, design verification, assessment of defective components and requalification.
Evaluation of defect propagation rate and stability assessment for operating conditions according to recognized procedures and standards (API 579, BS 7910 etc.).
Evaluation of structural inspection results and assessment of severity of defects detected.
Assist in failure analysis studies and evaluation of the plausibility of a failure scenario.

FFS assessments are performed on a wide range of products, including..

Heat recovery boilers and steam generators (headers, vessels, etc.).
Pipelines (water/steam/gas lines, process lines, pipes, etc.).
Turbine (rotors and casing)
Other plant components (pressure vessels, valves, piping, tubes, furnaces, reactors, heat exchangers, storage tanks, etc.).