Two men during a Fitness for Service Assessment at a production site, subject to FFS Analysis


Testing, Evaluation, Action

Testing, Evaluation, Action

What is Fitness-for-Service?

Fitness-for-Service (FFS) assessment is a quantitative engineering assessment. The assessment is performed to demonstrate the structural integrity of an in-service component containing a mechanical defect or damage. As such, it can be used to determine if the affected pressure equipment can continue to operate safely for a period of time, thus allowing the opportunity for informed decision-making regarding repairs, replacements, or operational adjustments.


Why are Fitness for Service Assessments important?

In industrial production facilities, various types of critical production assets are subjected to a range of operating conditions and subsequent potential damage mechanisms. Among the critical assets in question are for instance:

  • Pressure vessels – reactors, heat exchangers, collones, separators
  • Piping systems
  • Storage tanks
  • Pipelines
  • Valves and pumps

Over time, these production relevant assets may undergo gradual weakening and develop defects or experience degradation due to factors such as corrosion, fatigue, cracking, erosion, pitting or other damage mechanisms. The FFS assessment is performed to evaluate the impact of these defects or damages on the structural integrity, safety and remaining useful life of the equipment. It involves a systematic analysis that considers the type, size, location and characteristics of the flaws, as well as the operating conditions and applied loads on the equipment and the equipment-specific geometry.

The assessment follows relevant industry codes, standards, and guidelines to determine whether the equipment can continue to operate safely or whether repair, replacement or mitigation measures are required. It helps industry decision-makers make informed decisions about the operation, maintenance, and reliability of equipment, ensuring the overall safety and efficiency of industrial processes.


Why you should choose TÜV SÜD for FFS Assessments

In all our assessments we aim to deliver results within a short timeframe, ensuring the use of appropriate calculation methods and considering all relevant factors that may affect the assessment. If required, we are prepared to use more complex calculation methods to ensure accuracy and thoroughness.

To analyse cracks or crack-like flaws or defects within a weld, a fracture mechanics analysis must be carried out. For this type of analysis, TÜV SÜD gathered experience in +30 years. We offer analytical determinations and, where appropriate, numerical analysis considering cracks.

Your advantages when choosing TÜV SÜD:

  1. Fast response and results through Level 1 analysis (TÜV SÜD uses its own software and keeps it up to date with current codes), this analysis gives answers to the state of integrity and the remaining life
  2. Experts (senior engineers) and numerical tools (FEA) to perform more complex analysis up to Level 3
  3. Our inspectors are all multidisciplinary trained in various classic and Advanced NDT disciplines, PED, various API and ASME codes, RBI and pressure vessel codes; the combination of this knowledge and ongoing training results in reliable work and helpful recommendations for our clients.
  4. Wherever you are in the world. We are probably just a step away from your industrial facilities. We have global matrix organization encompassing all regions of the world and over 75 countries. Clients benefit from a standardized FFS Assessments and corresponding reporting quality and format everywhere in the globe. In addition, the FFS-Assessments can be offered in combination with other inspection on the plant.



Our key goal is to unlock the potential of our client´s assets and ensuring their continued safe operation. With our advanced expertise in Fitness-For-Service (FFS) assessments, we go above and beyond to deliver exceptional solutions tailored to your unique needs.

At the core of our FFS assessments is our proprietary software, a powerful tool compliant with the leading-industry standard and international code API 579-1 / ASME FFS-1.  This cutting-edge software enables us to perform thorough FSS evaluations, to compute the remaining life and provide precise recommendations for safe operations.

What sets us apart is not just our software, but also our team of certified and highly experienced engineers who are deeply engaged in FFS assessments worldwide. With their extensive knowledge and hands-on experience, they have mastered various situations and have successfully tackled numerous challenges across diverse client sites.

Moreover, our in-house software gives our clients remarkable advantages. It allows us to adapt and customize it to meet the ever-evolving demands of the industry, whether it is addressing newer challenges or working with unconventional (newer) materials. We are committed to staying ahead of the curve and providing innovative solutions for situations that are not common in the industry.



At TÜV SÜD, we have comprehensive integrity analysis coverage for almost all types of damages.. 
Examples of typical damage types covered by our FFS system and our FFS engineers are:

  • Wall thickness reductions (uniform or generalised metal loss, localised metal loss on ID (inner or outer surface or OD, pitting)
  • Cracks (surface or internal)
  • Welding anomalies (crack-like defects)
  • Geometric discontinuities (misalignment, roundness, bulges, dents, gouges, weld offsets...)
  • Deterioration of material properties (hydrogen embrittlement (HIC, SOHIC) and / or temper embrittlement, aging, creep...)
  • Operational variations (pressure, temperature, cyclic loading -– fatigue, ...)
  • Laminations

We work according to the international code API 579-1 / ASME FFS-1 “Fitness-For-Service” published by API and ASME.
Depending on the level of complexity in each situation, we distinguish between Level 1 to Level 3 required and we do so always in accordance with API 579-1 / ASME FFS-1.

  • Level 1

    Basic assessment using simplified but very well defined and formulated quantitative methods to quickly evaluate the fitness for service. Level 1 is used for initial screening or when limited information is available.

  • Level 2

    Intermediate assessment involving more detailed analysis and consideration of specific factors. We apply it when more accurate evaluations are required or when specific defects or damages rise specific concerns about the equipment's condition.

  • Level 3

    Advanced assessment employing complex analysis techniques such as finite element analysis and extensive and more detailed NDT data collection. We apply level 3 for highly critical components, complex damage scenarios, or when in-depth analysis and very precise calculations are necessary to ensure safety and reliability. Customers benefit from code compliant and additional tailor made advanced computational algorithms.


We harness the power of advanced finite elemnent models to analyze and optimize complex systems, ensuring realiability and efficiency in every design. 


Get in Touch with TÜV SÜD for your FFS Assessment.



Optimising Maintenance with Fitness-For-Service Assessment