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 equipment damage.

As such, it can be used to determine if the affected pressure equipment can continue to operate safely for a period of time. This gives you the opportunity to make informed decisions on repairs, replacements or operational adjustments.

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

• 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, creep, embrittlement, cracking, erosion, pitting or other damage mechanisms. An FFS assessment evaluates the impact of these defects or damages on the structural integrity, safety and remaining useful life of the equipment. It systematically analyses 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 FFS assessment follows relevant industry codes, standards, and guidelines to determine whether the equipment can continue to operate safely and for how long or whether you need repair, replacement or mitigation measures. It helps you make informed decisions about the operation, maintenance, and reliability of equipment, ensuring the overall safety and efficiency of industrial processes. Determining the remaining lifetime of equipment it furthermore can help to increase the sustainability of industrial plants.

TÜV SÜD has decades of experience in industrial safety. With extensive knowledge and hands-on experience, our experts have mastered various situations and have successfully tackled numerous challenges across diverse client sites. 

Our experts are all multidisciplinary. They are trained in various classic and Advanced NDT disciplines, PED, various API and ASME codes, RBI and pressure vessel codes. This expertise results in reliable work and helpful recommendations for our clients. 

In all our assessments, we aim to deliver fast results. We use our own software and keep it up to date with current codes. We employ appropriate calculation methods and consider all relevant factors that may affect the assessment. If required, we can 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. We offer analytical determinations therefore and, where appropriate, numerical analysis considering cracks. 

Wherever you are in the world, we are just a step away from your industrial facilities. We are a global organisation encompassing all regions of the world and over 75 countries. You stand to benefit from a standardised FFS assessments and corresponding reporting quality and format everywhere. In addition, we can offer the FFS assessments in combination with other inspections of the plant. 

Our in-house software gives our clients remarkable advantages. We can adapt and customise it to meet ever-evolving industry demands, such as addressing newer challenges and working with unconventional (newer) materials. We are committed to staying ahead of the curve and providing innovative solutions for uncommon situations.

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

We assess a wide range of damages via an FFS assessment. These include:

• Wall thickness reductions (uniform or generalised metal loss, localised metal loss on inner or outer surface or  pitting corrosion)
• 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. We do so in accordance with API 579-1 / ASME FFS-1. Our experts (senior engineers) and numerical tools (FEA) perform more complex analysis up to Level 3. 

Level 1: 
Basic assessment using simplified but 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 we need more accurate evaluations or when there are concerns about specific defects and equipment damage. 

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 are also well-versed in the following methods:

Endoscopy to identify cracks. 

Finite Element Models to determine stress distribution.

Numerical Fracture Mechanics to assess the interaction of two neighbouring cracks.