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Definition: Fitness for Service (FFS) is the systematic assessment of whether a damaged or defective component can continue to be operated safely. It is based on analytical methods for evaluating corrosion, cracks or wall thickness loss. API 579-1/ASME FFS-1 is particularly internationally recognised.

Practical relevance: The assessment takes into account the damage mechanism, remaining wall thickness, material characteristics, loading and safety factors. Typical types of damage are local corrosion, crack formation or deformation. FFS analyses avoid unnecessary shutdowns, provided that structural integrity has been demonstrated by calculation.

Decision-making perspectives:

• Technical decision-makers: Defining continued-operation, repair or replacement strategies.
• Purchasing/project management: Economic trade-off between repair and replacement investment.
• Science: Application of fracture mechanics models and remaining service life calculations.
• Insurance/law: Demonstrating safe continued use despite documented damage.

Typical testing or verification methods: Wall thickness measurement (UT), fracture mechanics assessment, RBI analysis, materials testing.

FAQ:

• When is a fitness-for-service assessment carried out?
• When damage has been identified and the safe continued use of a component is to be assessed by calculation.

Definition: The fitness-for-service assessment is the systematic evaluation of whether a component or system can be operated permanently in a functional and safe manner under defined operating conditions. It takes into account mechanical, thermal, chemical and tribological loads. The objective is to demonstrate compliance with technical and normative requirements.

Practical relevance: The assessment evaluates load-bearing capacity, deformation behaviour, leak-tightness, corrosion resistance and fatigue strength. It may be based on standards, technical specifications or codes such as the Eurocodes, API standards or the Pressure Equipment Directive 2014/68/EU. The assessment draws on test reports, simulations and operating data.

Decision-making perspectives:

• Technical decision-makers: Approval for continued operation or definition of repair measures.
• Purchasing/project management: Evaluation of performance requirements and contractual warranties.
• Science: Validation of service-life models and load assumptions.
• Insurance/law: Demonstration of intended use and risk minimisation.

Typical testing or verification methods: Mechanical materials testing, non-destructive testing (NDT), FEM simulation, corrosion testing, functional and endurance tests.

FAQ:

• When is a fitness-for-service assessment required?
• In the case of deviations, damage or changed operating conditions, in order to assess safe continued use.