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Non-Metallic Fitness for Service Journal Article Published

Wed, 12 May, 2021

A feasibility study for fitness-for-service assessments of reinforced thermoplastic pipes has been published in the Inspectioneering Journal. Dr Rob Kulka, the Section Manager of Asset Integrity Management at TWI Ltd, authored the study as part of the work of the NIC.

There are currently no globally-accepted fitness-for-service (FFS) procedures for non-metallic components, leading to the need for an initial roadmap for developing FFS methodologies suitable for pipes in hydrocarbon along with other applications. Dr Kulka’s article was created as a summary of both literature and experience in order to inform future developments in FFS procedure based on possible damage mechanisms.

As the oil and gas industry increasingly looks towards exploration and production from unconventional resources, so new material solutions have been sought for corrosion protection in demanding environments. Reinforced thermoplastic polymer (RTP) pipes have been gaining support as a reliable alternative to traditional carbon steel pipes.

Conventional metallic components have validated FFS procedures under a range of standards and codes in order to assess defects including corrosion damage, cracks, lack of fusion, fatigue damage, misalignment, or other shape defects (perhaps as a result of mechanical damage). An FFS assessment can be used to evaluate the remaining life of the component using operating history, materials degradation, and in-service defect initiation to determine whether a component can safely serve beyond design life, perhaps with modified operating conditions.

Dr Kulka’s study notes that there needs to be more information on the strength characteristics of composites as well as the design specifications of RTPs once subjected to loading conditions. Knowledge of mechanical behaviours, real life loading conditions and performance cases, such as environmental cracking, also needs to be expanded in order to determine flaw tolerances.

In addition, Dr Kulka’s study shows how it may be possible to adapt the FFS techniques from procedures such as API 579-1/ASME FFS-1 from metallic to composite components and their typical damage mechanisms.

You can see a special custom PDF of Dr Kulka’s article, below.

IJ Custom PDF - TWI (MarApr 2021) - pdf - 1mb