Managing the integrity of ageing assets is a complex task. The inspection and assessment of defects requires the operator to interface with several subcontractors in order to execute pre-inspection cleaning, screening inspections, detailed sizing inspections and assessment calculations. To make this process more efficient and effective, Proserve, Innospection, Sonomatic and Atkins have formed an alliance that delivers our combined services through a single interface.

When a defect or damage is initially discovered then a staged assessment process is usually followed:

1. Initial UT or MPI results are assessed using a Level 1 or Level 2 approach as defined in API RP579.
2. If the above does not demonstrate that the component is fit for service then more detailed NDT can be performed and assessed to API RP579 Level 3. The Level 3 assessment is much more accurate than level 1 or 2 but takes slightly longer to perform due to the more complex calculation.

A Level 3 assessment to API RP579 is critically dependant on high quality NDT results that are properly interpreted. For these reasons Atkins has recently worked in close cooperation with Sonomatic to provide a unified delivery of fitness for service assessments.

The figures below shows wall thickness mapping performed by Sonomatic on a pig launcher with internal erosion and the plastic strain calculations by Atkins using a non-linear finite element calculation in accordance with API RP579. This Level 3 assessment demonstrated that the pressure system was fit for service and avoided an unplanned shutdown to affect a repair.

Atkins has significant experience of fitness for service assessments for plant on fixed and floating offshore installations and onshore facilities including pressure vessels, pipelines and process pipe work, flanges and nozzles.

Assessments for corrosion, cracking, weld root erosion, fatigue and vibration have all been performed.

The Level 3 assessments offered by Atkins are founded on expertise and indepth understanding of the fundamentals:

• Advanced non-linear FE analysis methods
• Stress analysis and mechanics of solids
• Safety and risk (probability and consequence)
• Fatigue and Reliability
• Fracture Mechanics
• Anomaly and defect assessment
• Remedial Measures design
• Application of API RP579

In addition to Level 3 assessments, Atkins also has the capability to carry out analysis to establish local loading  conditions where this may be required. This can take the form of vessel calculations to, for example, BS PD 5500 or ASME VIII, or by performing pipe stress analysis to recognised design codes.

Following the assessment, Atkins can also advise on remedial measures or inspection requirements going forward.

Contact Us

For enquiries or further information contact Ramsay Fraser direct on 01224 264342.