Maintain structural integrity while extending the service life of offshore rigs.
This is done by means of a comprehensive Life Extension Program approach where the structural integrity sensitive areas are selected and quantified with the help of FE analysis, offshore inspections and the experience of our skilled Naval Architects and Structural Integrity engineers.
When the fatigue sensitive weld connections are located and the target service life selected, LETS Global Life Extension Procedure which includes ultrasonic peening treatment, will ensure a fatigue crack free structure for the remaining service life of the installation.
We also provide advice on FEA model development including sub-modeling and results evaluation, onsite offshore inspection as well as ultrasonic peening treatment.
The efficiency of the Life Extension Procedure as well as the efficiency of the ultrasonic peening treatment is direct related to the correct selection of the areas to be treated as well as the exact extension of the treatment. Therefore special attention should be paid to analysis and palning of the areas to be treated previous to the execution of the treatment.
Life Extension and Ultrasonic Peening
As most of the offshore installations facing any life extension program have consumed at least half of their original design life it is likely some fatigue crack could have developed. Therefore previous to the ultrasonic peening treatment we carry out NDT inspection, MPI or if needed UT, in order to ensure the weld is free of relative deep cracks. If the cracks found are shallow or line cracks along the weld toe, the ultrasonic peening treatment could still restore their fatigue strength up to a level beyond the original design life.
Life Extension Procedure and Ultrasonic Peening
The LETS Global Life Extension procedure has been applied successfully in several offshore installations around the world.
The procedure includes needle-gun cleaning of the weld, ultrasonic peening treatment of weld toes and weld face and if needed weld re-shaping to ensure maximum benefit of the treatment. The treatment of a weld face or multi-pass welds is carried out with the help of a multi-striker peening tool. Subsequently for re-coating we recommend normally a high-strain capacity coating to ensure no coating damage and hence no corrosion damage will occur due to high strains normally present at locations with high stress concentrations.