Life Extension — Structural Integrity — Fatigue Strength — Ultrasonic Peening
We are pioneers in our field. In 2005 we were the first company in the world to execute a structural life extension project with ultrasonic peening on a producing offshore installation. The ultrasonic peening or ultrasonic impact treatment has been used to enhance the fatigue strength of welded connections since 1970. What we did is to introduce this fatigue strength enhancement and relate it to a desired life extension of an offshore installation in order to maintain the structural integrity during the remaining service life. In 2005 it did not exist a way to enhance the fatigue strength of welded connections in-situ offshore which could avoid hot-work, which is a determinant issue when it comes to structural maintenance work on oil & gas producing offshore installations. Furthermore, in 2005 within the offshore industry it was not so widespread as it is currently, concepts like life extension, risk based inspection, structural integrity management, etc. As the graphic below shows, the number of FPSO installations is constantly increasing and so it increases also the number of these installations reaching their design service life. Furthermore, many of the currently operating FPSO’s are converted tankers, VLCC or ULCC, which have already served many years as trading tankers.
LETS Global is an internationally known and respected provider of life extension services for the offshore industry. We have successfully executed a number of life extension projects in-situ in offshore installations on the North Sea, Gulf of Mexico and on the coast of Brazil . We continue to do our utmost to exceed our customers’ expectations.
Structural Integrity — Ultrasonic Peening
LETS Global is a pioneering company in the field relating the fatigue strength of elements of structural integrity significance to the concept of structural life extension. Henceforth, the concept service life extension and increased fatigue strength of fatigue sensitive connections in any offshore structure are interlocked and depending of each other. As a result the structural life extension of any offshore structure subjected to fatigue loads will be determined by the increased fatigue strength of these sensitive fatigue hot-spots. The increased fatigue strength can be achieved by the selective ultrasonic peening treatment of weld connections of structural integrity concern.
Whereas the general service life extension of an offshore installation depends on a large number of sensitive sub-structures, process equipment (on-board and surrounding) among many others the structural integrity of the steel structure is of paramount importance. The hull integrity cannot be compromised under any circumstances.
Ultrasonic Peening ensures the crack initiation point is away from high risk areas
The principal methodology when applying ultrasonic peening is to remove the potential fatigue crack initiation as far away from the main deck as feasible, being main deck the top side of crude oil cargo tank in a FPSO installation. Therefore Ultrasonic Peening is used on these welds to ensure fatigue crack would not occur where the consequences for a fatigue crack could be the stop of production. Keeping in mind that among others a life extension project focuses on ways to minimize the risk of any unexpected failure, for example fatigue cracks and a subsequent hydrocarbon’s gas leak, ultrasonic peening can contribute to increased safety in a risk based structural maintenance approach.
Life Extension — Increased Fatigue Strength — Ultrasonic Peening
It’s a very well known fact, weld connections always represent the weakest link from a structural integrity point of view in any welded structure subjected to fluctuating loads, commonly known as fatigue loads. However, far from all welded connections are of structural integrity significance. LETS Global contributes to make the selection of significant welds and to which extent the ultrasonic peening treatment would need to be applied to them.
Ultrasonic peening to maintain the structural integrity
There are several reasons as to why a weld connection can be in need of enhancement of its fatigue strength. Among these could be it had reached their fatigue design life, poor weld quality, unexpected overloads (static or dynamic), need of increased safety design margins to just name a few. The main task will be always to avoid fatigue cracking and by that elude expensive hot-work operations offshore.
Ultrasonic peening and risk based Structural Integrity Management
Hence, a method as ultrasonic peening, to prevent fatigue cracking in an operating offshore installations is highly desirable. In any risk based Structural Integrity Management system the lowest possible risk for any structural damage will be much sought-after. Ultrasonic peening increases the resistance against fatigue cracking in welds with high risk for cracking and therefore it will contribute to the overall safety of the installation.
Ultrasonic peening and life extension
The fatigue strength improvement achieved by the ultrasonic peening treatment on the weakest points in any offshore installation can make possible to extend the structural service life of the structure. So with a relatively small investment in maintenance work the contributions to the overall safety and structural integrity could be substantial.
10 years of ultrasonic peening offshore experience
We have been offering and performing the ultrasonic peening treatment offshore and onshore for more than ten years. That is our best advertisement and references to new customers who are still discovering the advantages of this technology combined with our long experience in the field.
The foundation of LETS Global was laid by our Technical Director Luis Lopez Martinez, with more than 30 years experience with structural fatigue and offshore structures. We aspire to attract long-term structural life extension projects with the aim to safeguard structural integrity of assets while avoiding conventional weld-repair methods.