Fatigue Lifetime Assurance with Monitas
MARIN is completing a specification and pilot application Joint Industry Project (JIP) of advisory hull monitoring systems for FPSOs. Report provides an update.
Mirek Kaminski,
m.kaminski@marin.nl
Four years ago in Report 88, MARIN announced that a specification and pilot application JIP for advisory monitoring systems for FPSOs had been launched. The project was named Monitas, which stands for Monitoring Advi-
sory System. Today we are pleased to report that the project goals have been successfully realised and that the JIP team has decided to go ahead with linking the Monitas system with Risk Based Inspections.
The Monitas JIP is supported by many major oil and gas companies including Chevron, Petrobras, Shell and Total, major class socie- ties (ABS, BV, DNV, KR and LR), FPSO design- ers (Bluewater and SBM), and shipyards (IHI-Marine United, Kawaski and Samsung). Recently, Amarcon joined and it will develop the Octopus-Monitas software that will be delivered to the Monitas participants soon. Chaired by Didier L’Hostis of Total, the project is carried out by MARIN in cooperation with Bluewater, WaveForce Technology and Amarcon.
Didier l’Hostis (Total), Chairman of Monitas: “The project demonstrated that the Monitas system gives meaningful results for an existing FPSO. For a newly built FPSO we have already learned that the system and the structure have to be designed at the same time. This is what we expect to verify when we get the newly built FPSO results in phase 2.”
Monitas advises on fatigue lifetime consump- tion based on the fatigue design data, fatigue design tool and the monitoring data of hull girder loads, global and local stresses, wave frequency motions, ship’s loading condition/ heading and the environmental conditions. In contrary to conventional structural health monitoring systems estimating the actual fatigue lifetime consumption, the system explains potential deviations from design assumptions. In this way the Monitas system provides designers with feedback about the quality of their design tools including the assumptions made and it advises the FPSO operators on actions required to ensure a safe operation. If needed, this advice can be used to justify lifetime extension. In the JIP the pilot application was devel- oped, installed and tested for two years onboard the Glas Dowr FPSO. The challenge was to reduce the required sensors to a minimum and to process the data into simple graphs showing the actual consumed fatigue lifetime against the design values. This not only provides essential feedback for designers but also provides a good basis for inspection and maintenance offshore. This is particularly relevant for moored FPSOs but also for the fatigue life assessment of units that are re-located to new fields.
During the OTC 2010, a special session devoted to the Monitas achievements will be organised and five papers will be presented (see news section). More infor- mation about Monitas can be found at
www.marin.nl and
www.fpsoforum.com.
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