Papers by Keyword: Offshore

Abstract: This work aimed to develop new S355-based structural steels with enhanced marine corrosion resistance while preserving mechanical properties. Two alloying strategies (Cu/Ni and Al/Cr) were investigated. Conventional and new steel samples were produced and characterized for microstructure, mechanical properties, and corrosion. The new steels showed similar or improved mechanical properties. Potentiodynamic polarization tests indicated stabilization of the oxidation process in the new steels. Laboratory accelerated corrosion tests on painted specimens revealed reduced blistering at paint film defects for some new steels compared to conventional steel. Ongoing research includes evaluating painted specimens in a real offshore environment using an advanced floating laboratory

Abstract: The application of tuned mass dampers (TMDs) to offshore wind turbines has a huge potential to suppress the large vibration responses of these systems. Control module of TMDs is added into the wind turbine structural dynamics simulation code FAST and fully coupled aero-hydro-TMD-structural dynamics model of the 5MW Barge-type floating wind turbine by National Renewable Energy Laboratory (NREL) is established. A multi-parameter optimization study is performed to determine the optimal parameters of a fore-aft TMD system in the Barge-type model. The wind turbine model equipped with the optimal TMD is then simulated under five typical load conditions and the performance of the new system is evaluated. The results show that longitudinal loads at tower base and deflections at tower top reductions of up to 50% and longitudinal loads at blade root and deflections at blade tip reductions of up to 40% are achieved, which indicates that the optimal TMD can be used to suppress the vibration response of offshore wind turbines and also demonstrates the potential for TMD structural control approaches.

Abstract: – The usage of steel in offshore deep water area contributes to the massive load of the offshore platform which will lead to the massive operational cost. Therefore, the reduction of weight of platform is the major issue that need to be tackled properly. The great improvement in strength to weight ratio compare to steel and high resistivity to corrosion makes Glass Fibre Reinforced Polymer (GFRP) grating preferable. GFRP gratings are normally made of two types of processes which are moulded and pultruded and it is usually consists of glass fibre and bonding matrixes of vinyl ester (VE), polyester (PE), or phenolic (PHE). However there is still doubt on GFRP grating application for offshore due to no consensus guidelines for the design of GFRP grating and there are many several types of GFRP grating available to be chosen. This paper presenting the study on two types of GFRP grating strength with variation of bonding matrixes under flexural static load. A total of six specimens of GFRP grating which consist of 1 each of molded vinyl ester, molded polyester, molded phenolic, pultruded vinyl ester, pultruded polyester and pultruded phenolic were tested to failure in flexure. The main parameters concerns in this study are 1) max load vs. mid-span deflection and 2) failure mode of the specimens.

Abstract: To solve problems met in an offshore High-Pressure High-Temperature (HPHT) well testing, a new technology is put forward—placing seal bore extension above permanent packer, and the upper landing tools being connected with seal bore extension through shear pins. This method gives a reverse position of seal bore extension compared with conventional way in which seal bore extension is below permanent packer. So, the feasibility must be considered. Two technological procedures, testing before cutting pins and testing after cutting pins, are discussed, and the highlight is on axial force and deformation of testing string at crucial moments. Results indicate that this new technology is feasible. Of the two technological procedures, axial force is the key factor when testing before cutting pins and axial deformation is the key factor when testing after cutting pins. Conclusions have been used in an offshore HPHT well testing design.

Abstract: Glass Fiber Reinforced Polymer (GFRP) gratings are normally made of two types of processes which are molded and pultruded. It consists of glass fiber and bonding matrixes of vinyl ester (VE), polyester (PE), or phenolic (PHE). The great improvement in strength to weight ratio compare to steel and high resistivity to corrosion makes GFRP grating preferable. However, the use of GFRP grating in offshore is scarce due to issues related to durability and the harsh environment Based on the observation, the accelerated ageing process affects the performance of GFRP gratings by reducing its strength in flexural static load test. Therefore; this study concentrates on the effect of accelerated ageing on GFRP grating. A total of 18 GFRP grating specimens which consist of 6 each of molded Vinyl Ester, molded Polyester and pultruded Phenolic. The entire specimens were aged by immersion in seawater at elevated temperature (60 °C) for the period of 2 month. The main parameters concerns in this study are 1) Max Load vs. Immersion Period, 2) Max Load vs. Deflection graph of results.

Abstract: China has great potential in offshore wind energy and makes an ambitious target for offshore wind power development. Operation and Maintenance (O&M) of offshore wind turbines become more and more important for China wind industry. This study introduces the current offshore wind power projects in China. Donghai Bridge Offshore Demonstration Wind Farm (Donghai Bridge Project) is the first commercial offshore wind power project in China, which was connected to grid in June 2010. O&M of Donghai Bridge Project represent the state-of-the-art of China offshore O&M. During the past two and half years, O&M of Donghai Bridge Project has gone through three phases and stepped into a steady stage. Its believed that analysis of O&M of Donghai Bridge Project is very helpful for Chinas offshore wind power in the future.

Abstract: Compared to nuclear power, wind power has a short construction period, high security, rich in resources and other advantages; compared to photovoltaic power generation, wind power has the power and low cost advantages. Over the past five years, benefit from the support of the localization rate and other policies, the average annual wind power in China compound growth rate of 101%, wind power industry chain upstream parts manufacturing localization, spindle bearings, control systems also need to be imported; midstream machine manufacturing market dominated by domestic-funded enterprises; downstream wind power operators also see five power generation groups, led by the central enterprises the wind turbine increasing unit capacity of 1.5MW and above the level of wind turbine occupy a major share of the market, the development of wind power is inseparable from the support of the policy. Offshore wind power has high feed-in tariff, high throughput advantage of offshore wind power will become a growth point of the wind power industry in the future.

Abstract: Damage Detection problem in Structural Health Monitoring (SHM) is widely studied by many researchers, therefore lots of damage detection algorithms can be found in the literature. Feature Selection / Extraction methods are essential in the accuracy of these algorithms, they provide the suitable data to be used. The main goal of this work is to improve the input data to be the most representative for the damage detection problem. This is done using different Feature Selection / Extraction methods (PCA, UmRMR, and a combination of both). After taking the representative features, the results are tested using a damage detection method; the NullSpace in this case. The data has been collected from a Laboratory Offshore tower model. The different results are compared (different preprocessing vs Raw data) and these show how the correct preselection of the data can improve damage detection.

Abstract: Offshore structures for oil and gas exploitation are subjected to various ocean environmental phenomena which can cause highly nonlinear action effects. Offshore structures should be designed for severe environmental loads and strict requirements should set for the optimum performance. The structural design requirements of an offshore platform subjected to wave induced forces and moments in the jacket can play a major role in the design of the offshore structures. For an economic and reliable design; good estimation of wave loadings are essential. The structure is discretized using the finite element method, wave force is determined according to linearized Morison equation. Hydrodynamic loading on horizontal and vertical tubular members and the dynamic response of fixed offshore structure together with the distribution of displacement, axial force and bending moment along the leg are investigated for regular and extreme conditions, where the structure should keep production capability in conditions of the one year return period wave and must be able to survive the 100 year return period storm conditions. The results show that the nonlinear response analysis is quite crucial for safe design and operation of offshore platform. Fixed Jacket type offshore platforms under extreme wave loading conditions may exhibit significant nonlinear behavior. The effect of current with different angles when hitting the offshore structure with the wave and wind forces, is very important for calculate the stress, the response displacement and deformation shapes. As the current increase or decrease the effect of wave force according to the hitting angle of current.

Abstract: The offshore activities in cold waters have moved from shallow to deep sea waters, which require different operations as compared to activities in hot sea water. Such offshore operations in cold regions like arctic may be effected by the ice accretion on deck and other areas of structure. Ice mainly accretes from both sea spray and atmospheric icing, which can create problems for operational environment and safety of people working on offshore structures in cold regions. In this research a lab based experimental study has been carried out to preliminary design and test an intelligent thermal anti/de-icing system. The experimental study was carried out in cold room chamber of Narvik University College, where temperature can be well controlled between +10 to-30 °C. The proposed intelligent thermal based deicing system can be used to control the communication between icing sensors, weather station, heating devices and central control unit. In this preliminary design phase, a simple surface temperature control method has been developed and tested that can further provides an efficient thermal deicing method and will also be capable to control the surface temperature of objects of interest in cold regions