Methodology for the structural analysis of a main deck of FPSO vessel supporting an offshore crane

Offshore cranes placed on the surface of Floating Production Storage and Offloading (FPSO) vessels affect the structural response of their main decks, which can alter the safe operation of the FPSO vessels. Generally, classification societies rules are used to predict the structural strength of the main deck of FPSO vessels. However, these classification societies rules are limited to estimate the variation of the structural performance of the main deck caused by the operation of offshore cranes under different hydrodynamic conditions. Here, we present a methodology to determine the alteration of the structural behavior of a main deck of FPSO vessel due to different operation conditions of a board offshore crane. This methodology considers the hydrodynamic response for two ultimate limit states: operating and storm conditions from 1000 m water depth in Gulf of Mexico with a return period of 10 and 100 years, respectively. The methodology includes finite element method (FEM) models of the main deck supporting an offshore crane to predict its structural response. The maximum von Mises stress of the main deck does not overcome its maximum permissible stress, which allows a safe operation of the FPSO crane. The proposed methodology can be used to estimate the structural behavior of main decks of FPSO vessels that are modified for supporting offshore cranes, regarding the hydrodynamic response for each FPSO under the operation and extreme conditions in its location. Thus, naval designers could select the better structural modifications of the main decks that decrease their costs of construction and maintenance.

Análisis aerodinámico de un vehículo aéreo no tripulado con forma de halcón para monitoreo de fugas de hidrocarburos

The oil pipeline network requires periodic monitoring to detect pipeline damages, which may cause oil leakage with severe environmental contamination. These damages can be generated by interference from third parties such as construction works, sabotage, vandalism, excavations, and illegal oil theft. To detect the oil pipeline damages, it can be used aerodynamic aerial vehicles (UAVs) with infrared cameras and image processing systems. This paper presents the aerodynamic analysis of a UAV with a hawk shape (wingspan of 2.20 m and length of 1.49 m) for potential application in the detection of oil pipeline failures. A 1:6.5 scale prototype of the UAV is fabricated using a 3D printer. The aerodynamic coefficients of UAV are determined using computational fluid dynamic (CFD) simulations and experimental testing with a subsonic wind tunnel. In addition, the lift and drag coefficients of UAVs are obtained as a function of Reynolds number and angle of attack. Also, the air velocity profile around UAV is estimated with the CFD model. The proposed UAV could decrease the inspection costs of pipeline networks in comparison with the use of helicopters or light aircraft.La red de oleoductos requiere monitoreo periódico para detectar daños que puedan causar fugas de hidrocarburos con severo daño ambiental. Estos daños pueden generarse por interferencia de terceros, tales como trabajos de construcción, sabotaje, vandalismo, excavaciones y sustracción ilegal de hidrocarburos. Para detectar daños en oleoductos pueden utilizarse vehículos aéreos no tripulados (UAVs) con cámaras infrarrojas y sistemas de procesamiento de imágenes. Este trabajo presenta el análisis aerodinámico de un UAV con forma de halcón (envergadura de 2,20 m y longitud de 1,49 m) para aplicación potencial en la detección de fallas de oleoductos. Un prototipo a escala de 1:6,5 es fabricado usando una impresora 3D. Los coeficientes aerodinámicos del UAV son determinados usando simulaciones de dinámica de fluidos computacionales (CFD) y pruebas experimentales con un túnel de viento subsónico. Además, los coeficientes de sustentación y arrastre del UAV son obtenidos como función del número de Reynolds y el ángulo de ataque. También, el perfil de velocidad del aire alrededor del UAV es estimado con el modelo CFD. El UAV propuesto podría disminuir los costos de inspección de oleoductos en comparación con el uso de helicópteros o vehículos aéreos ligeros

Análisis estructural de la cubierta principal de un buque de apoyo a plataformas con una grúa sobre orugas

Support vessels for platforms in the oil industry have operation versatility and capacity for structural modification. This article presents a proposal for the installation of a crawler crane on the main deck of a platform support vessel, which will carry out offshore maintenance operations. This proposal includes the results of the structural analysis of the main deck, considering its reinforcement with two NVA36 beams. This structural analysis incorporates the integrity of the main deck, taking into account the crane and loads through finite element method (FEM) models. The obtained results show that the main deck requires the proposed reinforcement to decrease the maximum stresses of von Mises up to 218.71 MPa for the structure of the main deck and 201.67 MPa for the reinforcement beams. These maximum stresses do not exceed the allowable and yield stresses of the main deck material. The reinforcement of the main deck that supports crawler crane allows safe operation of the offshore support vessel.Los buques de apoyo para plataformas de la industria petrolera tienen versatilidad de operación y capacidad de modificación estructural. Este artículo presenta una propuesta de instalación de una grúa sobre orugas sobre la cubierta principal de un buque de apoyo a plataformas petroleras, el cual realizará operaciones de mantenimiento en mar adentro. Esta propuesta incluye los resultados del análisis estructural de la cubierta principal, donde se considera el refuerzo con dos vigas NVA36. Este análisis estructural incorpora la integridad de la cubierta principal considerando la grúa y las cargas mediante modelos del método de elementos finitos (MEF). Los resultados obtenidos muestran que la cubierta principal requiere el refuerzo propuesto para disminuir las tensiones máximas de Von Mises hasta 218,71 MPa para la estructura de la cubierta principal y 201,67 MPa en las vigas de refuerzo. Estas tensiones máximas no superan las tensiones admisibles y de fluencia del material de la cubierta principal. El refuerzo de la cubierta principal que soporta la grúa sobre orugas permite la operación segura del buque de apoyo mar adentro.

Numerical Predictions of a Swirl Combustor Using Complex Chemistry Fueled with Ammonia/Hydrogen Blends

Ammonia, a chemical that contains high hydrogen quantities, has been presented as a candidate for the production of clean power generation and aerospace propulsion. Although ammonia can deliver more hydrogen per unit volume than liquid hydrogen itself, the use of ammonia in combustion systems comes with the detrimental production of nitrogen oxides, which are emissions that have up to 300 times the greenhouse potential of carbon dioxide. This factor, combined with the lower energy density of ammonia, makes new studies crucial to enable the use of the molecule through methods that reduce emissions whilst ensuring that enough power is produced to support high-energy intensive applications. Thus, this paper presents a numerical study based on the use of novel reaction models employed to characterize ammonia combustion systems. The models are used to obtain Reynolds Averaged Navier-Stokes (RANS) simulations via Star-CCM+ with complex chemistry of a 70%–30% (mol) ammonia–hydrogen blend that is currently under investigations elsewhere. A fixed equivalence ratio (1.2), medium swirl (0.8), and confined conditions are employed to determine the flame and species propagation at various operating atmospheres and temperature inlet values. The study is then expanded to high inlet temperatures, high pressures, and high flowrates at different confinement boundary conditions. The results denote how the production of NOx emissions remains stable and under 400 ppm, whilst higher concentrations of both hydrogen and unreacted ammonia are found in the flue gases under high power conditions. The reduction of heat losses (thus higher temperature boundary conditions) has a crucial impact on further destruction of ammonia post-flame, with a raise in hydrogen, water, and nitrogen through the system, thus presenting an opportunity of combustion efficiency improvement of this blend by reducing heat losses. Final discussions are presented as a method to raise power whilst employing ammonia for gas turbine systems