Standardized scalable feet solutions for offshore transformers
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This thesis investigates the design and feasibility of a standardized and scalable support interface (feet system) for offshore power transformers. Offshore transformer installations are exposed to complex combined load conditions, including static mass, platform-induced accelerations, internal electromagnetic vibrations, and transport-related loads. Existing feet solutions are often non‑standardized, installation‑intensive, and prone to issues such as bolt bending, misalignment, and inconsistent vibration performance. The purpose of this work is to develop a modular feet system that improves structural reliability, vibration control, and installation efficiency across a range of transformer sizes.
The study adopts a mixed-methods engineering approach combining literature review, industry input, analytical modelling, and finite element analysis. Two representative transformers within a mass range of approximately 20–85 tonnes are analysed to evaluate the performance of the proposed solution. Numerical simulations are conducted using finite element models, including stress, bolt, modal, and transport analyses, while analytical calculations are used to verify model behaviour and validate key results.
The results demonstrate that the proposed modular feet design provides adequate structural integrity under all investigated load cases in accordance with offshore standards. Stresses in structural components remain within allowable limits, and bolted connections function effectively as friction-based joints when properly preloaded. Modal analysis indicates that the system achieves sufficient separation between natural frequencies and dominant transformer excitation frequencies, enabling effective isolation of high-frequency vibrations while maintaining stability under low-frequency offshore motions. Transport analyses further confirm that dedicated transport supports ensure safe load transfer during handling and shipping operations.
The findings show that the developed feet concept resolves key limitations of existing solutions by reducing bolt bending sensitivity, improving load distribution, and enabling a more standardized and repeatable installation and manufacturing process. The design also supports scalability across different transformer sizes while maintaining consistent performance characteristics. Although the results confirm engineering feasibility, further validation through experimental testing, measurements and detailed fatigue analysis is recommended before full-scale implementation.