ROV systems and preliminary design of a cage type TMS

The thesis provides an overview of ROVs within offshore engineering field and develops a preliminary structural assessment of a representative Tether Management System (TMS). After outlining the evolution, classification and operational roles of modern work-class ROVs, the study examines the architecture of complete ROV architecture including tether and umbilical systems, TMS units and launch-and-recovery equipment. The technical core focuses on the preliminary structural design of a TMS inspired by the Seaeye TMS8. The main load-bearing members were reconstructed from available drawings and idealised through a simplified beam-element model. Loads derived from self-weight, ROV mass and DNV dynamic amplification factors were applied to evaluate the governing effects on bending, shear, axial forces and buckling. Verifications included shear checks near the lifting point, deflection analysis using Euler–Bernoulli theory, material stress assessment through both Allowable Stress Design and Limit State Theory, and column stability evaluation through buckling analysis. A comparative finite element study using Fusion 360 and SAP2000 was performed to validate and complement the analytical results. Fusion 360 captured local stress concentrations and the stiffening contribution of the central lifting plate, while SAP2000, relying on beam-element formulation produced more realistic predictions of global stiffness and load paths. Differences in deflection and stress distribution were traced back to modelling assumptions, element types and joint idealisation, reinforcing the value of a dual-software approach. Overall, the study shows that a rational preliminary design can be achieved without a full 3D detailed model, provided that appropriate engineering simplifications are adopted. The methodology developed forms a solid foundation for future refinement using advanced FEM analyses or manufacturer data.