Dynamic Analysis of Floating Dock Operations with Corrosion-induced Holes at Ballast Tanks

Abstract

The corrosion at the ballast tanks is a concern risk for floating docks that have been in service for several decades. Corrosion events can result in severe accidents and huge economic costs. To migrate the corrosion risk, the dynamic response of a floating dock under corrosion-induced accidents are studied using a numerical method. The numerical model is proposed to calculate the dynamic responses of the floating dock during operations. It includes a six-degree-of freedom (6-DOF) model, a hydrostatic force model, a hydrodynamic force model, a hydraulic model, and a modified P-controller. The hydraulic model is proposed to model the flow through the valves and pumps as well as the corrosion-induced holes. The investigated floating dock is equipped with 18 ballast tanks, which are exposed to corrosion due to the seawater. The influence of the position and the diameter of the corrosion-induced holes on the stability and the dynamic behavior of the floating dock at its work position and during the ballasting and de-ballasting operation are studied numerically using the proposed model. For the corrosion-induced ballasting of the floating dock at its working position, the maximum pitch and roll angles are 0.42 degrees and 2.04 degrees respectively when there are one or two holes located at different tanks. For the automatic ballasting with corrosion-induced holes, the maximum roll and pitch angles during the operations are found to be proportional to hole diameters. With two 300 mm-diameter corrosion-induced holes at different ballast tanks, the present modified P-controller is able to regulate the floating dock's pitch and roll angles within very small ranges. For the automatic de-ballasting with corrosion-induced holes with a diameter of 300mm, the presence of automatic ballast control couldn’t keep all cases within a safe margin because some special locations of the corrosion-induced holes cause large trim and roll moments. This analysis can emphasize the potential hazards of the corrosion-induced holes and presents an opportunity for the maritime sector to enhance safety, operational efficiency, and environmental responsibility.