Experimental Analysis of a Ship Stabilization Hydraulic System

This paper discusses the results obtained by a series of tests carried out on an hydraulic actuator for a ship roll stabilizing system, suitable to be fitted on medium size pleasure crafts. These systems are constituted by 2 or 4 fins fitted on hull sides, in a proper position; the hydrodynamic forces, generated by interacting with the water flow due to ship speed, can be controlled to obtain a momentum that counteract the wave action. So reducing the effects of roll motion on people onboard and on ship structures. A full scale fin hydraulic actuator has been installed in our hydraulic test bench where an hydraulic power pack and some hydraulic valves group allow to performs various tests. Reproducing the dynamic behaviour of the fin actuator system it is possible to evaluate the influence of some hydraulic component (i.e. a proportional valve) on the system performance and the feasibility of the adoption of less expensive components. Moreover an hydraulic accumulator has been added to the plant in order to improve the fin actuation speed and to reduce the pressure spikes in order to reduce hydraulic noise. In fact noise reduction represents a very important aspect onboard pleasure boats, where every effort is made to assure a high comfort level to passengers; in particular, noise is important when the boat is anchored and the fins work; in that condition the propulsion engines are stopped, the gensets are generally well insulated, and the hydrodynamic noise is absent because the speed is zero, so the stabilizing plant is one of the main noise source onboard, with the air conditioning plant of course.