Investigation of Operating Range of Marine Growth Removing ROV under Offshore Disturbances

Marine growth on offshore underwater structures is a problem as it reduces the lifespan. The structures are cleaned annually by manually operated ROVs. Automation of these ROVs can improve the removal efficiency, and thereby reduce the cleaning campaign time and cost, as it is challenging for the operators to manually stabilize the ROVs under the harsh offshore conditions. Waves, ocean currents, the attached tether and the cleaning tool all generate external forces to the ROVs acting as substantial disturbances which can be rejected by a controller. This study examines the operating range of a standard compact ROV subject to external disturbances. To analyze the cleaning performance a normalized performance parameter is defined which weight the relative distance of the water jet with the most efficient distance. The results show that the waves has a larger effect on the cleaning performance compared to the ocean current. This paper examines the operating range of a reconfigured BlueROV2. For Hs≤ 1.4 m it is possible to clean in the entire operating range. To clean at all the considered sea states Hs≤ 3m and ocean currents of 0.1 - 0.5 ms^-1the ROV needs to be below 13 m.