This paper deals with experimental approaches for enhanced understanding of the hydraulic performance of a hybrid pick-up device developed at KRISO. The experiments were conducted in a 2-D flume tank. The hydraulic nodule lifter of the hybrid pick-up device consisting of water-jet piping and baffle plates was manufactured and tested. Flow rate of water-jets, tow speed, bottom clearance, and position and shape of baffle plates were chosen as experiment parameters. Through a series of experiments, the pick-up efficiency of the hydraulic lifter has been analyzed as function of the experiment parameters, and operation condition assuring high pick-up efficiency has been identified. In order to investigate the working principle of water-jets, the bottom pressures fluctuating due to water-jets were measured with varying conditions of water-jets flow rate, tow speed and bottom clearance. The characteristics of bottom pressure distribution were studied in correlation with the pick-up efficiency. It was recognized that there is a correlation between high pick-up efficiency and longitudinal pressure distribution.
A profitable exploitation of manganese nodules from deep-seabed of 5,000m water depth is feasible on the premise that there is a large scale nodule collector with maximum collecting capacity of 500 ton/h (Herrouin et aI., 1989). Effective collecting of manganese nodules out of sediment upper layer of deep seafloor is beginning of an economic and environmentally acceptable mining operation. A hybrid nodule pick-up device has been designed on the concept that direct mechanical disturbance of deepseabed environment should be avoided and the sediment of seafloor is kept at seabed as far as possible (Oebius, 1993, Amann, 1995, Min et a1., 1997). Hong et a1. (1997) conducted kinematic analyses of pick-up device motion for the purpose of motion control system design. Mechanical conveyor transports only the nodules inside collector by rotating finscraper.
