STUDY ON PIPE WEAR BASED ON LARGE SCALE EXPERIMENT AND SCALE EFFECT FOR DEEP SEA MINING

For the production of seafloor massive sulfides, the ores are expected to be transported as a slurry up to the sea surface. The pipe wear is caused mainly by the collision of the ores against the pipe wall, thus the evaluation of pipe wear is required for the operation of the production system. The authors conducted a full-scale experiment for evaluating pipe wear due to slurry flow. As the results, the pipe wear resistance of a SUS304 stainless steel is higher than the ultra high molecular weight polyethylene. In addition, the pipe wall thickness was measured before and after the experiment to obtain the distribution of the erosion on the pipe wall. The authors confirmed that the wall thickness reduced uniformly along the circumferential direction for vertical pipe, and the erosion occurred mainly along the bottom surface of the pipe for the horizontal and inclined pipes. Also, the authors investigated the relation between the index of the rock abrasivity and erosion and proposed a correlation for the pipe wear with the index of rock abrasivity. Finally, the authors predicted the pipe wear on the condition of full-scale experiment based on the data obtained in the reduced-scale experiment conducted previously. Then the authors compared the predicted pipe wear with that measured in the full-scale experiment.