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.

The new method for assessing rock abrasivity in terms of wear of conical picks

During the exploitation of mineral raw materials, a cutting tool is an element that is directly in contact with the unmined stone being cut. The most commonly used cutting tools include conical picks. The increasing pressure to reduce mining costs causes an increasing demand for affordable and reliable ways to increase the reliability of mining machines. Abrasive wear is the most common process affecting the wear of shearer picks, hence a good and simple laboratory method for assessing rocks abrasivity is needed. The new method was developed in the aspect of selection of conical picks with appropriate protection of the pick working part, increasing its durability. The method involves the assessment of mass abrasive wear of a standard steel pin and rock sample, and the determination of the abrasivity index Wz of the tested rock, as the ratio of the mass loss of the steel pin to the mass loss of the rock sample. The article presents the procedure of conducting tests, construction of a laboratory test stand and the use of the developed method to assess the abrasivity of gangue rocks occurring in the currently cut tunnel excavations of Polish hard coal mines.