Design and Performance of Spiral Chute Installations in India and Abroad

In coal mining, the main purpose of a chute is to transport coal from a higher level to a lower level with a minimum production of dust and the smallest practicable amount of degradation. The carrying surface of spiral chute can be considered as a helix. The design of a spiral chute is most important as the correct design will give a high standard of performance when employed in the right conditions. The main parameters which govern the design and performance of a spiral chute are the helix angle and the profile of the chute track. An incorrect design will lead to frequent blockages of the chute surface and there will be considerable degradation of the mineral transported. The motion of a particle sliding down the spiral chute has been mathematically explained in this article. The increase in fines may very within the wide limits of 2 to 20 percent, depending upon the nature of the coal and the efficiency of the spiral chute design in preventing breakage. On the basis of the literature available, the authors have designed a spiral chute for a public sector undertaking to convey coal particles up to 500 mm size at the rate of 500 tonnes per hour through a height of 18 m. A few experiments conducted by the authors on an imported spiral chute have been included. A number of experiments were conducted to determine the angle of sliding friction on which depends the tangential inclination of the chute surface. The design work was completed and the details were supplied at the end of 1967