Tangential rotary picks: Wear modeling and reusability evaluation

The evaluation of reusability of conventional one-piece picks in manufacturing recyclable modular tools necessitated modeling the pick head wear. This article proposes a space–time model of the pick wear dynamics, representing the pick head in the initial condition and at the key stages of deformation depending on geological conditions of the tool operation. The model images the wear dynamics of the nose bit and steel body of picks. It allows predicting a wear stage (half-wear, pre-wear, normal wear and over-wear) of the pick heads, and determining the time of this stage. It becomes possible to find the limits of the tool wear by the criterion of reusability of the pick residues. The implemented wear analysis of picks of JOY 4LS-20 Longwall Shearer in operation in a Kuzbass mine shows that in coal cutting, the half-wear stage comes on the 6th–7th day of operation, at the residual length of the head of 76 mm, and the pre-wear stages comes on the 11th–12th day of operation, at the residual length of 67 mm. After operation for 15 days, the nose bit 28 mm long becomes totally worn, and the head length decreases from 90 to 62 mm, but the pick preserves a high potential for being reused in rock breaking. The wear limits are evaluated for the picks by the criterion of their reusability. The range and limits of wear on conventional picks by the criterion of strength of a modular structure are justified and tested. The results open prospects for multiple recycling of rock breaking tools of mining machines.