Case study on wear resistance treatment for spiral agitators in tower mills

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The tower mill is a new type of efficient and energy-saving wet grinding equipment. It features a spiral stirrer inside the cylinder, along with grinding media filled within it. As the spiral stirrer rotates, the grinding media exert continuous forces such as compression, shearing, and stripping on the material. The large contact area between the grinding media and the material results in high grinding efficiency, thereby significantly reducing the power consumption per unit of product produced by the tower mill. The energy-saving effect exceeds 30%, **reducing production costs. Tower mills are mainly used in industries such as metallurgy, metal mining, building materials, and environmental protection. As an efficient crushing device, a tower mill mainly consists of four parts: the machine body, the stirring screw, the driving mechanism, and the grinding media inside the tower. A spiral mixer generally consists of a spiral body, an anti-wear lining on the spiral body, and spiral blades at the bottom. Due to the imbalance in forces between the grinding media and the material, a velocity gradient is created within the fluid layer, which in turn generates local shear forces, compressive forces, and impact forces between the particles themselves as well as between the particles and the steel balls, thereby achieving a fine grinding effect. Prolonged impact forces can cause significant damage to the mixing screw. To extend its service life and reduce wear on the equipment, we can apply a polyurethane coating to the blades and the screw body of the mixer for wear resistance. Spraying application of polyurethane elastomers: 1. Surface pretreatment: The substrate surface is treated to give it a metallic white appearance using steel sand spraying, thereby creating anchor patterns with a depth of over 50 μm on the surface; this helps to achieve the best bonding results. 2. Application of adhesive: After surface treatment is completed, the second step is carried out, which is applying the adhesive. The adhesive can be applied by spraying or brushing. The adhesive must be applied in 2 coats; after the first coat has been applied, it must dry completely before the second coat can be applied. Approximately 30–50 minutes after applying the second coat of adhesive at room temperature, the polyurethane material can be sprayed on. When applying the adhesive with a brush, it is necessary to ensure even application without any missed areas. 3. Spraying: The thickness of the coating applied using polyurethane repair materials is determined based on factors such as operating conditions and design requirements. It is essential that the spray gun moves at a constant speed to ensure that the thickness is uniform and the surface remains smooth.