The best of two worlds- A new concept in primary grinding wear protection

Abstract

The wear resistant mechanics of rubber and steel materials are completely different. The strength of rubber is to yield from impact forces, to become deformed when the forces are applied and then resume its shape thus avoiding any rubber material being torn off. If the impact forces are too powerful or the speed of the material hitting the rubber is too high, the wear rate will be dramatic. The tensile strength and the tear resistance of rubber are determining factors as is the resistance to fatigue. i.e. the ability to resist repeated abuse is a determining factor especially in mill linings. The strength of steel is purely hardness. Theoretically the steel would not wear if it is harder than the rock. In practice it is not entirely true, as the steel surface is not homogeneous and there is also the fatigue factor. In mill lining applications rubber has proved to work in all secondary grinding stages. In primary applications, steel linings are predominant but rubber linings have made in-roads in the last ten years. The choice of mill lining is not entirely based on wear rate. Total liner economy including downtime and maintenance should be the determining factor, but in most cases straight wear cost per ton ground materials is the key. The ratio cost per volume is in favour of rubber 1:7 to 2. Thus a higher wear rate on rubber can be accepted but the geometry of the lining is limited by the production demand of the mill. In secondary applications it is possible to use relatively thin linings and still get an acceptable wear life. In primary applications with severe grinding forces the wear rate of a rubber lining becomes a problem. Even very thick rubber linings do not achieve a reasonable wear life. The wear cost per ton basis is comparable between the two materials but the short period of time between maintenance stops makes the rubber lining uneconomical. The steel-capped lining combines the best of rubber and steel. Steel contributes with its superior wear properties in primary applications and rubber, with its lighter weight, easier, safer and faster replacement.