Professional Articles

Wear & Abrasion

Wear in Bulk Materials Handling

After a survey of contact and fracture mechanical correlations to be considered, models for the description of abrasive wear and flow erosion caused by bulk solids will be discussed. Here a differentiation will be made between ductile and brittle wear body materials. These models can only be applied to limited strain situations. They do, however, help to show which influencing factors are relevant to which extent for the wear behaviour and provide concrete information for the solution of actual wear problems, e.g. by the selection of suitable materials. Further, they allow for a scale-up as well as a consistent evaluation and interpretation of the results of wear measurements on a technical and laboratory scale. A survey of the requirements necessary for wear tests concludes this paper.

1. Introduction
The handling of bulk solids is generally associated with significant wear to the plant equipment and components used. This is caused by either permanent or temporary contacts between the bulk solid and a wear body, e.g. component walls, tools, etc., with simultaneous relative movement or impact. The strain produced this way can lead to separation of wear particles from the wear body as well as to the fracture of bulk solid particles, i.e. wear and grain destruction are competing processes during all steps of manufacturing and processing a bulk solid.
Besides the method of bulk solid handling, e.g. mechanic / pneumatic transport, mixing, storage, crushing, and the selected operating conditions, the characteristics of the bulk solids such as particle size, shape and hardness, mainly determine the extent of the wear to be expected. From this, however, it should not be concluded that for a wear analysis the evaluation of the bulk solid as such is sufficient. Rather, an analysis of the total wear system is necessary in any case [1,2]. Wear is no characteristic of the material but of the system. Resulting wear costs frequently arise not so much from the expenditure involved in replacing the worn part itself but more from the consequential costs resulting from the „unforeseen“ damages, such as a breakdown in the production process. The following strategies can be applied to reduce direct and indirect wear costs: . . .