Structural analysis of a Tippler structure

Abstract

Tippler structures operate under arduous conditions for most of their operational lives. During routine structural inspections large fatigue cracks were discovered on some of the main structural components of a Tippler structure. These cracks were situated in a safety-critical area of the structure and therefore rendered the structure unsafe for operation. Structural failure could affect throughput enormously as the Tippler forms the first step in a coal terminal’s operational process. A high operational availability is therefore expected from these structures. The complex rotational working of the Tippler structure complicates the analytical evaluation of the structure. A further complication is the ever-changing boundary conditions while the structure rotates, together with the weight reduction of the coal in the wagons when the wagons are offloaded. Both these factors need to be taken into account when determining the stress levels in the structure while operational. This study identifies the main factors that led to the development of the structural cracks. The analysis process consisted of constructing a linear static finite element model of the Tippler structure and verifying the accuracy of the model by means of strain gauge measurements on the actual structure. From this analysis accurate stress values were obtained for the structure under operational conditions. A short literature study identified additional factors that would have an effect on the fatigue life of the structure under the conditions as experienced at a coal terminal. In the last part of the study the information obtained form the analysis and literature sources were applied to verify the suitability of the proposed changes made to the structure.