Used in ore storage and homogenization yards, better known as yard machines, they are large and important assets for mining companies. This equipment is responsible for handling materials in pile construction or recovery operations. This article discusses the work carried out by the company on the stability analysis of an ore reclaimer.

The Kot Blog has an expository text on the structural analysis of one of these machines and you can check it out here.

Introduction

Kot took on the responsibility of analyzing a bucket wheel reclaimer. The equipment has been in operation since 2006 and handles iron ore with great capacity. During operation, the machine is able to travel parallel to the piles of material and also rotate around its own axis. The equipment has a boom capable of tilting vertically parallel to the height of the pile. 

The computational analyses were carried out using FEM software. The three-dimensional computer model of the reclaimer can be seen in Figure 1.

Figure 1: 3D finite element model of the reclaimer. [1]

To begin the study, the first step was to model the reclaimer using finite elements. The machine's structures made up of structural profiles were modeled in bar elements and statically checked according to the recommendations set out in the standard. The other structures made up of structural plates were modeled in shell elements and evaluated according to international standards. Some of the loads considered in the analysis are listed below.

• Weight of the metal structure and installed equipment;
• Loading material onto the belt conveyor;
• Dynamic effects of material transport on the belt;
• Overloading of stairs, walkways, platforms and roofs;
• Loads due to operating wind;
• Chute blockage.

After modeling, applying loads and boundary conditions, the machine was evaluated from a structural point of view. Further details of this analysis can be found in the Succes story below.

Case Study: Structural Analysis of an Ore Recovery Machine

Stability analysis

Global stability analysis consists of assessing the possibility of a machine tipping over. To do this, the stability safety index, defined by standard, is calculated for all combinations of loads and operating situations relevant to the study.

Two different stability studies were carried out for the reclaimer, one considering only the rotating mass and the other with the complete machine. The first analysis checked whether there was a risk of the anti-tip device being required, while the second analyzed the risk of the machine tipping over completely.

Figure 2 shows the stability polygon evaluated in the stability analysis of the upper part of the machine. Each edge of the polygon is considered a possible tipping axis that would trigger the anti-tip device.

Figure 2: Stability polygon considered in the analysis of the rotating structure. [1]

Figure 3 illustrates the stability polygon evaluated in the stability analysis of the complete machine. It should be noted that each edge is also considered a possible overturning axis of the reclaimer.

Figure 3: Stability polygon considered in the analysis of the complete reclaimer. [1]

In order to validate the efforts and the model created, Kot carried out the instrumentation of strain gauges at points in the equipment's translation system. After installing the sensors, the operation commanded by the company's team was carried out, rotating the equipment in order to vary the demands on each leg of the portal to collect the deformation variations via extensometry.

The results obtained in both stability analyses were positive and the machine was approved from this point of view. It should be noted that during the analysis it was found that the anti-tip system would not be activated, and in both analyses all the demand indices found were lower than the safety indices. 

In addition, the data obtained from the field instrumentation proved crucial for validating the study, as it was possible to determine the equipment's center of gravity with the aid of the finite element model.

Conclusion

Stability analysis of yard machinery is an extremely important study for companies. Equipment tipping over like this can cause catastrophic accidents, resulting in fatalities, production stoppages and inestimable financial losses.

Kot has a great interest and a wide range of knowledge to study various engineering contexts. Contact our team for more information!

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References:

[1] Kot Engenharia Collection.