Tiago Cousseau and Peter Robinson, from the University of Newcastle, and Shaun Reid and Jayne O’Shea from TUNRA Bulk Solids, discuss the challenges of assessing conveyor belt wear and current testing techniques, as well as the best practices to optimise belt wear resistance performance.
Conveyor belts, vital in transporting bulk materials across diverse industries, undergo continuous operation that exposes their covers to various wear mechanisms, ultimately leading to degradation. The evaluation and prediction of wear resistance are pivotal for optimising belt performance, reducing maintenance costs, and enhancing overall operational efficiency.
Tailoring test methods to belt applications
The prevailing notion of a “one-size-fits-all” solution for evaluating belt wear resistance is flawed. Wear is not an intrinsic property but a response within a tribosystem and specific operating conditions. Hence, different wear tests yield varying material performance rankings, emphasising the need for careful consideration of operating conditions and wear mechanisms in the field when selecting test methods.
Belt conveyor wear is a result of a complex combination of mechanisms influenced by the installation’s nature. For instance, overland belts with well-designed transfer chutes may experience wear due to abrasive interactions caused by belt flexure. In contrast, short plant belts may be more affected by loading conditions and ancillary equipment setup.
Diverse testing protocols at TUNRA Bulk Solids
TUNRA Bulk Solids employs a range of standard test methods like ASTM G65 and AS 1332 / DIN 53516 (Figure 1), alongside specialised tests such as the Circular Wear Tester (CWT), Impact Wear Tester (IWT), and Cut and Gouge Test (Figure 2). These tests simulate wear mechanisms under conditions representative of industrial bulk materials handling processes, as detailed in [1].
Surface analysis, as demonstrated by Lins [2] for a heavy-loaded overland conveyor belt used for iron ore transportation and by Molnar [3] for a low-load conveyor belt transporting coal, reveals four main wear mechanisms observed through visual inspection, optical microscopy, scanning electron microscopy, and/or topographical analysis [4].
These mechanisms are summarised below and depicted in Figure 3 [2,3]:
- Macro indentation (cut and gouge),
- Micro-cutting (highlighted in yellow),
- Small indentation/pits due to rolling contact fatigue (highlighted in red), and
- Schallamach waves and cracks.
Table 1 provides a detailed comparison of the usual and prominent wear mechanisms and wear rates of conveyor belts evaluated using standard tests, specialised tests, and those observed in the field. The distinctions in wear patterns based on test type and operating conditions are further discussed in the subsequent text.
These tests, operating under different conditions, result in varied belt wear resistance rankings when comparing different belts. This variability is exemplified in Figures 4 and 5, which illustrate the wear values of four distinct belt covers (A, B, C, and D) subjected to the impact (IWT) and circular (CWT) wear tests.
Figure 4 depicts wear values as a function of the impingement angle from the Impact Wear Tester (IWT). Notably, sample B exhibits the best performance for most impingement angles, while sample D shows the least favourable performance. Samples A and C fall in between, with the differences diminishing as the impingement angle increases, reaching a point (around 30-35°) where their statistical differences become insignificant.
Figure 5 illustrates wear values as a function of test duration for the Circular Wear Tester (CWT). The ranking of belts differs from the results obtained from the IWT. Here, sample B again demonstrates the best performance; however, the highest wear is observed for sample C, while samples A and D exhibit intermediate wear.
These distinctions in wear patterns based on the type of test and its operating conditions underscore the need for a nuanced approach to wear testing.
Guiding material selection through comprehensive evaluation
TUNRA Bulk Solids utilises an array of technologies to evaluate the wear rate and mechanisms of in-service conveyor belts, including Scanning Electron Microscopy (SEM) and 3D profilometers. Based on the findings and the definition of the dominant wear mode, a recommendation is made for one or more wear tests aiming to replicate the behaviour.
Data from advanced test methods play a pivotal role in predicting conveyor belt cover wear resistance. By correlating test results with real-world wear patterns and operational conditions, researchers offer valuable recommendations for improving belt performance, reducing downtime, and minimising maintenance costs.
Application-based test selection
Experience has shown that for long, heavily loaded conveyor belts with mild wear due to relative motion between the conveyor belt and feed material, tests like ASTM G65 might be suitable. In cases where abrasive particles are partially constrained on the surface, or evidence of microploughing and microcutting exists, AS 1332 is applicable. Small to medium-length conveyor belts experiencing wear under transfer chutes benefit from the impact and circular wear tests. Installations prone to cutting or gouging may utilise cut and gouge tests to identify suitable cover compounds. However, as mentioned before, an initial wear evaluation of a field-worn belt (if available) is the best practice for selecting proper wear tests.
Conclusion
In conclusion, advanced test methods are indispensable tools for enhancing the reliability and longevity of conveyor systems across diverse industrial settings. Utilising specialised test facilities, conducting comprehensive wear evaluations, and analysing wear mechanisms under field and simulated conditions provide invaluable insights to industries seeking to optimise conveyor performance and manufacturers to improve their products. In addition to standardised tests, considering specific operating conditions and wear mechanisms is crucial for making informed decisions to prolong equipment service life and enhance overall efficiency.
References
[1] S Reid et al. “Test Methods to Predict the Durability of Conveyor Belt Top Covers”. In: BELTCON21 – IMHC International Materials Handling Conference. IMHC, 2023.
[2] B. Nins et al., “Abrasiveness of iron ores: Analysis of service-worn conveyor belts and laboratory Dry Sand/Rubber Wheel tests,” Wear, vol. 506, p. 204439, 2022.
[3] W. Molnar, M. Varga, P. Braun, K. Adam, and E. Badisch, “Correlation of rubber based conveyor belt properties and abrasive wear rates under 2-and 3-body conditions,” Wear, vol. 320, pp. 1-6, 2014.
[4] J. Gates, “Two-body and three-body abrasion: a critical discussion,” Wear, vol. 214, no. 1, pp. 139-146, 1998.