A wheel loader is an extremely mobile machine fitted with tires whose job is scooping up loose materials by virtue of a continuous drive-in loading process. On the other hand, a hydraulic face shovel is a heavy machine that uses hydraulic mechanisms in digging upward from the pit floor to the face. Narrow pit bench is a term referring to a very restricted mining environment where there is little room for manoeuvring large machinery.
The first important performance characteristic here is cycle time that involves loading, swinging/reversing, dumping, and backtracking processes. The cycle time of a wheel loader in narrow pit bench conditions is significantly increased since it needs ample horizontal space for the execution of V-shaped movements. However, the hydraulic face shovel does not require much space due to its stationary nature, thus, shorter cycle time.
The other important evaluation criteria include breakout force which refers to the highest prying force produced by the bucket edge. Hydraulic face shovels have better breakout force because the geometry of the structure and cylinders used are perfect for breaking through unfragmented rock. On the other hand, wheel loaders depend largely on traction and forward motion to push the pile. Narrow benches do not allow the loaders to build up enough speed, making shovels much more productive.
Bucket fill factor measures the percentage of material load to the capacity of the bucket. Engineers aim for an accurate fill factor range between 90 percent and 110 percent (Wu et al., 2024). Hydraulic face shovels attain precise fill factors in narrow places using hydraulic action. A loader cannot penetrate the muck pile due to narrow bench widths, hence low efficiency.
The machine footprint determines the placement strategy for the loading and haul trucks to operate safely. The use of a hydraulic face shovel in mining necessitates having a small footprint, allowing for the practice of drive-by loading in narrow pits. Moreover, a wheel loader will naturally have a large turning footprint. Lastly, dust from both loaders and shovels that is released into confined spaces could affect the safety of the operation (Lashgari & Kecojevic, 2015).
Cycle time, breakout force, fill factors, and footprint must be analysed when assessing the efficiency of loading operations in narrow pit benches. Even though a wheel loader would have a wider footprint across the site, it would become highly inefficient once in tight spaces. It is in this respect that a hydraulic face shovel would be a better option, due to its stationary swinging capacity and strong breakout force.
The hydraulic face shovel will be more efficient than the wheel loader due to the fact that it operates at one place, has better breakout strength, has a precise bucket fill, and takes up less space compared to the wheel loader. Because the wheel loader uses horizontal movements to load materials, it cannot work effectively in a tight space. This leads to increased cycle time and low efficiency of the wheel loader.
References
Lashgari, A., & Kecojevic, V. (2015). Comparative analysis of dust emission of digging and loading equipment in surface coal mining. International Journal of Mining, Reclamation and Environment, 30(3), 181–196. https://doi.org/10.1080/17480930.2015.1028516
Wu, J., Zhao, J., Wang, X., & Lin, B. (2024). Multidisciplinary Collaborative Design Optimization of Electric Shovel Working Devices. Machines, 12(8), 520. https://doi.org/10.3390/machines12080520
