Belt conveyors are widely used in the mining industry, both in open-cast and underground mines. They offer advantages such as rapid transport of blasted heaps from the depths to the surface, and many others. However, their use in underground mines has a number of drawbacks. Let’s explore some of them.
Fire hazards
Underground conveyor belts, especially rubber ones, pose a significant fire risk. Fires can be ignited by mechanical failures such as frozen idlers or electrical faults. Once a fire starts, it can spread rapidly over long distances, producing toxic fumes and consuming oxygen in the confined underground space. This risk is exacerbated by the presence of combustible materials like coal dust. Therefore, underground belts must meet strict fire-resistant standards and often require fire suppression systems.
Dust explosions and air quality
Coal or mineral dust accumulation around conveyors can lead to explosions if ignited by sparks or hot components. Dust also degrades air quality, which is already a concern in underground mines, necessitating dust control and ventilation measures.
Mechanical failures and maintenance
Conveyor belts require frequent inspections and maintenance to prevent issues such as belt misalignment, tension failures, roller wear, and edge wear. Mechanical failures can cause material spillage, damage to the belt, and safety hazards for workers. Maintenance in underground conditions can be challenging due to space constraints and harsh environments.
Limited material handling flexibility
Conveyor belts have limitations on the size of material they can transport; for example, they generally cannot handle oversize fragmented rock exceeding about 300 millimeters. This contrasts with dump trucks, which can carry almost any broken rock size. This limits the conveyor’s applicability depending on the material characteristics underground.
Fixed path and inflexibility
Conveyor belts are fixed installations with limited ability to change routes or adapt to new mining layouts without significant modifications. This inflexibility can be a disadvantage in dynamic underground mining environments where layouts may change.
Gradient and distance constraints
While conveyors can operate on steeper gradients than trucks (up to about -12°), economic and operational efficiency depends on mine depth, gradient, and distance. For short distances or shallow gradients, trucks may be more economical. Conveyors are more suited for long-term, large-scale projects due to high initial investment and continuous operation benefits.
High initial investment and energy use
Conveyor systems have high upfront costs for purchase and installation. Although running costs are generally lower than trucks, energy consumption can be significant, especially over long distances or with heavy loads. This impacts operational costs underground.
Safety risks to workers
Moving parts like rollers, pulleys, and tension systems can cause injuries if workers get caught. Entrapment and pinch points are serious hazards requiring strict safety protocols and protective measures.
Material spillage and environmental exposure
Open conveyor designs may lead to material spillage and exposure to environmental contaminants, causing material loss and additional cleanup efforts. Covering conveyors underground can be complex and costly.
In summary, while underground conveyor belts offer continuous, efficient material transport with lower labor and emissions compared to trucks, their limitations include fire and dust explosion risks, mechanical maintenance challenges, inflexibility, material size constraints, high initial costs, and safety hazards that require rigorous management.
Image credits: Continental (Available on: https://www.continental.com/en/press/press-releases/24/7-smart-service-for-the-toughest-mining-conditions/)
