A mining stockpile is a pile or storage location for materials/product which has been extracted through the mining process. Stockpiles exist across many industries not just mining and these include refineries, construction zones, manufacturing facilities and ports.
Bulk material handling at mines
Stockpiles form part of bulk material handling at mining operations. Four key objectives of storing, safety, grading and measurement impact stockpile management.
Product handling
Mining equipment brings material to the surface, crushes and screens the loads, then hauls and stockpiles into multiple stacks. A simple stockpile forms when dump trucks or bulldozers deposit bulk quantities of ore or coal into a pile. More controlled methods use stackers that create piles along the length of a conveyor with each pile reclaimed separately using specialised equipment. Managers can then inspect these individual stacks and analyse them according to pre-defined requirements to generate an accurate profile of the materials.
Coal mines designate coal preparation areas where coal is washed, impurities like soil and rock removed and then graded. This arrangement also helps to remove contamination of material like bits of the machine tools used in the extraction process. Other components for removal include ash and sulphur. The intention is to ‘purify’ the coal as far as possible to generate bulk loads, which will ultimately cost less to transport and have a higher market value per ton. Consumers of coal products depend upon uniform composition for efficiency in their furnaces.
Human intervention
Physical labour processes also have their shortcomings: these include the time-consuming efforts when loading a consignment for transport, and grade control compliance when workers supervise loading each stack into particular vehicles or rail wagons. Automated processes also require human oversight, so responsible mining companies ensure that all safety procedures are in place.
Optimising stockpile procedures
The quality control chain of activities in stockpile management focuses on optimising product quality and operational efficiencies. Mining material management is a key to mine site performance and profitability, and this is where good management of a stockpile comes in. Producers are interested in maximising their assets and are inspecting how well-designed and operated stockpiles can improve key metrics, such as plant utilisation versus plant availability ratios. Part of this process is to refine their stockpile strategy, take advantage of equipment and control-system advances to refresh stockyard infrastructure and, through improved material flow and quality control, reinforce their capability to maintain a good market share for their products.
High on the list of upgrade objectives are the automation of all or part of stockpile operations, replacement of old stacker-reclaimer equipment with newer models, and quicker, more accurate stockpile accounting. Part of this process is measuring:
- how much extract has been added to a stockpile (i.e. stockpile balance);
- the location and value of material; and
- how efficiently material moves from the pit to the preparation plant.
This has traditionally been done manually or else using standard software programs. But newer technology, such as and others, helps measure (and therefore manage) other operational challenges such as:
- poor plant utilisation and product quality;
- lack of optimisation with checking compliance to particular processes; and
- poor resource modelling.
Heavy equipment used in stockpile clearing
Front-end or wheel loaders and bulldozers are the most used pieces of equipment for either pushing product into feeders or reclaiming coal from the stockpile. There is a low up-front capital cost (amortising plant and equipment overheads over time), but high operating expenses, measured in the relevant currency per ton handled.
Photo by Curioso Photography from Pexels
Moving boom stackers that straddle a feed conveyor are commonly used to create coal stockpiles. They normally travel on a rail between piles in the stockyard. A stacker can usually move horizontally along the rail and vertically by raising and lowering its boom.
Choosing the right equipment for the demanding tasks carried out at coal mines is worth a consultation with specialists like Unitrans Africa who can advise on suitable plant machinery.
Legislation affecting mine dumps and stockpiles
Regulations within the last five years have changed the way mining operators plan and manage stockpiles. Environmental Acts require that stockpiling is conducted appropriately, especially when it comes to the handling, storage, treatment, transfer, transportation and receipt or disposal of waste or other matter. As there are human health risks involved in mining, regulations also encourage the circulation of materials to waste management processes wherever possible. Fortunately, it has become increasingly apparent that this environmental responsibility often links positively with economic efficiency.
Registered civil or mining engineers must now design stockpiles, which must comply with landfill requirements. In South Africa, for example, stockpiles must comply with the National Norms and Standards for the Assessment of Waste for Landfill Disposal, 2013; and National Norms and Standards for Disposal of Waste to Landfill, 2013 found here.
Because of the various pieces of legislation, the requirements for establishing and managing stockpiles and residue deposits are not only more stringent but also more expensive. However, given the enormous costs of correcting environmental damage, expenditure on these preventive measures is likely to be an acceptable investment.
Technology to manage stockpiles at Mines
Effective stockpile management depends on accurate, timely readings on the volume and content of piles. These surveys need to be accurate and completed quickly. However, until fairly recently operators could not have both criteria and ended up either having to spend a lot or else invest in many resources.
To use all assets effectively, mine producers are taking advantage of new technology tools and equipment. These provide control systems that evaluate the infrastructure of stockyards to improve material flow and quality control.
When considering an upgrade to make better use of digital opportunities, high on the list of priorities are:
- automation of all or part of stockpile operations;
- replacement of old stacker-reclaimer equipment with newer models; and
- quicker, more accurate stockpile accounting.
Comprehensive mine scheduling software solutions from major vendors include either integrated or optional stockpile modules. More specialised software packages and services focus on material tracking and blending, whilst decision-support software helps to solve stockpile-related issues.
Drone Technology for Mine surveys
Mining profit lies in volume so it’s crucial to have the most accurate measurement of stockpile size. Previously, these processes were estimates, performed manually using ground surveys and GPS technology. Not only were these time-consuming but also expensive, especially if one considers the cost of keeping a mine running for longer than necessary.
Traditionally a survey crew would walk the site and climb stockpiles to measure them. But this has risks, delays data collection and analysis, and may even require operations to shut down while teams are taking measurements. Technology used in Unmanned Aerial Vehicles, or UAVs/drones, can:
- reduce manual labour;
- have safety benefits; and
- quickly provide operators with accurate stockpile evaluations at a lower cost.
The various pieces of equipment include:
- SLR cameras;
- Sensors;
- LiDAR (measuring distances with laser light); and
- satellite imagery.
These all link to computer software and smartphone apps. Hand drawings and manual assessments can now be a thing of the past.
More and more miners are turning to drone technology to streamline daily operations and assist with one of their most time-consuming tasks, stockpile measurement.
Mining stockpile management is one of the most mundane links in the mining chain, but is critical to operational efficiencies and ultimately profit. Unitrans Africa offers professional and sound advice about using the right equipment for the task at hand. They have a variety of services for mining operations, including input on streamlining production and saving costs. The company is proud of its logistical innovation across all areas of mine management. Material-handling solutions include technology, resources, and fleet recommendations to ensure mining operators can meet the size and detail requirements of their projects.
As a leader in mining solutions in Africa, with a strong footprint in countries such as Madagascar and Namibia, Unitrans Africa is the right call to make. Find out more about stockpile control solutions by getting in touch with one of their professional consultants.
Header Photo by Tom Fisk from Pexels.
