Investing in the future of dewatering
The vast majority of mining involves working below the water table, which means a comprehensive and flexible dewatering plan is essential – particularly as mine workings go deeper to reach diminishing stocks of ore. Weir Minerals looks at how technology enables equipment providers to remove water from a mine and put it to good use afterwards.
Mines cannot operate without a robust and flexible dewatering strategy. As no two mines are the same, each site’s dewatering requirements will vary, with environmental and geological considerations as well as local climatic variations likely to present unique challenges.
Variations in weather conditions can significantly affect open-pit mining in particular, and even mines operating above the water table can be subject to significant influxes of water caused by environmental changes such as heavy rainfall or, in colder climates, melting snow in the springtime. It is essential, therefore, that the dewatering systems in place have the capacity to handle the maximum potential volume of water inflow to avoid downtime and prevent any risks to safe operation.
A variety of factors dictate the type of dewatering system required for a specific mine. The permeability and porosity of the ground, the amount of surface water, geological features such as underground rivers and seasonal rainfall must all be assessed and factored into a detailed dewatering system before work can begin.
At the forefront of every operator’s requirements from their dewatering equipment are efficiency and reliability, lifetime ownership cost and ease of maintenance.
How does technology help?
There was a higher level of uncertainty in the design of dewatering systems in the past due to the available technology at the time, and equipment was often oversized to deal with a worst-case scenario. Modern geological surveying methods have allowed dewatering systems to be designed with a much higher level of accuracy, and the advances in sophisticated instrumentation and control equipment mean that systems can be optimised with much better control. The obvious pitfalls of over or undersized equipment include excessive energy use, high cost of investment and maintenance and risk to equipment and personnel as well as lost production in the case of insufficient capacity.
Today, accurate feasibility studies can map out a dewatering plan over several years, or even the entire lifetime of a project, with pumps located strategically and designed to handle the maximum site requirements, including factoring in unexpected changes to underground water systems and weather conditions.
Flexible technologies allow the use of several types of pumping equipment such as from self-primed diesel-driven, submersibles and multistage pumps to high-wall designs for sites that have limited access due to high-sided mine pits. The development of sophisticated pontoon designs also allows equipment to be floated out over water bodies for easier access. The designs are either fixed to banks with access walkways or standalone installations. All designs are rigorously tested and include optimum safety features to help prevent risk to operators. The pontoons can be constructed from a variety of materials from heavy-duty steel to low-density polyethylene with steel frames, for lighter applications. Each pontoon is designed with a fully tested anchoring system and can also be customised for extreme weather conditions.
Flexibility in the latest dewatering systems is achievable through the latest instrumentation, control and automation (ICA) technologies, increasing responsiveness to unexpected changes in operating conditions. Technology advancements in instrumentation and equipment controllers allow fully remote and automated control systems to be utilised, reducing the need for personnel to be physically present at remote and sometimes inaccessible sites.
Sophisticated control systems can control the pump operating speed to adapt to changing conditions in the water levels, start up or shut down of equipment in response to other external factors. In addition, mechatronics engineering systems are developing rapidly, enabling monitoring and maintenance to be carried out remotely. Monitoring of equipment and prediction of performance is also being developed to allow better planning for maintenance.
These smart products can be connected via cloud services to provide a live status for any piece of equipment, which safely increases productivity and efficiency.
Fast-moving data acquisition, storage and analysis all play a vital part in the continual process of improving the operating performance of equipment, and ultimately can help restrict environmental impact at the same time as lowering the total cost of ownership of a particular product.
Weir Minerals invests heavily in a Research and Development programme through its internal resource and is actively involved with a network of academic research partners in universities around the world, working on technologies.
Water, water everywhere
The composition of the water being moved has a significant effect on the equipment and materials used. The pH range, temperature, corrosive and abrasive content as well as specific gravity of any present solids, all affect what equipment provides the optimum solution to transport the water effectively.
The presence of solids in the water, the specific gravity, size distribution and content percentage will determine the type of pumps required. It may be that slurry pumps are needed to handle a higher content of solids, as traditional dewatering equipment is designed for lower solids contents.
Equally, the pipework and valves are also subject to corrosion and abrasion from the products handled and must be designed accordingly. Burst pipes create a major safety hazard as well as interruption to production.
Waste not…
Dewatering processes also support the ever-increasing emphasis on turning waste into energy as global resources are depleted. Technology is allowing manufacturers to produce equipment that not only dewaters mines to allow safe extraction of ore but which can then be recycled and re-used either within the mining process or, if necessary, by the wider community after necessary processing for commercial or domestic use. This helps to reduce the negative impact on the environment.
The quality of surface and groundwater from a mine is monitored and treatment processes are utilised to ensure it meets the correct standards before being discharged either for disposal to waterways or for use by the wider community.
An individual solution
All mines are different, and each site’s dewatering plan will be as individual as the operation itself. A ‘one size fits all’ approach is inappropriate when the water flow requirements of each site will be different, not to mention other variations such as operating depths and existing piping systems. Technology is helping both in the planning stage, to draw up comprehensive and reliable dewatering plans, and to optimise the use of the equipment during the process itself.
