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Mines operating above the water table can experience significant influxes of water caused by environmental changes, eg heavy rainfall or thawing snow.
Mines operating above the water table can experience significant influxes of water caused by environmental changes, eg heavy rainfall or thawing snow.

Investing in the future of dewatering

As the vast majority of mining involves working below the water table, a comprehensive, flexible dewatering plan is essential. Harvinder Bhabra outlines how the latest pump technology enables producers to not only remove water from a mine but also 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 and local climatic variations likely to present unique challenges.

Variations in weather conditions can have a significant effect on 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 are efficiency and reliability, lifetime ownership cost and ease of maintenance.

How technology helps

There was a higher level of uncertainty in the design of dewatering systems in the past, due to the available technology, 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 advances in sophisticated instrumentation and control equipment means systems can be optimised with much better control.

The obvious pitfalls of oversized or undersized equipment include excessive energy use, high cost of investment and maintenance, risk to equipment and personnel, and 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 the project, with pumps located strategically and designed to handle the maximum site requirements, factoring in unexpected changes to underground water systems and weather conditions.

Flexible technologies allow the use of several types of pumping equipment, from self-primed, diesel-driven submersibles and multi-stage pumps to high wall designs for sites that have limited access due to high sided mine pits.

The development of sophisticated pontoon designs also enables 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. 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 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 programmable logic controllers (PLCs), for instance, can control the pump operating speed to adapt to changing conditions in the water levels and start-up or shutdown 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 latest “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 while lowering the total cost of ownership of a particular product.

Weir Minerals invests heavily in a research and development program through its internal resources and is actively involved with a network of academic research partners in universities around the world, working on technologies.

The development of sophisticated pontoon pumps enables equipment to be floated over water bodies for easier access.
The development of sophisticated pontoon pumps enables equipment to be floated over water bodies for easier access.

Waste not …

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.

There is an increasing emphasis on turning waste into energy as global resources are depleted, and the dewatering process is no different. 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 reused 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 utilised to ensure it meets the correct standards before being discharged either for disposal to waterways or for use by the wider community.

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 equipment during the process.

Weir Minerals offers a full range of dewatering products, from vertical pumps to floating pontoons and barges, from long established brands such as Multiflo, Warman and GEHO.











ABOUT THE AUTHOR
Harvinder Bhabra

Harvinder Bhabra is a senior product manager for pumps at Weir Minerals.









Wednesday, 22 May, 2019 5:03am
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