Pit dewatering systems, techniques and practises have over past decades always contained elements of uncertainty.
This has been largely due to outdated technologies and equipment which was often undersized or over-sized to deal with a ‘worst case’ scenario.
Weir Minerals has invested heavily in research and development to overcome these challenges and can deliver an optimal dewatering solution delivered by in-house dewatering experts and advanced, modern technologies.
Delivering an effective dewatering solution requires an in-depth understanding of the external factors and parameters that may impact a mining operation – and these may change significantly between different mines says Tefo Moholi, Weir Minerals Africa dewatering product manager.
“It is critical to evaluate these criteria as a starting point.”
This article first appeared in Mining Review Africa Issue 6 2018
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.
It is therefore essential that 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.
“Further to this, and perhaps more importantly, consideration must be given on site to the permeability and porosity of the ground, the amount of surface water, geological features such as underground rivers, seasonal rainfall (particularly relevant to Central and West Africa), solid contents within the water, varying pH levels and associated chemical composition and water temperature,” Moholi explains.
The role of modern technologies in optimal dewatering systems
Mining operators consider it absolutely vital that their dewatering equipment is efficient and reliable, has a low cost of ownership over its lifespan and requires minimal maintenance – and Weir Minerals Africa is capable of delivering on all of these fronts.
“We design our dewatering systems with a high level of accuracy.”
Oversizing or undersizing equipment – which results in excessive energy use, unnecessary capital expenditure and excessive maintenance requirements – is also a challenge that can be left in the past.
“Thanks to accurate feasibility studies which can map out a dewatering plan over several years, or even the entire lifetime of the project, we can design our pumps to be the correct size and thereafter position them strategically to handle the maximum site requirements while factoring in unexpected changes to underground water systems and weather conditions.”
Weir Minerals Africa offers a variety of flexible technologies which allows the use of several types of pumping equipment such as self-primed diesel driven, submersibles and multistage pumps to high-wall designs for sites that have limited access due to high sided mine pits.
Development of sophisticated pontoon designs enables equipment to be floated out over water bodies for easier access.
Weir Minerals Africa is considered a centre of excellence for its pontoon designs which 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 new instrumentation, control and automation technologies which increase responsiveness to unexpected changes in operating conditions.
“Technology advancements in instrumentation and equipment controllers also allows fully remote and automated control systems to be utilised, reducing the need for personnel to be physically present at remote and sometimes inaccessible sites,” explains Harvinder Bhabra, senior product manager for pumps at Weir Minerals.
He continues adding that sophisticated programmable logic controllers (PLCs), for instance, 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.”
The company has also incorporated condition monitoring technology into its stable through the introduction of real-time sensors which provide customers with operational insight into the performance and reliability of critical equipment while enabling Weir experts to provide remote monitoring, preventative maintenance and process optimisation services – all ultimately aimed at extending equipment lifespans and avoid unplanned breakdowns.
This technology is ideally suited to the full Weir Minerals dewatering product range.
Designed in conjunction with international software and technology experts, the custom-designed sensors can be attached to any Weir Minerals Africa product.
It tracks vibration trends and uploads this data to the cloud which can be accessed 24/7 from across the globe on any internet-connected device.
This technology will prevent catastrophic failures and demonstrates the company’s evolution as a business to incorporate fourth generation digital technologies that the industrial world is quickly embracing.
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 at the same time as lowering the total cost of ownership of a particular product,” Moholi highlights.
Combining technology with the correct equipment delivers the best results Moholi adds. Weir Minerals Africa has a diverse range of dewatering products within its portfolio – which it considers a starting point when determining the best solution for a client.
“We look at fit-for-purpose solutions tailor-made for specific applications, as opposed to providing an off-the-shelf product.
“Having access to a global network of experts within the Weir Minerals Division offers benefits in this area. In some instances, a slurry pump is best suited to a dewatering application due to the high solid content in the water.
“This level of consideration on an application shows our position as not just an equipment supplier but rather a service provider.”
Ultimately, all mines are different and each site’s dewatering plan should be as individual as the operation itself.
A ‘one size fits all’ approach is inappropriate when the water characteristics and flow requirements of each site differs.
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.