The future of mining is electric: it's cleaner, cheaper and more efficient. In recent years, more mines are utilising electric excavators and vehicles, particularly in underground mines where ventilation is paramount and exposure to diesel engine exhaust is a major concern. These changes have also been driven by improved battery technology, which allows equipment to run for longer.
These benefits are, broadly speaking, acknowledged in the mining industry. But electric vehicles - excavators, dump truck and compactors, for instance - are low hanging fruit: the technology exists and is proven and, once the infrastructure is in place to support it, operating costs are dramatically reduced.
While these benefits are comparable for a lot of mining equipment, the challenges are not; indeed, when it comes to operating equipment that requires much more horsepower, like many of Weir Minerals' range of dewatering pumps, there are some additional challenges that are not easily overcome.
Challenges
Operators who've always used diesel-powered dewatering pumps and are confident in their capabilities are often hesitant to embrace electrification. In many cases, electric dewatering pumps weren't even an option when they started out in the mining industry. But, as stakeholders and shareholders increasingly want to decarbonise and as the technology continues to improve, there is a growing willingness among operators to learn more about the benefits associated with electric dewatering pumps.
It's worth addressing some of the commonly expressed concerns in the industry.
Operators can move their diesel-powered dewatering pumps around the site because the power source is obviously enclosed within the pump. Even if the pump is mostly stationary - performing the same duty day-in-day-out - the possibility of it being mobile provides operators with flexibility.
Operators often express concern about the challenges associated with the variable speed control of electric motors. They understandably draw attention to the ease with which they're able to change the speed of diesel dewatering pumps, by simply adjusting the throttle or engine speed settings.
Addressing these challenges
Electric dewatering pumping systems require additional infrastructure that is easily adaptable to get power to the required locations, so it's more difficult to accommodate last-minute changes of equipment location. Evidently, operating electric dewatering pumps requires careful planning that takes this into account. However, as the electrification of mine sites becomes more common - starting with, say, electric vehicles - this infrastructure will become more prevalent and readily available.
Variable speed control on electric-powered units is also more complex because the motor runs at a fixed speed. In a synchronous electric motor, the rotor uses a permanent magnet or electromagnet to rotate at the calculated speed.
A permanent magnet motor has a number of poles, which will determine the fixed synchronous operating speed of the motor. The drive units for Weir Minerals' dewatering pumping systems are commonly available in two, four and six poles, while the
fixed rotating speed for each of these pole configurations will also be effected by the motor frequency. Depending on the region, this will be either 60Hz or 50Hz.
The speed of the electric motor can also be changed using a variable speed drive (VSD), sometimes known as a variable frequency drive (VFD), which adjusts the input frequency. The duty point - the intersection of the flow rate and discharge head - for dewatering pumping systems is generally not achieved by units operating fixed speed motors. Therefore, the pumps' rpm needs to be adjusted with a VSD in order to optimise the system and provide maximum energy savings.
Benefits
As governments, regulators, stakeholders and shareholders push the mining industry to decarbonise, phasing out fossil fuel driven equipment will become increasingly common. In terms of energy consumption and carbon emissions, the benefits of electric units are widely understood and acknowledge. This energy efficiency also dramatically reduces operating costs. When it comes to Weir Minerals' range of dewatering pumps, electric-powered units - that's to say, when the cost of diesel fuel is compared to the cost of electricity - are approximately five times less expensive to run (depending on fluctuations and regional discrepancies in price, of course).
The maintenance costs for equivalent sized electric motors are also considerably lower. Diesel engines are mechanical, so the wear can be significant, while the maintenance requirements can be onerous. They require on-going preventative maintenance, which is typically scheduled for every 250 operating hours. This includes things like changing the fuel, oil and air filters.
With an electric motor, the operator plugs it in and, aside from occasionally lubricating some bearings, it just keeps spinning. Maintenance costs are, therefore, a fraction of the cost.
For example, the operating life of an electric motor with an L10 bearing life is around 40,000 hours. A diesel engine, on the other hand, based on a 250 hour engine service interval, requires 160 services to be completed. If an average time to complete the diesel engine service is four hours, this equates to 26 days of lost pumping time. Furthermore, operators also have to dispose of the oil and oil and fuel filters, which is an additional expense.
Safety Concerns
Another significant advantage of operating an electric-powered dewatering system is the reduction in noise pollution. An open to air diesel engine operating at 1800rpm will produce approximately 80+ decibels at 5m (15ft). Without hearing protection, this sound level can cause serious auditory injury over a single working day. This is a serious concern to mining operators; while these long term injuries can only be prevented by implementing safety procedures and supplying Personal Protective Equipment (PPE), it's more effective to eliminate the hazard altogether.
Comparatively, a four pole 60Hz electric motor with a 1800rpm operating speed produces approximately 15 decibels at 5m (15ft). This provides a significantly safer working environment and also allows personnel working near or around the operating equipment to communicate easily.
Digitalisation
As the mining industry embraces digitalisation and all the possibilities this entails, electric units integrate much more easily with remote monitoring technology. In diesel-powered units, the data that reports on the health of the equipment is collected by sensors. In other words, operators use electrical technology to monitor mechanical equipment. It's not just simpler to collect this data when the motor is electric, it's also more accurate and less likely to fail.
