There are a lot of challenges when operating in sub-zero temperatures. From a water management perspective, ice presents a number of risks that need to be considered and worked through.

For instance, Weir built a mega barge system – which is essentially a floating city – about 1km from the shore of a tailings pond. To access it, a floating walkway was required, which is something Weir regularly delivers, but when the temperatures can reach –45°C (with the wind chill it feels like –65°C) humans start to experience the onset of hypothermia in less than ten minutes. As a result, Weir had to install warm-up stations every 100m. There obviously wasn’t an off-the-shelf solution for this.

This is just one example, but it highlights some of the unique challenges associated with operating in extreme weather conditions and the importance of partnering with suppliers that have a proven track record, product portfolio and expertise to deliver dewatering solutions in the most trying environments.

Updating a water reclamation system

Weir was recently approached by a customer that was having reliability issues with its water reclamation system. A submersible pump was being floated on a simple float. Because of the type of pump being used, the customer needed to keep it close to shore, which meant that it was pulling in a lot of dirt from the bottom of the pond when the level dropped. The pump also wasn’t providing the performance (flow) the customer required because of to the high system head conditions.

Initially, the customer considered simply replacing the existing pump with one that could handle solids, but this would mean that dirty water would still be pumped into the process. In other words, it would have been a band aid solution that did nothing to address the downstream issues.

When the Weir team walked the site, they quickly identified a number of ways to improve the efficiency of the system. Firstly, by optimising the routing of the piping, the length of piping and the head requirements of the system could be reduced. The existing pipe system was all steel and, after some testing, the Weir team realised that it was corroding and, as a result, a potential point of failure, as well as increasing the frictional losses.

Weir proposed a shorter, HDPE (high density polyethylene) piping system, which had a much lower coefficient of friction and, with those savings alone, less than half the pressure was required to get the same discharge point. A lot of the valves were also replaced, further reducing friction points in the system.

Once the duty point of the pump was established, Weir provided the customer with a range of pumping options. After considering a number of submersible pump options, the customer opted for Floway® vertical turbine pumps (VTP) because it was the best pump for the duty point. It’s straightforward to operate, very efficient, and, because the discharge head and motor sit out of the water, it’s easy to inspect and maintain the seal system.

The Floway® pump was mounted to a barge that was stationed far enough offshore to ensure it didn’t pump any dirty water. The operator also wanted to be able to inspect the pump easily. As a result, because the barge is then classified as a manned floating system, it required marine architect certification.

Essentially, these barges need to be certified for the worst case scenario, like a one in 50 year storm. In order to obtain this certification, Weir analysed the historical climate data from the site location, it considered things like the wind, snow and seismic loading, then ran simulations to see what kind of waves these events would likely generate. Weir then designed a mooring and anchoring system that will hold in place in these simulated worst case scenarios.

Weir delivered a Multiflo® CC polyethylene pontoon barge that’s easy to install and scalable, allowing the customer to expand the system as its operations continue to grow.

Operating in the harshest environments

One of the major challenges with this bespoke solution was that it had to operate in an environment in which temperatures can range from –45°C to +40 °C. These extreme lows obviously create ice, which presents a number of risks to both the pontoon barge and the piping.

For instance, ice can potentially puncture the barge hull, so it’s important that the surrounding water remains ice free. Weir’s solution included a de-icing system, which is a bit of a misnomer because what it actually does is prevent ice from forming in the first place.

Weir engineered a system that utilises the geothermal effect of the water – essentially, pulling warm water from the bottom of the pond to the surface, thereby creating constant recirculation – to ensure ice doesn’t form. Provided the pond is deep enough, this solution is effective at some of the lowest temperatures ever experienced on earth – say, to around –60°C.

Weir’s solution also included self-draining pipes. If frozen columns are allowed to form in the pipes they’ll rupture or crack and need to be scrapped. Typically, heat trace systems are employed to prevent this; these systems are made up of a resistive element that heats up when electricity passes through it.

However, if there’s a power outage, which does occur, particularly at remote sites that experience extreme conditions, the system fails.

For this reason, Weir opted for a self-draining system so that, in the event of a power outage, the system drains in a matter of minutes and damage to the piping system is avoided.

Unique challenges require tailored solutions

There are common challenges across the whole mining sector, but each site has its own set of unique constraints based on variables like the climate, the location, the topography and the nature of the ore body, among others.

As a result, innovative thinking is often required to develop solutions to overcome these challenges. With a global footprint, a product portfolio that covers the entire flowsheet – from extraction to processing, dewatering and tailings management – and unrivalled engineering expertise, Weir has become a trusted partner when it comes to delivering bespoke solutions.

This article first appeared in Mining Magazine December 2024