A new bolted-tank design is gaining momentum in tailings retreatment operations, offering significant improvements in cost savings, construction time and operational efficiency.

This design, developed by local steel fabricator Betterect Group, has been successfully implemented in various mining projects and is now recognised as a viable alternative to traditional welded tanks, Betterect CEO Nicolette Skjoldhammer tells Mining Weekly.

Using bolted tanks has played a pivotal role in the quick commissioning of gold miner Pan African Resources’ (PAR’s) Mogale Tailings Retreatment (MTR) project, in South Africa’s Gauteng province.

The bolted construction method reduces on-site labour requirements and accelerates project timelines while providing long-term maintenance and sustainability benefits for mining operations.

The design directly contributes to effective tailings management by ensuring that capital costs remain manageable, which is essential for projects to advance.

“You cannot effectively manage tailings if the capital project can’t get off the boardroom table,” adds Skjoldhammer.

Tanks also offer adaptability for future use, as its being bolted allows for stripping and reuse on other sites, making it 100% reusable and a more sustainable method over welded tanks.

This reusability reduces environmental impact, as the tanks can be dismantled using hand tools without emitting harmful gases, unlike welded tanks, which would require cutting equipment.

Betterect also ensures that all materials for the tanks, including the steel, rubber lining and bolts, are sourced locally in South Africa.

“We are firm believers in supporting the local South African supply chain wherever possible,” notes Skjoldhammer, emphasising that locally sourced materials not only reduce carbon emissions associated with transportation but also support the domestic economy.

Quick Turnaround

The operational advantages of the bolted tanks extend beyond sustainability, as most of the work is completed in a workshop environment, thereby enabling Betterect to mitigate the challenges typically associated with on-site construction of such large components.

“On a normal site, you generally get about six to seven productive hours a day. In some mining areas, it can be as low as four to five hours, owing to strict access controls. Compare that to a workshop environment with 24 available productive hours, and you can see why executing the work off-site is an absolute no-brainer,” she explains.

This controlled environment also enables the company to ensure higher quality standards. For instance, 100% of the welds on the tank, where required, undergo nondestructive testing, with zero defects often detected.

The initial tender for the project called for ten large carbon-in-leach tanks, 15.8 m in diameter and 17.4 m in height, to be welded on site, but they were reimagined by Betterect as fully bolted structures.

This innovation not only lowered the project’s capital costs but also significantly reduced the construction timeline, Skjoldhammer points out, adding that the shift to bolted tanks made the project a more attractive and viable investment for PAR.

The decision to use bolted tanks also had a direct impact on the project timeline, as PAR could commission the MTR plant several months ahead of schedule – a key factor recognised by MTR operations manager Oriel Shikwambana during the first gold pour ceremony, which took place on October 3, 2024.

Bringing the plant online early translated into additional gold production for the year, offering a significant financial advantage for the operation.

Addressing Processing Challenges

Tailings retreatment operations, such as MTR, have unique challenges, owing to the harsh and abrasive nature of the materials involved.

Betterect’s tanks were designed with these conditions in mind, and certified S355JR+AR material was used because of its strength and durability, while the tanks were lined with rubber specifically chosen to withstand the demanding process requirements and extend tank life.

The bolted connections are designed to be structurally sound, eliminating the need for any on-site welding.

The bolted tanks offer flexibility in terms of maintenance: if a section of a tank, known as a strake, becomes damaged or eroded, it can be easily replaced without significant downtime.

“A replacement strake can be fabricated off site, and the tank can be partially dismantled and quickly reassembled,” highlights Skjoldhammer.

She emphasises the scalability of the design, with there being “no limit to scaling this design for future projects”.

The company has also successfully implemented this modular approach in industries such as platinum, uranium and copper production.

Skjoldhammer believes that the success of the MTR project demonstrates the potential for bolted tanks to become a benchmark in the industry.

“By taking an innovative approach and engaging meaningfully with project partners, even projects that seemed unachievable can become low-risk and financially feasible,” she concludes.