Global Mining Review April 2023

Stephen

17 A Technological Transformation

Luca

20 A Productive Partnership In Idyllic Surroundings

Epiroc outlines how the iron ore mine at Noamundi, India, is taking productivity and sustainability to the next level.

23 The Solution Is Boring

Dennis Ofiara, Robbins, USA, details how non-circular tunnel boring can answer the need for the mechanical excavation of mine development tunnels.

27 An Electric Alternative

Gianfranco Conti and Lyndon Dean, Emerson, explain how electric actuators are quickly becoming a preferred alternative over pneumatic actuators for the mining industry, driven by advances in functionality and performance.

31 Fine-Tuning Frothy Waters

Quinton Sutherland, Weir Minerals, Canada, reviews how pumps can be utilised to solve the problems that occur in mineral froth tanks.

35 The Journey Of The Electric Submersible Dewatering Pump

Electric submersible pumps have a solid history in mining applications. Bart Duijvelaar, Atlas Copco Power and Flow, illustrates how the mining industry should rely on manufacturers that can provide the right solutions to meet mining challenges.

39 Improving Equipment Performance Through MPC

Kerryn Sakko and Grant McHenry, Rockwell Automation, Australia, discuss how machine-learning technology, and specifically model predictive control, can help mine and plant processes run closer to their constraints.

43 Go The Distance With Galvanisation

Burkhard Scherf, Thiele GmbH & Co. KG, Germany, considers how improved materials and galvanising on AFC-chains can promote better endurance and test results.

ON THE COVER

MMD Group is a global leader in the design and manufacture of Mineral Sizing and In-Pit Sizing and Conveying (IPSC) technology. The company’s groundbreaking fixed, semi-mobile (pictured) and fully mobile IPSC solutions are improving the performance and efficiency of numerous mines around the world by enhancing safety and reducing environmental impact, while delivering low operating and maintenance costs.

Guest Comment

2022 was marked by a plethora of tumultuous global events: from conflict to inflation, climate disasters, and market volatility. Despite these challenges, against the backdrop of a difficult economic climate, a recent study from Harvard indicates that the majority of institutional investors plan to increase their allocations to environmental, social, and governance (ESG) investments over the next two years.1 As these years unfold – and the challenges the world faces continue to be interconnected from an economic, political, social, and environmental standpoint – a wider range of focus areas will be seen coming into the ESG agenda for mining companies, supported by new environmental and sustainability performance targets, and far more stringent regulations.

MANAGING EDITOR

James Little james.little@globalminingreview.com

SENIOR EDITOR

Callum O’Reilly callum.oreilly@globalminingreview.com

EDITOR

Will Owen will.owen@globalminingreview.com

EDITORIAL ASSISTANT

Isabelle Keltie isabelle.keltie@globalminingreview.com

SALES DIRECTOR

Rod Hardy rod.hardy@globalminingreview.com

SALES MANAGER

Ryan Freeman ryan.freeman@globalminingreview.com

PRODUCTION MANAGER

Kyla Waller kyla.waller@globalminingreview.com

ADMINISTRATION MANAGER

Laura White laura.white@globalminingreview.com

EVENTS MANAGER

Louise Cameron louise.cameron@globalminingreview.com

EVENTS COORDINATOR

Stirling Viljoen stirling.viljoen@globalminingreview.com

DIGITAL ADMINISTRATOR

Leah Jones leah.jones@globalminingreview.com

DIGITAL CONTENT ASSISTANT

Merili Jurivete merili.jurivete@globalminingreview.com

Previously, the main drivers behind ESG initiatives were financial and corporate institutional concerns, or opportunities in response to sustainable development goals and regulations. The focus has largely been on the environmental aspects, with some further clarity required around expectations and measurable objectives on the social and governance agendas. Today, the focus is more on measuring ESG performance against a broader set of goals that satisfies the needs of all stakeholders.

Get this right, and mining companies with strong ESG performance will be in a position to reap the benefits of the competitive advantages ESG can deliver. Success, however, will be largely dependent on how the industry innovates together to make the possibility of ultra-efficient mines, that have a better interaction with nature, a reality.

Over the coming years, standards and regulations around social management practices are expected to evolve, with various industry and commodity-specific standards, principles, and protocols being developed. The Global Industry Standard on Tailings Management (GISTM) sets high expectations for community engagement, participation and collaboration, as well as socio-economic assessment alongside other International Council on Mining and Metals’ (ICMM’s) Performance Expectations.2,3

Whilst the extent to which ESG policies are being implemented in practice is still evolving, it is clear mining companies will be under ever-increasing scrutiny. A good example is the recent launch of the independent Global Tailings Management Institute (GTMI), to oversee implementation and conformance of the GISTM in the core areas of assurance, awareness, knowledge sharing, and disclosures. The GTMI will review how the standard is being applied across all operations, with transparency and independent verification.

While this is one example of a measurable performance accountability, there are many others.

Data management is a key area of focus. Better insights from data, using digital technology to manage, analyse, and utilise data allows mining companies to not only claim adherence to ESG initiatives, but also to provide evidence of their work practices.

When data is well-organised and easily accessible, it enables teams across a company’s operations to come together; creating opportunities for collaboration, bringing better insights, and driving improvements in ESG performance. With the right software and data management practices in place, companies are empowered to make better decisions and provide the evidence they need to demonstrate compliance. Transparency is key to reporting environmental performance, and it can only be achieved by wielding the power of accurate, reliable data. The challenge is that data often resides in different systems, architectures and platforms, making it difficult to break down silos and enable collaboration. By obtaining, combining, and analysing data from across a mine’s lifecycle, mining companies can easily demonstrate their commitment to sustainable operations.

Geoscience and engineering innovations continue to evolve to help deliver efficient mines, while minimising the environmental effects of waste during operations and following mine closures. Creating and working with accurate geological digital twins capable of handling large data sets and generating detailed models, mining companies can quickly visualise and interpret modelled data, allowing teams to connect, discuss and make decisions, even when they are in different parts of the world.

Sophisticated model management platforms, which provide a repository for all modelling data, can give operators easy and ready access to the information they need, when they need it.

Seequent is working hard to develop a deeper understanding of industry challenges, and deliver supporting technologies and workflows that help companies comply with stricter regulations. Technology is the key to supporting mining companies achieve and measure their ESG compliance, as well as implement more efficient practices across operations and better management of risk.

References

Available on request.

PIETER NEETHLING SEGMENT DIRECTOR MINING OPERATIONS, SEEQUENT

WORLD NEWS

Teck Resources and Agnico Eagle Mines have entered into a joint venture shareholders agreement whereby Agnico Eagle, through a wholly-owned Mexican subsidiary, has agreed to subscribe for a 50% interest in Minas de San Nicolás, S.A.P.I. de C.V. (MSN) for US$580 million, to be contributed as study and development costs are incurred by MSN.

For governance purposes, Agnico Eagle is deemed to be a 50% shareholder of MSN from closing, regardless of the number of shares that have been issued to Agnico Eagle or its subsidiary.

Teck and Agnico Eagle are now 50/50 joint venture partners at San Nicolás, working together to advance permitting

and development of the high-quality copper-zinc project, located in Zacatecas, Mexico. The joint venture partners are planning to submit an environmental impact assessment and permit application for San Nicolás in 1H23, and are targeting completion of a feasibility study in early 2024.

Concluding the San Nicolás joint venture, initiating permitting, and completing the next stage of technical studies is another positive step in Teck’s strategy to advance its industry leading Copper Growth portfolio in a timely and prudent manner; and for Agnico Eagle in leveraging its Mexican operating experience and know-how to pursue growth in a high-quality, copper-zinc mineral deposit located in a premier mining jurisdiction in Mexico.

AUSTRALIA Newmont to enter into confirmatory due diligence on Newcrest

Newmont Corp. has submitted a revised non-binding indicative proposal to the Board of Directors of Newcrest Mining Ltd to acquire 100% of the company’s issued share capital.

The acquisition is being undertaken by way of an Australian Scheme of Arrangement, under which Newcrest shareholders would receive 0.400 x Newmont shares per each Newcrest share held. In addition, Newcrest would have the right to fund and pay to its shareholders a special dividend of up to US$1.10 per Newcrest share. Newmont’s improved offer on these terms is best and final, subject only to no superior proposal emerging.

The Newcrest Board of Directors has agreed to grant Newmont confirmatory due diligence access to enable Newmont to put forward a binding proposal. Due diligence is expected to be completed within approximately four weeks. Newcrest has indicated that it intends to grant exclusivity to Newmont during the due diligence period, with the terms of that exclusivity still to be agreed. Newcrest will also undertake confirmatory due diligence on Newmont during this period.

Tom Palmer, President and CEO of Newmont, comments: “We are entering a new era in which mining companies must hold themselves to a higher standard of sustainability and long-term value creation. This transaction would strengthen our position as the world’s leading gold company by joining

two of the sector’s top senior gold producers and setting the new standard in safe, profitable and responsible mining.

“Together as the clear gold-mining leader, we would be well-positioned to generate strong, stable, and lasting returns with best-in-class sustainability performance for decades to come.”

The proposed combination creates the industry’s best portfolio of world-class assets with the highest concentration of top-tier operations, primarily in favourable, low-risk mining jurisdictions. Newmont would further strengthen its portfolio by increasing annual copper production, as well as adding nearly 50 billion lb of copper reserves and resources to its balanced and diverse asset base.

By applying Newmont’s long track record of safe and profitable mining, the combined group is expected to deliver significant annual synergies and create long-term value for all stakeholders. The business would be immediately supported by Newmont’s scalable, integrated operating model, with a deep bench of subject matter experts and existing regional platforms in Australia and Canada. This would allow the business to leverage the combined group’s global supply chain, and generate substantial synergies through the implementation of Newmont’s proven Full Potential continuous improvement programme.

MEXICO Teck and Agnico Eagle announce completion of the San Nicolás copper-zinc project joint venture

WORLD NEWS

Diary Dates

Expomin

24 – 27 April 2023

Santiago, Chile

www.expomin.cl

Mines and Money Connect: London 2023

25 – 26 April 2023

London, UK

https://minesandmoney.com/connect

CIMTL23 Convention and EXPO

30 April – 03 May 2023

Montreal, Canada

https://convention.cim.org

Discoveries 2023 Mining Conference

30 May – 01 June 2023

Mazatlán, Mexico

www.discoveriesconference.com

Mines and Money Connect: Melbourne 2023

14 – 15 June 2023

Melbourne, Australia

https://minesandmoney.com/melbourne

AIMEX 2023

05 – 07 September 2023

Sydney, Australia

www.aimex.com.au

China Coal & Mining Expo 2023

25 – 28 October 2023

Beijing, China

www.chinaminingcoal.com

To stay informed about upcoming industry events, visit Global Mining Review’s events page: www.globalminingreview.com/events

SOUTH AFRICA Epiroc completes acquisition of AARD Mining Equipment

Epiroc, a productivity and sustainability partner for the mining and infrastructure industries, has completed the acquisition of AARD Mining Equipment, a South African mining equipment manufacturer.

AARD, based near Johannesburg, South Africa, designs, manufactures, services and supports a wide range of mining equipment, specialising in low-profile underground machines for mines with low mining heights.

The company’s product offering includes drill rigs, bolters, loaders, scalers, and more. Its customers are mainly located in the Southern Africa region.

AARD has approximately 200 employees and had revenues in the fiscal year ending 30 June of approximately MSEK 650.

CHILE Sandvik expands its automation solutions at El Teniente

Codelco, the world’s largest copper producer, has chosen Sandvik Mining and Rock Solutions to supply its leading AutoMine® Fleet automation solution and 13 autonomous loaders for the Recursos Norte operations at the El Teniente mine in Chile. The contract will run from 2023 through 2027, supporting Codelco’s goal of operating the world’s most automated and digitalised mine.

This is a continuation of multiple automation solutions orders Sandvik has received from Codelco since 2019. After full implementation of the projects, Codelco will have more than 40 autonomous Sandvik trucks and loaders in operation at the El Teniente mine.

The new order will be supplied in two phases. During 2023, Codelco will receive six Toro™ LH514 loaders, as well as an AutoMine Fleet system capable of being scaled to support up to 13 machines and AutoMine production area hardware for future expansions over several years. Toro LH514 loaders belong to Sandvik’s mid-size offering with a 14 t payload capacity. The loaders’ reliability, robust structure, and Sandvik Intelligent Control System enable the use of highly advanced digital solutions, such as AutoMine.

The first phase of the order, which also includes support contracts for equipment maintenance, AutoMine lifecycle services and software licensing, will be used by Codelco Recursos Norte in a new block caving area in El Teniente. As a key productivity partner, Sandvik will support Codelco in its shift towards automated mining operations and increasing its workforce knowledge on these technologies.

The second phase of the order will be delivered from 2024 through 2027, in which Sandvik will provide seven more Toro LH514 loaders and an expansion for the AutoMine Fleet system.

the value of the domestic coal industry, as a result of prices dropping from record levels seen in 2022.

With the Biden administration focused on increasing the availability of critical minerals produced onshore to improve resource security, critical mineral production will be the driver of output growth in the coming years. Downward pressure from the US coal sector, however, will offset any increases to the mining industry value in the coming decade, with the US’ MIV set to decline by 15.5% from US$177.9 billion to US$150.3 billion in 2024, with an average annual rate of decline of 7.2% over the period 2024 – 2032.

The Americas: Key themes for 2023

Critical mineral projects to dominate pipeline with renewed focus on resource security

Analysis indicates a common theme playing out in the region is the rise in the development of critical mineral projects, such as copper and nickel, needed for the production of electric vehicles (EVs) and renewable energy grids. Global demand for critical minerals is set to rise significantly as the green energy transition accelerates. The race to secure sufficient supply of critical minerals as demand surges and deficits loom will encourage an influx of

new project investment across the Americas. Critical mineral project growth in the Americas will be buoyed by the IRA, which provides tax credits for EVs produced using critical minerals mined in the US or in US free trade partner countries. Canada, Peru, Chile, and Panama all hold free trade agreements with the US and have vast mineral reserves, providing upsides for countries across the region.

US-China tensions are putting pressure on authorities, in the US and Canada in particular, to introduce new policies targeted at reducing dependency on Chinese supply and the nation’s dominance in the market. The introduction of the Securing America’s Mineral Supply Chains Act of 2022, for example, aims to increase onshore critical mineral project development by simplifying the regulatory permitting process that allegedly stalls the development of new projects. The Canadian government is also implementing measures aimed to increase critical mineral production with the 30% Critical Mineral Exploration Tax Credit, applicable to critical minerals – including cobalt, copper, graphite, lithium and nickel, among others – to boost investment activity. Alongside this, are policies aimed at improving the national security of domestic resources. For example, the Investment Canada Act, introduced in October 2022, puts forth a new system to review investments into critical mineral projects by foreign state-owned companies and private investors closely linked with foreign governments. In late 2022, the Canadian government ordered three Chinese investors to divest holdings in Canadian listed lithium companies due to national security concerns.

As resource security becomes a key focus for major economies in the region, Fitch Solutions expects critical mineral output to grow across the region. Latin America holds vast, untapped mineral resources and will attract investors from the US as the Biden administration makes efforts to localise critical mineral supply chains.

Gold production set for steady growth

An influx of new gold projects will also drive future mining growth across the continent, with miners attracted to the region’s vast reserves and elevated gold prices. As evident in Figure 2, a healthy gold project pipeline will boost production in the coming years. Although Fitch Solutions’ analysis indicates that gold prices will gradually decline over the period 2023 – 2027, they will remain elevated compared to pre-pandemic levels and incentivise exploration activity.

Resource nationalism a growing threat to miners

Another trend Fitch Solutions expects to see across the region is a rise in resource nationalism, in response to the green energy transition and the influx of new projects. In 2022, a number of national governments, particularly in Latin America decided to either introduce new

Figure 2. Source: Fitch Solutions Global Mines Database.

Figure 1. e/f = Fitch Solutions estimate/forecast (Source: USGS, Fitch Solutions).

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policies to increase royalty rates or nationalise domestic critical mineral reserves. For example, in Chile, a new mining royalty bill increasing royalty rates on copper was approved in January this year by the Chilean mining and energy commission, and is now close to being passed. In April 2022, Mexico nationalised lithium mining, and has recently made a statement that the move was made to prevent exploitation of the nation’s rich lithium reserves.

Resource nationalism often creates an unfriendly investment environment as tax hikes negatively impact miners’ profitability, and the nationalisation of resources creates a difficult operating environment. In response to Chile’s proposal of a new mining royalty bill, major miners, who contribute significantly to the MIV, warned congress that the rate hike could lead them to reconsider their investment portfolios. BHP, for example, told congress that the proposed bill may lead them to examine their US$10 billion investment portfolio. In 2023, Fitch Solutions’ analysis suggests that the focus on resource nationalism from local governments could put downwards pressure on

investment activity in key Latin American nations – such as Mexico, Panama, and Chile – given the large volume of multinational miners operating in the space.

Heightened risk of community opposition and environmental protests in 2023

Fitch Solutions expects community and environmental opposition to pose a challenge for miners across the region in 2023, having the potential to significantly impede output volumes. Community opposition has long burdened miners across the region, with projects delayed as protestors raise concerns that mining activities will inflict harm on Indigenous communities and the environment. Additionally, local communities often argue they do not receive fair compensation for the inconveniences caused by miners. In 2022, for example, Southern Copper’s Cuajone mine in Peru halted operations as locals blocked access to water supply and key transport routes, claiming the company has not provided fair compensation to surrounding communities for the damage caused by mining activities.

Environmental protests will also present a challenge to miners. Environmental activists have often put a wrench in the cogs of mine development, and, with climate change a growing concern, miners in the region will have to continue to face issues during the permitting process, which may lead to delays to (or the rejection of) project plans. In the US, Northern Dynasty Minerals’ subsidiary Pebble’s copper-gold project in Alaska was blocked in January 2023 on account of the alleged harm the mine would cause to Bristol Bay, an area with a rich ecosystem. As of February 2023, activists in Nevada continue to fight against the construction of Lithium Americas’ Thacker Pass mine, situated on large lithium reserves needed for the production of EVs. As the number of new projects set to begin construction grows over the coming decade, alongside the acceleration of the green energy transition, Fitch Solutions expects to see an increase in opposition to mining activities across the region.

As a result, Fitch Solutions’ Industry Risk Score has declined in 2023 relative to 2022 levels for key markets across the region. Though the company is seeing governments actively focused on loosening permitting processes, environmental activists, and community opposition will continue to put downwards pressure on the likelihood of new mine developments coming online. This will present a major obstacle for miners in the coming years.

Notes

1. Represents mining gross value added (GVA). GVA measures the contribution to the industry of each individual producer. Simply put, GVA is the total of all revenues from final sales and(net) subsidies, which are incomes into businesses.

Figure 4. Note: Scores out of 100; higher score = more attractive market (Source: Fitch Solutions Mining Risk/Reward Index).

Figure 3. e/f = Fitch Solutions estimate/forecast (Source: Bloomberg, Fitch Solutions).

Stephen Gledhill, Freudenberg Filtration Technologies, Australia, explores how flexible filtration solutions can deliver hospital-grade air in enclosed spaces, subsequently reducing risks to mining personnel.

For centuries, mining valuable raw materials has been an important global economic driver. However, one of the most valuable resources underground is the health of mining vehicle operators. Modern filtration solutions can help ensure the safety of both staff and equipment. Especially multi-stage systems that meet the requirements of the ISO 23875 standard and can provide a viable solution for effective filtration and pressurisation monitoring in mining vehicles.

Mining is a profession that requires special attention to operator safety. Since the early days of the industry, miners have been exposed to hazards such as falling rock, overturning mining machinery, or even gas and dust-related explosions. Even after the introduction of safety and health regulations in the wake of mass mining during the Industrial Revolution, worker health too often played second fiddle to the rush for ever greater efficiency and productivity. The explosion at Cymmer Collier’s Old Pit in Wales in 1856 finally marked a turning point in the history of British mining and prompted Parliament to enact a comprehensive health and safety act for miners in 1860. The subsequent Mines Regulation Act of 1872 introduced further health and safety regulations for coal and non-metal mines into the law, which still forms the basis for legislation today.

A matter of value

Despite its difficult working conditions, the mining sector has grown considerably over the decades, with revenues for the world’s 40 largest mining companies totaling US$692 billion annually. 1 Fossil fuels such as coal, diesel, and iron ore continue to secure the world’s power grids. And entire industries rely on rare earths: not only are they essential to LEDs, PCs, and many smart devices. The alternative energies industry also relies heavily on resources buried deep beneath the earth’s surface to build state-of-the-art photovoltaic or wind power plants. With demand for these products remaining high, the sector’s growth is likely to remain vigorous. Protecting operators and equipment is hence of paramount

importance to secure mining’s long-term success, as hazards still abound underground.

From asbestos and silica, to pollutants from sand, coal and ash, aerosols can enter the cabins of mining vehicles – such as haul trucks, wheel loaders, and bulldozers –through ventilation slots, with sometimes fatal consequences: inhaled coal dust is a major cause of serious lung diseases such as pneumoconiosis (also known as ‘black lung’ or ‘miner’s lung’), tuberculosis, chronic bronchitis, and chronic obstructive pulmonary disease (COPD). In addition to these serious health risks, contaminated air also causes dust-related damage to mining vehicles, leading to premature mechanical and electrical failures. Therefore, international standards define strict operator safety criteria, giving rise to filtration innovations for challenging scenarios.

Meeting the requirements of ISO 23875

International standard ISO 23875 tightens the safety regulations for heavy equipment cabs and other operator enclosures in mining. It unifies the design, testing, operation and maintenance of air quality control systems, aiming for high filtration efficiency, limited CO 2 concentrations, and balanced pressurisation levels within mining vehicle enclosures.

What does this mean for mining site operators?

According to the ISO mining operator safety standard, fresh air supply and/or recirculated air must keep particulate matter concentrations below 25 mcg/m 3, while meeting pressure and CO 2 limits. Minimum continuous pressure in the driver's cabin is 20 Pa, with a maximum of 200 Pa. Likewise, the permissible CO 2 levels are strictly regulated: CO 2 concentrations inside mining vehicles must not exceed the ambient CO 2 plus 400 ppm. By comparison, the standard CO 2 present in the earth’s atmosphere ranges between 250 and 500 ppm.

And that’s not all: mine site operators are required to install a real-time monitoring system in the vehicles’ cabins, capable of alerting staff when CO 2 concentrations or pressure levels exceed

Figure 1. From asbestos and silica, to pollutants from sand, coal and ash, aerosols can enter the cabins of mining vehicles such as haul trucks, wheel loaders, and bulldozers through ventilation slots. Sometimes with fatal consequences.

9th International Conference on Tailings Management

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• Technical Courses given by the Co-organizer institutions: e Advanced Mining Technology Center (AMTC), Universidad de Chile; Tailings Center (Colorado School of Mines, Colorado State University & University of Arizona consortium), USA; TAILENG (Georgia Tech, Colorado State University, UC Berkeley & University of Illinois consortium), USA

• Networking Activities!

confirmed keynote presentations

tailing 2023 chair

kimberly morrison

Senior Director Global Tailings Managment, Newmont Mining Corporation, USA

geraldo paes

Global Director for Tailings, Vale, Brasil

phil newman

Head of Innovation, Anglo American, UK

priscilla nelson

Professor, Colorado School of Mines, USA

andrea lópez

Principal HDS Technology Development, Anglo American T&S, Chile

david machin

Tailings Strategy Senior

Manager, Antamina, Peru

More information in gecamin.com/tailings

their respective limits. Ensuring the health and safety of vehicle operators, as well as the functionality of mining equipment thus calls for filtration solutions capable of addressing several challenges at once. Leading specialists in air treatment for vehicle cabins have devised matching solutions that alleviate some of the extreme conditions to which miners are exposed in the field.

Technology for safe operations

Multi-stage filtration solutions with ISO 23875-compliant pressurisation and filtration of mining vehicle cabin air cover several requirements at once. Many vehicles only have basic air conditioning, offering zero or only inadequate systems for thorough dust filtration. Fine dust particles, for instance, can enter cabin enclosures via the miners’ clothing or boots, or as airborne particles when cabin doors are opened and closed. These particles subsequently remain in these confined spaces for a long period of time, as cabin air is often recirculated without proper filtration. Even retrofitted systems using filtered and compressed air usually do not meet the high ISO standard, which calls for filtration efficiency above 94% at 0.3

0.5 microns.

Futhermore, since the vehicles are sealed to achieve high cabin pressure, CO 2 easily remains in the cabin and quickly rises to dangerous levels in cases of insufficient air exchange. Fatigue, headaches, and nausea are the result – significantly increasing the risk of accidents underground.

Several stages of filtration

Multi-stage filtration systems offer a viable solution to prevent these situations altogether. They are often comprised of two pre-cleaning filters as well as two high-flow HEPA filters for effective particle separation. The two pre-cleaning elements protect the HEPA filters from heavy dust exposure and ensure longer filter life.

Air entering those systems first passes through a cyclonic dust ejection system that filters out heavy dust particles (>5 µm), before the second pre-cleaning filter takes care of coarse dust particles (1 – 5 µm). Two stages of HEPA filters then eliminate 99.995% of sub-micron particles, achieving a full cabin air exchange within 20 seconds. In addition to filtration of outside air entering the cabin, multi-stage filters also draw and filter air from within the cabin, ensuring cabins are dust free according to ISO 23875 requirements.

The HEPA-filtered air re-enters the vehicle cabin via the air vents into the occupants’ breathing zone, while also allowing some air to exit the system for fresh air exchange. Flexible filtration solutions can deliver hospital-grade air with ambient CO 2 levels and continuously monitor CO 2 levels in the vehicle and remotely via telemetry. With significant effects: fatigue and drowsiness due to high CO 2 concentrations no longer poses a risk to miners.

Protecting people and equipment

When it comes to sealed enclosures, maintaining the pressure inside the cabins while at the same time ensuring effective air circulation poses another challenge, which multi-stage solutions readily meet. They can provide a constant minimum cabin pressure of 100 Pa, which prevents contaminants from entering the interior from the outside, for example through worn door seals. In vehicles without an operator, they protect the electrical control units of autonomous vehicles, significantly reducing dust-related downtime and maintenance. HEPA filtration of the circulation air further protects air-conditioning components, such as fans and evaporative coils from dust-related damage – e.g. overheating due to clogged ventilation.

This is particularly interesting for sites that rely entirely on automated processes and equipment. The filtration systems transmit key data – such as temperatures, pressures, gas and dust values, as well as complete air conditioning parameters – via radio, satellite or 4G technology to any device, including mobile apps. Mine operators can analyse the data remotely to adjust the filtration systems accordingly. These monitoring devices can be used to maintain automated vehicles, as well as ensure the safety of staffed operations – perfectly compliant with the requirements of ISO 23875.

References

1. ‘Mine 2020: global Top 40 mining companies resilient in face of COVID-19’, PwC, (10 June 2020), www.pwc.com/gx/en/news-room/ press-releases/2020/mine-2020.html

Figure 2. Multi-stage systems that meet the requirements of the ISO 23875 standard provide a viable solution for effective filtration and pressurisation monitoring in mining vehicles.

Technological innovations are having a huge impact on global mining industry. Recent years have seen some New Zealand quarries adopting continuous surface mining technology to extract material instead of drilling and blasting or ripping with excavators, with impressive sustainability and productivity outcomes and reduced onsite labour and training requirements.

A compact and digital next-generation surface mining machine has improved operations at a Canterbury limestone quarry operated by Palmer Resources, New Zealand. The company became one of the first in this territory to begin using a dedicated surface mining machine, with the test and consequent adoption of a Tesmec 975 EVO Rock Hawg.

First of all, it is necessary to describe the context. The Palmer Resources limestone quarry is used for the extraction of calcareous material, and it is characterised by very variable hardness: from punctual analyses, the shear varies between 50 and 80 MPa, with a variable conformation from moderately to highly fractured.

As with all extractive sites, the primary objective of Palmer Resources in this quarry is to obtain sustainable production per cubic meter in terms of earnings, therefore it is necessary to:

n Extract as much volume of material as possible per shift.

n Avoid external contaminants (even if not entirely possible).

n Avoid scraps.

n Avoid downtime.

n Contain the cost of extraction.

For five years now, the extraction approach has consisted of using a modified cold milling machine with direct loading towards trucks/dumpers. Overall, the surface miner process improved significantly compared to what was previously used – such as drill and blasting and hammer excavators –both in terms of production and in terms of site time management. However, it had been noticed that using this equipment had two huge disadvantages. The first

A Technological Transformation

Luca Malpighi, Tesmec, Italy, highlights the upsides of continuous surface mining technology and how it has improved operations at a site in New Zealand.

disadvantage consists of the residual unexcavated material, due to the centrality of the rotating milling drum, with relevant repercussions on the productivity of the quarry: in fact, the potential extraction surface was reduced and made the quarry owner dependent on the use of other equipment for the removal of the unexcavated rock. Furthermore, the

operators complained that the machine was difficult to use due to its complexity.

A compact, digital, and efficient solution

After evaluating all the different solutions available on the market, Shaun Cleverley, Palmer Resources Group General Manager, opted for the 975 EVO Rock Hawg, the smallest surface miner model among the three members of the Tesmec Rock Hawg family.

The 975 EVO Rock Hawg is a 40 t class machine with a 375 hp CAT C9.3B US EPA Tier 4 Final / EU Stage V engine. The machine is equipped with a 2.9 m rear mounted drum that is larger than the tracks and allows the excavation of vertical walls and square corners, fixing the first issue. Its compact size makes it easily transportable from one site to another and improves manoeuvrability, even in narrow environments.

To answer the issue reported by Palmer Resources operators, the machine is equipped with digital and electronic systems for maximised excavation efficiency and ease of use:

n TrenchTronic, the user-friendly electronic system with an onboard HD display that eases machine operation and makes it less dependent on operator skill.

n TrenchIntel, the extra-high precision DGPS guidance system for automatic depth and grade control, autosteering to predefined path, pass optimisation, and fleet control.

n Re.M, the Remote Monitoring System for machine data remote monitoring, fleet location management, troubleshooting and operating conditions information.

EVO technology guarantees the best performance on hard and abrasive rocks, increasing productivity and decreasing teeth consumption and maintenance costs: the 975 EVO combines high chain pull and low chain speed thanks to its upgraded flywheels gearboxes and new hydraulic components.

By changing the attachment, the machine can operate in ‘upcutting mode’, discharging excavated material laterally with a conveyor belt; or in ‘downcutting mode’, with the drum leaving extracted material behind to be loaded onto trucks. Besides, this model has been conceived with a modular and versatile approach: the Rock Hawg-Chainsaw swap kit expands the application range by converting the 975 EVO to a hard rock trencher for utilities projects such as fibre optic, electric cables, water conduits, and pipelines.

Impact analysis

The introduction of the Tesmec 975 EVO RH model with drum mounted in downcutting mode has set a new standard for improving the mining process for Palmer Resources, which now consists of cultivating the entire available area of the quarry during one shift and loading the material during the next shift, which usually takes place at night.

In detail, the advantages of using the 975 EVO RH surface miner found by Shaun Cleverly in his New Zealand quarry are: n The drum position of the Tesmec surface miner allows 100% of the material to be extracted, thanks to its vertical walls.

Figure 2. The rear mounted drum of Tesmec 975 EVO RH is larger than the tracks and allows the excavation of vertical walls and square corners.

Figure 3. The Tesmec 975EVO RH can work both in upcutting and downcutting mode. In a first test, the drum was mounted in upcutting mode, discharging excavated material laterally with a conveyor belt. Palmer Resources opted for the downcutting mode, which best suited its site management.

Figure 1. A view of Canterbury limestone quarry operated by Palmer Resources, New Zealand.

n The size of the extracted material is such that the first screening and crushing phase is not necessary, with a consequent significant reduction in extraction costs.

n By not loading the excavated material immediately, the trucks are not obliged to be always at the disposal of the machinery; therefore, there is no waste of resources in that sense.

n The smart control technology of the machinery, equipped with the TrenchTronic 5.0 electronic system, is easy and intuitive for operators already accustomed to the use of excavators, which made it possible to increase staff turnover even without training support from the manufacturer.

n The compact size of the 975 EVO RH model allows it to be transferred to other Palmer Resources mining sites with relative ease and without significantly affecting operating costs.

n The implementation of the TrenchIntel system allows an orderly and safe cultivation of the quarry for the other vehicles.

Performance analysis

Generally speaking, the extraction process has improved in terms of organisation and impact on production costs, for the same amount of material extracted. With today’s diesel prices, the fuel savings of a surface miner have a very significant impact in terms of operating costs. Although a comparative analysis of the productivity data between the methods and models is not available, the data from this site’s experience suggests the 975 EVO RH can produce twice as much as a cold milling machine, with half the engine horsepower.

Another interesting fact concerns the unexpected performance of the machine at another Palmer Resources production site, where it was planned to be used for a week-long extraction; however, the work was successfully completed in just three days, with production peaks around 200 m3/hr.

The after-sales service and the local presence

The machine is equipped with the Re.M remote control

system, which allows remote monitoring and management, provides fault diagnostic data, productivity, and fundamental analytics for its optimal use.

Palmer Resources can take advantage of the remote support activities of the Tesmec assistance centre, which operates from the Grassobbio (Italy) headquarters, as if it were virtually sitting next to the operator in the cab, in order to optimise the management and maintenance of the vehicle. If necessary, the assistance service is available to offer ad hoc service and training opportunities for future new operators of the New Zealand quarry.

Conclusions

Overall, the technical concept of this Tesmec compact surface miner is appreciated and provides the opportunity to work smarter, not harder. Nonetheless, there could be significant opportunities for this technology to transform the New Zealand and Pacific markets in an unprecedented way.

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A productive partnership in idyllic surroundings

Epiroc outlines how the iron ore mine at Noamundi, India, is taking productivity and sustainability to the next level.

Figure 1. The SmartROC D65 offers precise capability in terms of providing the drilling data, enabling accurate drilling and blasting.

Green landscapes, fresh air, a tranquil atmosphere, vast open farmlands, followed by lush forest areas… the five-hour drive from Ranchi airport, in the state of Jharkhand, to the Noamundi mine is a treat for the senses. Closer to the site, the surroundings are green and serene, seemingly unaffected by almost a hundred years of mining.

Indeed, it was in 1926 that iron ore was discovered close to Noamundi, a town located roughly 130 km from Jamshedpur. Today, Tata Steel, one of the top steel manufacturers in the world, produces approximately 30 million tpy of iron ore from its ore mines and quarries division (OMQ), consisting of four mines: Noamundi, Katamati, Joda East, and Khondbond. The Noamundi mine never ceases to operate, and activities are carried out in three shifts per day.

Progress through new technologies

Much like any mine operator, Tata Steel rates equipment reliability, availability, and productivity as success factors for uninterrupted mining. To ensure productivity and safety, and to enhance its digital mining capability, the company commissioned Epiroc’s SmartROC D65 surface drill rig and the BenchREMOTE operator station at Noamundi in 2020.

Arriving at the mining site, the sturdy SmartROC D65 is clearly visible in operation at the centre of the captive iron ore resource, but not its operator. They are seated in the BenchREMOTE operator station, approximately 100 m away. While the SmartROC D65 provides high-quality drilling, enabling accurate blasting and fragmentation, the BenchREMOTE helps safeguard operators’ safety by keeping them away from any potential hazards surrounding the rig. It also drives productivity and elevates drilling performance.

Enhanced operations

Sanjit Kumar Adhya, Head of Operations at the Noamundi mine, has said that since Tata Steel’s focus is digital, and that it is solutions like this that help take mines to the next level. The SmartROC D65 rig can achieve a penetration rate of 2 m/min., and an average drill rate of 35 m/hr in hard sedimentary iron ore strata.

From interactions with the onsite team, and further delving into the automated rig’s advanced features – such as ‘full drill cycle automation’ and ‘hole navigation system’ – AJ George, Head of Equipment Maintenance at Noamundi & Katamati Iron Mine, affirms that these features have helped the systems and operations group improve its performance.

The hole navigation system guides the machine, and the level of accuracy is high enough to determine the rig’s position within 10 cm. The depth to which it drills is controlled precisely, leading to clearly observable benefits for blasting operations in mines such as Noamundi.

Another important Epiroc solution is ‘measure while drilling’. A lot of data, including the properties of the rock, is generated while drilling, and several parameters are captured. With all data directed to one platform, it can be used for predictive analysis to identify areas that need attention. This feature also helps detect the precise location for drilling.

Furthermore, a peek into the operator cabin reveals a touchless screen, which displays every minute detail about

the drilling activity. The cabin is air-conditioned and spacious enough for the operator to be comfortably seated, and operator safety is paramount. According to Bira Soren, Senior Drill Operator, while previously used machines had to be operated manually, the SmartROC D65 is supported by an

automated system. The machine can drill to the metre setting, which improves operations as well as safety. Soren is also a strong advocate for the comfort and safety of the BenchREMOTE, distanced from the machine. At the Noamundi mine, the operator station has been prepped for one operator to operate three machines at a time, made possible by the fact that they are all in auto drilling mode.

Training

The saying goes that there is no end to learning and training, and this holds true for Tata Steel’s operations at the Noamundi mine site. Whenever there is a new product or technology available, training is mandatory. Here, too, training has been offered from the manager down to the line field operations team.

Safety

Introducing and operating new technologies bring challenges, but the SmartROC D65 and BenchREMOTE were warmly welcomed by Tata Steel and its employees, as they would help enhance productivity and achieve higher safety standards.

For Tata Steel to get the most out of the equipment, Epiroc personnel are present year round at the Noamundi mine. Since this is the first deployment of this kind of technology in India, there could be operational challenges. To address them, Epiroc has trained the customer at different levels, including the operators. Problems are analysed daily, and training plans are put together accordingly.

Monitoring and maintenance

To ensure best service and minimum downtime, Epiroc has developed several monitoring systems – the life of every component is measured and parts are arranged accordingly. This results in immediate replacement in the event of a breakdown of any component, be it in the rig or the BenchREMOTE. To ensure such timeliness, a service and maintenance team is visibly stationed onsite, and machines and components are serviced and checked. While this is located in the mine site area, it is still away from the main area of mining activity.

Conclusion

Tata Steel’s service agreement with Epiroc has proved very valuable. One example of this value is that it has helped with enhancing and improving the drilling meterage per month. In terms of maintenance, spare parts and inventory – and to ensure a smooth supply chain process – Tata Steel has also entered a Vendor Management Inventory (VMI) contract with Epiroc. Selling is a sacred trust between buyer and seller, and this is evident onsite when you see the Epiroc and Tata Steel teams interacting with each other. It is no wonder this trust has prevailed between both companies for over 30 years.

There have been mutual discussions between Tata Steel and Epiroc over the years to improve safety features. The performance of Epiroc’s equipment has impressed greatly, and thus Tata Steel has taken a step forward on digital and remote operations with the adoption of BenchREMOTE. Performing such activities remotely, away from

workplace,

the

is the next step.

Figure 2. Thanks to the BenchREMOTE operator station, the drill rig can be safely operated from up to 100 m away, eliminating the need for operators and surveyors to work in hazardous areas.

Figure 3. Epiroc’s Rig Control System (RCS) is at the core of onboard automation solutions for surface drill rigs. The SmartROC D65 has a graphical interface with a touch screen inside the comfortable air-conditioned FOPS and ROPS-certified cabin.

Figure 4. Intelligent, automated and with improved fuel consumption, the SmartROC D65 has features described by AJ George, Head of Equipment Maintenance, as: “a delight for the maintenance engineer and operator because the information is available online and, in most cases, real time.”

Dennis Ofiara, Robbins, USA, details how non-circular tunnel boring can answer the need for the mechanical excavation of mine development tunnels.

There are many thousands of kilometers of mine development tunnels driven in rock each year. Currently, most of these tunnels are excavated by the drill and blast technique. This technology has advanced, with more effective drilling, loading, support, and muck removal equipment. However, the process is still cyclic and slow compared to TBM excavation rates. Blasting is inherently dangerous and causes delays for mine evacuation, equipment movements, fume removal, etc.

Mining is becoming more challenging. Mines are getting deeper, or farther from the shaft or portal, and are often in more difficult geology. Modern society will not accept hazardous working conditions, and desires sustainable and carbon neutral industrial production. There are many plans for autonomous mining, with as few people as possible routinely underground. Indeed, some autonomous underground mining equipment and operations have already been implemented.

This, and all the other factors already noted, has accelerated the age-old desire for mechanical excavation of mine tunnels. The mining industry would like to achieve the progress rates and efficiency achieved by the civil tunneling industry when using TBMs for tunnel excavation. However, there are many difficulties and demands that are unique to the mining industry. These must be recognised, addressed, or re-thought for a mechanical excavation system to be successful for mining.

Mine tunnels: rectangular or circular profile

The mine industry usually demands rectangular, or flat-bottomed tunnels to enable use of a rubber-tired mining equipment fleet. There have been some exceptions, where the mine accepted a circular tunnel profile. Some of these have been coal mine entry slopes, such as Australia’s Grosvenor and the UK’s Selby Coal Mines. Some metal mines have accepted the circular profile and have effectively used TBMs. These include White Pine Copper, Magma Copper, and Stillwater Mine, where four circular TBMs have been utilised. However, the mining industry generally demands tunnels with a flat bottom.

The two cross sections shown in Figure 1 compare a circular cross section to a rectangular profile.

A rectangular cross section of 5 m W x 4.5 m H will accommodate a 30 t mine truck. In order to provide a similar roadway width, the circular tunnel would need to be approximately 6.5 m diameter. That is a lot of wasted excavation and more material to remove from the mine.

In the circular tunnel, the flat roadway must be created by laying a precast concrete invert or slab, or by partial filling and compacting. These are expensive secondary operations.

It is easy to see the attraction of the rectangular profile, for most mining requirements.

Historical efforts for flat bottom mechanical excavation

Mechanical rock excavation machines have been under development for many, many decades. Most of these efforts have been for circular machines. However, several efforts have been made to provide a rock excavation machine that could produce a rectangular, or flat bottom profile.

Figure 3. Mobile Miner TBM, which cut a near rectangular profile.

Figure 1. Circular and rectangular tunnel comparison. The rectangular tunnel has 32% less volume.

Figure 2. Mini Full-Facer non-circular TBM.

One such non-circular machine was the Atlas Copco Mini-Fullfacer, shown in Figure 2, produced in the 1970s and 1980s. This machine had a swinging drum with a rotary cutterhead that was dressed with robust carbide milling type teeth. A more or less flat bottom profile with an arched roof was produced. This cross section was useful for small pipe and utility tunnels. However, in harder rock the carbide teeth needed frequent replacement, which proved to be the nemesis of these machines.

Some of these Full-Facer machines were produced that had four such rotating cutterheads and could produce a 4.8 m rectangular profile. It is interesting to note that the Full-Facer machine geometry is similar to the MDM5000 mentioned later. There is a robust front gripper that the cutterhead swings about, and a rear gripper on the machine frame.

the cut. This limits the thrust that is delivered to the rock face, in spite of the high numbers of cutters installed.

Developmental history, Robbins MDM5000

The creation of the MDM5000 (Mine Development Machine) in recent years was the result of a long collaboration between Mina Fresnillo in Zacatecas, Mexico, and Robbins. This silver mine is one of the oldest mines in the world, operating since early colonial times. Fresnillo has always embraced technical innovation, even utilising an original Watts steam engine to dewater the mine, when this was new, bold technology.

Fresnillo was eager to consider mechanical methods to drive mine development tunnels. Robbins collaborated with Fresnillo and AMC mine consultants to study the

cross section developmental tunnels. As these discussions evolved, Robbins presented a concept for disc cutter mechanical excavation to produce a rectangular cross section. This was based on a ‘swing arm’ type machine. The concept was based on machine designs that used a swing motion of the cutterhead to produce a rectangular cut. This concept was originally developed in

the 1990s by retired, but active, Robbins engineers John Gibson and Andy Anderson. The effort was to develop a machine to mine rectangular drives in the platinum ore veins, known as ‘reefs’ (Figure 4). These reef miners cut a 1 m H x 5 m W tunnel within the platinum ore reef.

The reef miners had a cutterhead that swung about a vertical axis. Muck removal was handled by a vacuum system. The reef miner did cut, but was considered low priority in the context of the entire mine operation. This seems to be a typical outcome when promising technology is given a rather short-term review, and lack of commitment.

This reef miner concept formed the basis for the MDM5000 design. The reef miner swung the cutterhead about a vertical axis and used vacuum muck removal. For the MDM, the judgement was made that swinging about a horizontal axis was preferred. This prevented gripping on the crown, which could be risky in poor ground conditions. The large front gripper of the MDM serves as the swing axis for the MDM cutterhead. This avoids gripping on the crown, provides good stabilisation of the cutterhead, and allows the swing motion of the cutterhead to scrape the excavated muck up onto an apron for disposal by a chain conveyor within the MDM.

As the MDM was designed, many coordination meetings were held between Fresnillo, Robbins, and Topo Machinery. Topo is the local Robbins agent who operates the MDM. This coordination and commitment is vital and continues today.

The MDM was manufactured by Robbins and delivered to the mine. The machine was taken on a tracked carrier 7 km underground on the mine ramp road. It was transported in three main modules that were essentially driven into one another and bolted up. No heavy hoists or large chamber was needed at the launch site. A view of the MDM and the tunnel that it produces are shown in Figure 5 and 6, respectively. The machine is a ‘tunnel factory’. A finished tunnel is produced with a smooth roadway, roof support, vent line, tunnel conveyor, and life-of-mine piping all installed in a single operation.

To date, the MDM has cut approximately 1.7 km of tunnel. It has produced at rates of up to 191 m per month, which is very favourable compared to drill and blast. The machine is currently being relaunched and a second tunnel about 4 km long is planned.

Future flat bottom mechanical excavation, MDM, and other machines

The mines certainly approve of the profile excavated by the MDM. There is demand for this kind of equipment. Robbins is making efforts to improve the productivity of the MDM by increased cutter capacity, faster swing cycle, and other improvements.

In addition, Robbins has developed a design for a circular TBM that can produce a horse-shoe shaped profile. This machine should provide advance rates comparable to conventional circular hard rock TBMs. The continuous rotary motion of the TBM type machine will excavate faster than the cyclic swing motion of the MDM.

Figure 5. MDM5000 Rectangular Machine.

Figure 6. Rectangular tunnel 5 m W x 4.5 m H produced by the MDM5000.

Figure 4. Reef miner cutting 1 m x 5 m rectangular opening.

Gianfranco Conti and Lyndon Dean, Emerson, explain how electric actuators are quickly becoming a preferred alternative over pneumatic actuators for the mining industry, driven by advances in functionality and performance.

The worldwide drive for electric cars has driven a global demand for lithium and other rare earth metals. However, the same environmental, social, and governance (ESG) trends that are pushing for electric vehicles are also being applied to mining operations, forcing the industry to improve its own ESG efforts, even as it expands and grows to meet burgeoning mineral demands.

This article explains the role electric valve actuation plays in achieving mining ESG goals, and it discusses the selection criteria that drive the decision between traditional pneumatic and electric valve actuators.

A changing environment

The increasing focus on decarbonisation and sustainable commerce across all industries is driving a multitude of market changes, including: a transition to electric vehicles, increased green energy production, and more efficient electrical devices. Since these technologies require rare earth metals and lithium, mining efforts to recover those products have accelerated in response.

Of course, the same ESG forces driving these changes are being applied to the mining industry as well. It is not acceptable to address one environmental problem by creating another, so the mining industry is forced to reassess what has always been done by thinking in new and more environmentally conscious ways.

In addition to these challenges, the mining industry also faces difficulties associated with reduced staff, water scarcity, remote locations, and high operating costs. A mine must operate continuously and efficiently to be financially successful, so equipment reliability and long-term operating costs are critical for long-term viability.

Valve actuation decisions

Automated valves play a large part in mining and ore processing. Historically, hydraulic valves have been utilised for high-pressure applications, and pneumatic valves have been used for nearly everything else. Until recently, electric valves captured very little of the market due to their limited torque and lack of a fail-safe response on power loss.

However, pneumatic valves have limitations as well. They require a source of high-quality air, which can be difficult to supply in remote applications. They also tend to be less reliable in the long term, especially if the quality of the air is not carefully monitored and maintained. Regardless, pneumatics have historically dominated because electric valves simply could not meet the demands of the applications.

That thinking is changing due to recent improvements in electric actuation technology. Electric actuators can now generate the torque and speed

requirements required for most applications, and some actuators can now be fail-safe.

While electric actuators can be more expensive initially for some applications, they tend to cost less when one considers the operational cost of the air system itself, along with the pneumatic actuator expense. Electric actuators also tend to have better reliability in the long term, requiring less maintenance and repair.

Which actuator is best?

Like any other technology, both pneumatic actuators and electric actuators have their advantages and disadvantages. The best choice depends upon a number of factors.

Pneumatic actuators may cost less initially, but more over time; with operating costs varying depending on the size and utilisation of the compressed air system. A well-sized air compressor and distribution system provides comparatively low operating costs, but an oversized or poorly maintained compressed air system will result in very high operating costs.

The technology itself is not efficient when one considers the cost of treating and compressing the air, which is exhausted with each stroke. Pneumatic actuators tend to be smaller for a given torque size, but are not inherently good at positioning, so more expensive positioners are required to achieve tight valve position control. These same positioners can also provide advanced diagnostics and remote connectivity, but that functionality comes at an added cost.

Pneumatic Electric

- Initial cost lower but lifecycle cost higher.

- Operating costs tied to compressor size and utilisation.

- Tight positioning options significantly raise cost.

- Higher failure rate due to solenoid, tubing, positioner, and dependence on air.

- Partial stroke testing possible with add-on.

- Advanced diagnostics and connectivity available as options, but supply of electric power required.

- Winter freezing possible with poor air quality.

- Stroke can be controlled, torque control limited.

- Configuration tied to hardware calibration, so fast changeover is not typically feasible.

- Reliable operation dependent on air supply pressure/quality.

- Initial cost higher, but lifecycle cost lower.

- Efficient operation.

- Very fine positioning possible.

Design enhancements have made electric actuators much more competitive (Table 1), but they are inherently more efficient. They may cost more initially, but over time the improved reliability and independence from an air system make them less expensive to operate. Very precise positioning and advanced torque control are usually part of the actuation package, allowing the valve to execute any number of positioning and torque profiles. Different profiles can be stored and remotely executed, allowing an electric valve to alter its characteristics quickly and easily. Advanced diagnostics and connectivity are usually part of the standard electrical actuator package, providing further advantages in terms of reduced maintenance costs and increased uptime.

- Significantly reduced failure rate.

- Integrated feedback and partial stroke testing.

- Advanced diagnostics and connectivity easy to include.

- Operates reliably down to -50˚F.

- Fully adjustable stroke and torque options.

- Altered configuration can be downloaded, providing fast changeover options.

- Can run on solar batteries in remote areas.

- Requires only electricity.

Historically, the lack of a fail-safe position drove many users to choose pneumatics over electrical actuators. The introduction of spring return electric fail-safe actuators allows electric actuators to achieve SIL 3 safety

Table 1. Significant advances in electric actuator functionality and performance have altered the economic landscape for valve actuation selection

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shutdown ratings, while providing a predictable response should power be lost.

Electric actuator designs have improved dramatically in recent years, and the diagnostic capabilities of modern valve actuators can be used to monitor and improve valve and actuator performance.

Both actuation technologies can be connected to a host system, via wired or wireless digital networks (using an adapter), reducing installation costs when valves are spread across a large area. WirelessHART TM networks are self-configuring and self-healing, providing advantages over some competing wireless technologies.

Electrically actuated valves are particularly well suited for wireless applications, since power is always available. However, a battery-backed power module in an electrically actuated valve can allow it to continue to broadcast valve position data wirelessly, even if the main power supply is lost.

Picking the right option

The best technology often depends upon the relative size of the valve, along with the existence of a compressed air system. If a pressurised air system already exists, adding a few more pneumatic valves to it is most likely the best choice. In a greenfield application, an all-electric actuation solution may well be the better option, especially when the capital and operational cost of a new compressed air system is factored into the decision. A large capital expansion might also favour electric valves, if the addition of valves will require a major upgrade to the existing air compressor or air header system.

Some other factors that may impact the decision include:

n A requirement for variable stroke/torque profiles or very precise positioning.

n The ability to power smaller electric actuators with solar power in remote applications.

n Water constrained environments may not allow low-cost water cooling to run the air compressor, increasing operating costs.

n Availability of skilled personnel to maintain pneumatic valves and associated compressed air systems.

Electric valves in mining service

In one application, a mine utilised a solar powered solution to control a remotely located off-the-grid water truck fill station. Running air or electrical lines was cost prohibitive, but a solar powered electrically actuated valve solution allowed the system to be remotely controlled and monitored, improving operating efficiency.

Recent regulatory changes in Chile require all new mines to provide their own water supply, so many mining operators are installing desalination plants (Figure 1).

The dusty, salt laden environment for these projects makes the cost of running and maintaining a compressed air system very high, so many mining operations are utilising all electric valves to reduce operating costs

A third mining site is utilising electrical valves for a significant portion of their operation. In a bid to go carbon neutral by 2030, the company is employing electric valves as part of a site wide system of solar power to achieve their ESG goals. The advanced diagnostics and higher efficiency of the electric actuators are expected to reduce energy utilisation, while significantly cutting operating costs due to reduced required maintenance and increased uptime.

Conclusion

Recent design advances have provided improved reliability and functionality, altering the decision landscape for pneumatic versus electric actuators. While the ultimate decision will depend upon the existing infrastructure and specific application, electrically actuated valves are increasingly becoming a financially superior option for many mining applications.

When faced with a major control upgrade, it is worth taking the time to discuss the options with the automation vendor and investigate the latest valve actuation alternatives. While pneumatic actuators have historically been the only acceptable choice, there are now other options worthy of consideration.

Figure 1. Greenfield desalination plants often use all electric valve actuators instead of pneumatics. While initially more expensive, the operating costs for electric valves is substantially less in this application.

Fine-tuning frothy waters

complicates suction conditions, and can result in an air lock condition at the impeller eye. The slurry at the eye of the impeller is at a lower pressure than the slurry at the pump discharge and, since fluids and gases move from high pressure to low pressure areas, the air entrained in the slurry builds up in the impeller eye and can block the pump from pumping.

Understanding mineral froths

Mineral froths can range from brittle on one end of the spectrum, consisting of large bubbles that break easily, to tenacious on the other end of the spectrum, consisting of small bubbles that can remain in the liquid for many hours. The characteristics of the froth can change frequently depending on the varying process parameters. Combinations of various flotation

techniques push the limits of the flotation process, in order to recover more of the valuable minerals and improve flotation process efficiency. This can result in a mineral froth with a high froth volume factor (FVF), which is a measure of the air contained in the froth, defined as the ratio between initial mineral froth volume and final slurry volume after the sample is left to de-aerate for 24 hours:

Pumping froth is challenging and requires specialist equipment. Depending on the application and existing plant, operators can select from a range of both vertical and horizontal froth pumps.

Pump evolution

In the past, Weir Minerals’ Warman® AF vertical pumps were a common sight in flotation circuits around the world. However, as flotation technology has evolved the requirement to meet larger plant throughputs and process demands have increased, it has become impractical for the traditional vertical froth tank design to increase in size to meet tonnage and flow performance demands.

In the 1980s, Warman design engineers began experimenting with the Warman AH slurry pump to manage mineral froth in hard rock processing sites in Queensland, Australia. These trials led to the development of the Warman AHF™. After further work, this offering was expanded to include the range of Warman MF and LF froth pumps, featuring a large suction and open scoop impeller, which prevents air gathering in the pump. These pumps can accommodate most froth pumping applications; however, in the instance where the froth is particularly tenacious and/or has a high FVF, pumps with a non-vented froth impeller can still become air locked, causing surging and unstable pump performance. The operator can try to reduce the FVF in the suction tank before the froth gets to the pump, but these measures are often cost prohibitive.

Weir Minerals developed a solution utilising the pump itself to separate and remove the entrained air from the froth slurry. The Warman horizontal froth pump Continuous Air Removal System (CARS) design features an impeller that has back expelling vanes and back shroud vent holes. The venting system also includes a gas collection chamber with a flow inducer behind the main impeller. The flow inducer facilitates the flow of separated air through the vent pipe and out of the pump. As the inducer vanes apply a swirl effect, the heavier (compressed) portion of the mixture centrifuges to the outer periphery of the pump, which forces the free air towards the middle. The air passes through the vent holes in the back shroud of the impeller into the collection

Figure 1. Warman AHF™ pump with CARS at the Vale Salobo copper mine in Brazil.

Figure 2. Warman AHF heavy-duty froth pump with CARS.

chamber where the flow inducer forces the air out through the vent pipe.

Process optimisation

Vale’s Salobo copper mine in Brazil was having problems with its tank leaking and overflowing –resulting in material loss and increased plant shutdowns.

The installed Warman AHF froth pump at Salobo was originally designed to pump froth with an FVF of 2.0. However, due to process changes, the FVF oscillated between 1.3 and 2.4. When this interval ranged from 2.0 – 2.4, tank overflows were frequent.

The solution to pumping mineral froth with high FVFs and reducing tank overflow is to reduce the amount of air in the slurry and instead create volume-generating froth. Thus, CARS technology was added to the three existing Warman AHF froth pumps and this solution was trialled for 90 days. The existing pump configuration was modified to accommodate the CARS components, and a maximum limit FVF of up to 1.7 was set for the trial period.

The Warman AHF froth pumps with CARS removed air from the unrelenting froth and reduced the rate of overflows at each of the tanks by 66%, 19.36%, and 9.93% respectively (data collected at box level above 90%). With the implementation of CARS, the Warman AHF froth pumps now achieve a considerately lower FVF of 1.1, while tank overflows have also decreased.

Additionally, the performance of the pumps has significantly improved and the site no longer needs to operate all three pumps. It now operates two Warman AHF pumps with CARS and uses the third pump as a standby. What had been a constant struggle for operators is now an easily managed process.

Improved efficiency and pump performance along with reduction in material losses and unplanned shutdowns has saved Vale Salobo more than US$135 000 per month, a total savings of US$1.6 million per year.

Pump and plant selection

There are a lot of unknowns when it comes to froth pumping, which can make pump selection challenging. Weir Minerals works closely with each mine’s metallurgists to collect and test slurry samples. Typically, the volume of the sample is measured using a graduated cylinder; it is left to sit for 24 hours and then re-measured. The differential between the two measurements is how much air is contained in the slurry, having dissipated in that time. This same experiment is repeated on a number of samples, providing an average FVF value that is then used to determine the most suitable pump.

In addition to the pump itself, there are a number of other important design features to consider. The discharge pipe needs to be positioned at the top of the pump, or at a 45˚ angle to ensure the air trapped at the top of the casing has a way to escape the pump.

It is also important to ensure that the motor is sized appropriately. It is a good idea to make sure the drive system has enough power to handle any upset or potential high flow cases that may not have been seen when the samples were taken.

Furthermore, hoppers should be designed to reduce FVF, or at least maintain the FVF of the mineral froth feeding into the hopper. The most important design features should include a long retention time –approximately 60 seconds, but no less than 30 seconds – to allow some of the air to dissipate before entering the pump; tangential feed to minimise turbulence and ensure unnecessary bubbles and air are not introduced, while encouraging the air to gather at the centre where it can escape to atmosphere; and a conical tank shape, rather than a flat or rounded floor, further improves the flow of minerals and froth into the pump.

Collaboration

At the end of the day, froth pumping remains a significant engineering challenge for both miners and pump manufacturers. Incorrect pump selection and operation or a poorly designed plant can cause unstable pump performance, resulting in unplanned downtime and lost production. It is by working together –understanding the miner’s operational requirements and leveraging the OEMs specialist technical knowledge –that the best outcomes are achieved.

Figure 3. Slurry box overflow.

The journey of the electric submersible dewatering pump

Electric submersible pumps have a solid history in mining applications.

Bart Duijvelaar, Atlas Copco Power and Flow, illustrates how the mining industry should rely on manufacturers that can provide the right solutions to meet mining challenges.

The WEDA range of submersible dewatering pumps is designed with the latest pumping technology to meet customer needs on compactness and durability while addressing application needs for managing highly abrasive materials and solids. The drainage, sludge, and slurry pumps are well-suited for mining applications and are built with advanced high-wear resistance impellers for longer pump performance. With new technology upgrades and sustainable

pump designs in the pipeline, it is important to focus on the most innovative and customer-focused pumping solutions in mining and other applications.

Rethinking pump technology and design

What used to be considered okay as a lifetime for an electric submersible drainage pump is now held to higher standards.

On top of that, sustainability considerations require submersible pumps to be economically viable to repair to a larger extent than ever before. This fundamentally changes the way submersible pump manufacturers must think. Repairability needs to be factored into the design from the first sketches of a new pump design. However, this sometimes conflicts with manufacturability. One of the absolute best ways to avoid repairs is to extend the service intervals.

It is a hard day’s work for pumps in mining applications

Unique to mining, compared to many other applications, is the incredibly abrasive and harsh working environments pumps are exposed to. Apart from hydraulic challenges in

pump design, such as avoiding wear hot spots, the pumps need to be robust, in order to to survive the unavoidable rough handling that is part of everyday life in an active and ever-changing mining environment. These requirements may be at odds with other important design aspects for submersible dewatering pumps in mining applications, such as transportability.

It is one thing to carry a 30 kg (67 lb) pump when standing upright, with your arm straight, not having to provide more muscle strength than needed to grasp the handle. But, if the pump is tall enough that one is forced to bend their arm, this can suddenly become very heavy to carry around. Add to that the very cramped spaces typical for underground tunneling jobs, it becomes even more obvious that the degrees of freedom for designing a lightweight, small-form-factor, robust, and wear-resistant submersible drainage pump are heavily reduced.

And that is only the pump. Electric submersible pumps need power cables and, in some cases, start and motor protection panels that add to the complexity of moving a pump with its long cable plus bulky starter panel around in cramped spaces, with limited lifting devices.

Gearing up for the changing requirements

Only very few global submersible pump manufacturers can combine all of the above design requirements. Especially since the product design lifecycle for submersible pumps easily stretches over decades, it is important to look at what upgrades can be made by using submersible pumps that were designed in the past 5 years, for example.

Today’s submersible pump design engineers have at their disposal tools that were inconceivable only 5 or 10 years ago: advances in cloud computing have made computational fluid dynamics (CFD) simulations more scalable than ever; 3D-printing techniques allow for rapid prototyping; and many development iterations can be made before the product design deadline imposes itself. Furthermore, geometries that were hard, or even impossible, to cast 10 years ago, can today be reliably cast. This is due to advances in the techniques making use of casting cores and moulds that are (partly) 3D-printed.

All of the above are only as good as the after-market support that will inevitably be required to keep the pumps running for the extended periods of time that mining operations demand. Choosing a global brand of submersible pumps with the ability to develop new products, but also provide spares and support to products for their entire service life is more important than ever. Global electric pump suppliers will be better equipped to keep track of changes and advances in pump technology and implement those improvements in the product range.

Global players are often better positioned to find top-of-the-line fully-fledged local partners, such as resellers and distributors, that are not merely selling a product, but selling solutions, pre-sales product selection, technical training, warranty support, and, last but not least, maintaining a local stock of products and spares. Smaller players will usually not be able to attract many of the companies on regional markets that are actually able to

Figure 1. Built for the toughest job sites, the WEDA dewatering pump works efficiently in an underground mine.

Figure 2. Compact, lightweight, and easy to maintain submersible pumps from Atlas Copco.

provide all that is needed to make optimal use of the entire potential of the pump.

Reinventing and redefining repairability

Pump repairability can be inhibited by the simplest things. The use of glues or epoxy may be technically tempting to achieve a water-tight cable entry. However, from a service and repairability point of view, this makes subsequent repairs more prone to water ingress, especially when repairs are performed without necessarily having the clean environment that is required to get a suitably water-tight entry. Other submersible pump best practices, such as ‘never reuse O-rings’ are easily followed with the availability of repair kits, including all the necessary O-rings. Repair kits ensure that all necessary parts that need changing are actually changed. Otherwise, the technicians servicing the pump might find themselves forced to reuse an old O-ring, which in a submersible electric pump can lead to premature failure.

Nonetheless, repairability is more than that. Pumps that are designed with a readjustment possibility for wear, recovering performance to as-good-as-new, are desirable from a sustainability point of view. This is required as they postpone the exchange of wear parts to the absolute last moment. Repairs can be more reliably executed if essential service moments are made more secure from a service standpoint. For example, a crucial part of a submersible dewatering pump is the mechanical seal. The mechanical

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seal solves the technical challenge of making the combination of a rotating shaft, with a hole in the wall of a part, water-tight. Conventional mechanical seals consist of many parts that need to be fitted in the right order, in a relatively clean environment, which is next to impossible to find at a mining job site. Recently designed submersible pumps typically use cartridge-type mechanical seals, where the entire seal system is changed as one unit. This avoids the pitfalls of wrong assembly and contamination of critical sealing systems.

New technology in CFD, efficiency, cavitation

In hydraulic engineering, new CFD tools make predictions on potential wear-exposed hot spots more accurate. This means that in the simulation stage, already these areas can be redesigned or reinforced. Other difficult-to-predict hydraulic phenomena, such as cavitation, can today be more reliably identified and mitigated in the simulation stage, as opposed to having to rely on expensive testing and end-user trials. Using these tools, pump manufacturers that have developed new ranges of pumps after, for example, 2018 have had a completely unique chance to increase efficiency, wear-resistance, and mitigate problems related to cavitation.

Durable pumps for a longer operating lifetime

When it comes to choosing submersible pumps, it is important to pay attention to what workers in mining

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operations consider important aspects. Mostly, it will be durability (less time and effort spent on pumps that need service) and portability (inevitable mobility of pumps to clear blast areas). Often, operators will prefer the easiest plug-and-pump type of submersibles that provide incorporated start and motor protection. These are increasingly available on most higher-power pumps. Technological advances in electronics are also making built-in soft starters increasingly common, thus providing lower start currents and related start jerks when repeatedly starting electric submersible pumps. Lower stress on mechanical structures around the pump translates into longer service life.

Sustainability in focus

An important trend in all industries, including mining, is the constant search for technology that improves the environmental footprint of the operation. In that sense, electric-powered pumps have obvious advantages over diesel-powered pumps. Even more so in confined underground mining environments where exhaust fumes of internal combustion engines are a huge concern for safety. Electric submersible pumps will contribute to a better working environment; not only because they are lighter, but also, due to their electric and often submerged character, the sound pressure levels will be much lower compared to dry-installed pumps. When it comes to physical footprint, and the amount of space needed, electric submersible pumps outperform dry-installed pumping solutions when compared

like-for-like. For example, a 7.5 kW submersible pump will measure as little as 33 x 76 cm (13 x 30 in.) and weigh in at about 60 kg (135 lb). An equally powerful dry-installed pump will have both a larger footprint and weight.

Making submersible pumps future-ready

The submersible pump technological landscape had been pretty stagnant from the 1960s up to 2015. However, recent leaps in manufacturability, engineering, and the right-to-repair movement have created pumps that provide tangible advantages in the working environment and sustainability. Global pump manufacturers are often in a better position to reap the benefits of these changing environments and enjoy economic scale, and technology from adjacent products has the ability to attract the best partners in each local market.

Interesting developments lie ahead with the transition from fossil fuel to electric-powered machinery, and also the transition from traditional power generation to green power generation, in combination with battery storage systems. All of these will drive the demand for reliable, efficient, sustainable submersible pumping solutions and the world’s pump manufacturers are gearing up to meet the challenge. Designing, manufacturing, and servicing the pump of the future is no small feat, but many global brands are well on their way to delivering new and advanced next-generation pumps.

Kerryn Sakko and Grant McHenry, Rockwell Automation, Australia, discuss how machine-learning technology, and specifically model predictive control, can help mine and plant processes run closer to their constraints.

Issues such as declining ore grades and rising material costs are putting pressure on the mining industry to squeeze more out of every piece of equipment. But, the basic control strategies used with many of these assets have already been pushed to their limits, making even the smallest improvements in recovery and throughput often out of reach. Today, to take equipment performance to the next level, a more advanced form of process control is required. One solution that some in the industry are turning to is model predictive control (MPC) software. It uses machine learning and real-time data analytics to help reduce variability, and operate processes as close to their constraints as possible. While MPC has been recognised across the

industry for decades, modern applications of the technology have the potential to reduce variability, increase throughput, and save energy throughout a plant’s lifecycle.

How it works

MPC software has garnered more attention in mining and mineral processing in recent years, as companies have realised they have endured the industrial control system as far as they can take it using operator-dependent control strategies.

For a typical process, an operator can only look at an individual set point once every 15 – 30 minutes or so. As a result, their control decisions are not responsive to what is

happening live in the process. Operators can also only make decisions based on the limited set of information that is presented to them, instead of the multiple variables that exist in a process.

MPC software can monitor set points as frequently as every 30 seconds or faster, and access the many variables that a human operator is unable see. The collected data is then fed into process models that incorporate historical data, process equations, data from plant tests, and operator knowledge.

Using supervised machine-learning technology, the software can assess current and predicted operational data, compare that data to desired results, and compute and update the setpoint targets for a process. All of this is done continuously, with the goal of pushing the process to its constraints, while maintaining an appropriate margin of safety.

The software can also use unique features like virtual online analysers (VOAs), which can reduce an operator’s reliance on infrequent measurements for control decisions. Instead of waiting hours for a lab sample, for instance, a VOA can correlate lab and process data for faster and better decision-making.

Ultimately, MPC software can serve as a mine or plant’s best operator. It can run around the clock, without a break or shift change, using a volume of data that would overwhelm any human.

This is not to say that MPC software replaces human operators. They are still essential to getting a process up and running, monitoring for issues, and intervening where necessary, but, because the software handles the intensive job of monitoring and adjusting process control, it removes the more tedious aspects of an operator’s job. This enhances the role of operators, allowing them to serve more as

operations supervisors, and focus on higher-value needs in mines and plants.

MPC success stories

Mining and minerals companies around the world have used MPC software to get more from their assets.

In one case, a leading global minerals supplier turned to MPC software to improve operational consistency and stability in a complex mineral drying process at one of its sites. The company had determined that eliminating bottlenecks within the process could increase process efficiency, and allow for significant production increases.

Using real-time operating data collected from the site, MPC engineers created process models and designed an MPC control application for the drying process. The solution resulted in a 12% increase in production, a 50% decrease in process variability, and a 6%/t reduction in natural gas use.

The project exceeded the original business investment targets and prompted the company to expand the MPC application to two adjacent dryers. The company is also exploring other potential MPC projects in its other milling, drying, and calcining operations in North America and Europe.

In another case, a company used MPC software to improve the performance of the flotation unit at an iron ore mine in Latin America. Specifically, the company wanted to minimise reagent usage and maintain iron concentrate quality within specification, while reducing variability.

A key aspect of the project was the MPC VOAs. Instead of waiting for lab samples, the VOAs provided continuous process data to support faster decision making.

The MPC software led to a 30% reduction in reagent usage, resulting in about US$2.5 million in annual savings. The technology also helped the mine increase the concentrate

Figure 1. A visual demonstration of how model predictive control technology can reduce variability and help mining processes operate closer to specifications and performance limits while maintaining proper safety margins.

grade of its most valuable concentrate type from 46% to 73% on average.

Key considerations for MPC projects

For all the value that MPC software can deliver, it is worth remembering that this is a complex, multi-variable technology. To be successful, an MPC project must be well planned, implemented, and supported. Some key ingredients in every MPC project include:

A thorough assessment

MPC technology can address a wide range of needs and challenges in mines and mineral processing plants. Common pain points that companies target with the technology include:

n Failure to reach nameplate capacity.

n Inconsistent performance between shifts.

n Struggles to boost throughput and recovery.

n Process stability and quality issues.

Some companies are also turning to MPC technology to help improve resource management. They may want to better utilise water, or they may be using renewable energy sources and want to optimise their energy usage by buying and selling energy to the grid based on market prices.

Whatever issues need to be addressed, a good practice is to start an MPC project with a validation phase. This helps determine the viability of the project using engineering inputs. At least one year’s worth of historical data should be used to get a good understanding of the process, including its minerology profile and any environmental influences.

These inputs can help determine the baseline performance of the process, and outline potential targets for improvement with MPC technology. They can also help define scope, schedule, cost, implement instrumentation gap analysis, and calculate ROI for the project. All of this information can then be packaged into a technical commercial proposal document for leadership approval.

A collaborative design and deployment process

After an MPC project is approved, developing a functional specification is the next step. This process should involve the participation of all stakeholders impacted by the project. Often, that includes metallurgy team members, controls engineers, operators and operations managers, maintenance technicians, and lab staff.

Each of these stakeholders will bring crucial insights and experience, whether they are helping to build process models, define key performance indicators to measure, or test and commission the technology. But, this diverse group of stakeholders also has another important role: helping address the crucial change-management aspects of an MPC project. An MPC project creates changes that, if not properly managed, can disrupt operations or derail the project itself.

For example, operators may not be prepared for the complexities involved in MPC-based process control. They may think the software is driving a process in the wrong direction when, in fact, it is not. Or, if they do not trust the MPC software, they may over constrain it, which will diminish

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the benefits of the technology. Operators may even disable the software because they think it is doing something wrong.

Involving operators in the design phase and taking proactive steps, such as having MPC engineers sit with them during training to answer questions, can help them learn about the technology and avoid issues down the road.

Strong support

Continuous support for MPC projects helps keep them on track. For example, maintaining instrument reliability is critical. If an instrument starts failing and gives unreliable or inconsistent results, then the controller’s performance will suffer. A safeguard measure used to mitigate this risk is

to deploy a virtual sensor to compare an instrument’s actual reading against its predicted reading. Any deviations between the two can spark an investigation into the instrument. Also, any hardware changes made to the process requires corresponding changes to the predictive models. If an aging pump is replaced with a newer model with greater capacity, that change needs to be incorporated into the software to make sure its models accurately represent the process.

Enabling the mine of the future

The mining industry is evolving towards more connected, digitalised and remote operations, and MPC software has a key role to play in this shift.

Because the technology reduces the need for operators to ‘babysit’ production assets, those operators can be better utilised to support other production needs. This can help companies rethink staffing as they transition to more autonomous and remotely managed operations. Additionally, MPC software can be integrated with analytics and IoT platforms to help compare and optimise equipment performance across multiple sites.

Of course, remote and digitalised operations are only possible if current operations are profitable and can fund those initiatives. That is why MPC software has a critical, singular job to do before it helps realise any future state, and that is to help squeeze every extra percentage of additional recovery, throughput, and energy savings possible out of the current operations.

Figure 2. Mining operations technology.

Burkhard Scherf, Thiele GmbH & Co. KG, Germany, considers how improved materials and galvanising on AFC-chains can promote better endurance and test results.

GO THE DISTANCE WITH GALVANISATION

In a number of highly productive longwall coal mines, the conditions are so adverse and demanding for the equipment involved that the lifetime of standard AFC-chains is not sufficient, and thus the chains fail prematurely. By carefully selecting chain materials for their resistance against fatigue, and with hot dip galvanising, corrosion resistance can be improved considerably. The combination of both measures has led to very good results in the past, in terms of the chain lifetime, at mines with these perilous conditions.

Standard and improved material: the main features

The standard chain material is set by DIN-Standards 22255 and 17115 as: 23MnNiMoCr5-4, 1.6758. The general dependency of the standard chain steel from the tempering temperature is shown in Figure 1. While the hardness and tensile strength decreases with higher tempering temperatures (red curve, right vertical axis), the impact toughness (blue curve, left vertical axis) increases considerably with the higher tempering temperature.

The curves are the result of the testing of the raw material – with the hardening, quenching, and tempering under precise laboratory conditions. Because of the bend and weld of the round links, and the forging process for the vertical links, the fibre flow in the material and the grain sizes are influenced, and some deductions at the impact toughness must be made for the chains. The limits for chains according to DIN 22255 (and 22252) are set by the standard: minimum 57 Joule impact toughness and a hardness of 345 – 395 HBW.

Figure 2 shows the greater deviations at the impact test between four melts from four steel plants, but all melts are in accordance with the 23MnNiMoCr5-4, 1.6758. By that given characteristic of the standard material, it is not possible to increase the tensile strength for higher fatigue resistance just by choosing a lower tempering temperature. This is because the impact toughness drops under the

minimum of the DIN-Standard. Improved materials are therefore the way to achieve improved results.

One of the main features of these improved materials is a higher Molybdenum content. Secondly all other ‘beneficial alloys,’ such as manganese, chrome, and nickel are at the upper end of the DIN-Specification. Last but not least, the low content of sulfur provides the precondition for rather high impact toughness and higher hardness than standard. By these materials approximately 5 – 10% higher tensile strength is achieved, and the impact toughness values are improved. The higher tensile strength provides an over-proportional increase at the fatigue resistance.

Corrosion cracks and galvanising

Corrosion is another challenge for mining chains, especially for AFC-chains. Corrosion pitting typically creates the initiation points for corrosion cracking. Depending on the corrosiveness of the conditions at the longwall, and on the load and overload-levels, which are applied to the chain, corrosion fatigue can also occur. It is possible to differentiate between corrosion cracking and corrosion fatigue, but in both cases the corrosion should, and can, be suppressed effectively by the ‘hot dip galvanising’ of chains.

The basic principle of the galvanising is, that the zinc works as the sacrificial anode. From wear and tear the zinc layer is removed at some areas from the chain surface, but the remaining zinc – adjacent to the bare chain steel – leads the anodic/kathodic reaction, as shown in Figure 3: the zinc is dissolved, and the chain steel is protected. In the case of mining chains, the ‘hot dip galvanising’ leads to a zinc coating with a thickness of approximately 200 – 300 µm. This provides plenty of material, which works as the sacrificial anode.

Even after finishing one panel with 1.4 million t raw, approximately 50 % of the zinc layer is still present, as the laboratory examination shows at test number LA-5417, remaining thickness was 107 µm (Figure 4).

This chain at test LA-5417 was a 38 x 137 mm TIP-TZN chain, and has achieved 1780 kN at the break force test, which is equal to 98% of the requirement for a new chain (minimum 1820 kN), secondly at the fatigue test the used chain sample achieved 142 439 load cycles until break. The requirement for a new standard chain is a minimum of 70 000 cycles.

Figure 5 shows the optical appearance of a practical exercise. The two photos show a galvanised chain (left) and a non-galvanised chain (right), which have been used as AFC-chains in the same panel from the start to the end. Not only is there great variation in their optical appearance, but there are great differences in the remaining features of these chains.

Chain testing after usage/ for the remaining lifetime

At ‘routine laboratory inspections,’ where used chain samples are tested in the laboratory, great differences can be observed. These are caused by the differences of the condition at the individual faces, but also differences between chains with different specifications. In Figure 6, the test methods, and their different test results, are presented.

Test one

One test – besides the wear inspection, which is rather simple and not part of this viewing –

Figure 3. The electro-chemical principal of the zinc-protection.

Figure 2. Deviations of standard material and impact toughness.

Figure 1. Standard material – dependency of tensile strength and impact toughness.

is the so called ‘break force test.’ On the left side the test graph of laboratory test number 550 on a used 48 mm chain (non-galvanised) is shown. On the right is the graph from Test No. 576, also a 48 mm chain, but galvanised. Obviously, the galvanised chain reached not only a higher break force, but also considerably more plastic elongation at break. The amount of plastic elongation at break stands for the energy, which is absorbed during the test (in a simplified viewing, more in the following).

The used non-galvanised chain here at the test no. 550 achieved 2502 kN and 5.9 % elongation at break. The break

force equals 86% of the requirement for a new chain (2900 kN). The used galvanised chain (test number 576) reached 2706 kN and 8.1% elongation at break. Here the break force is 93% of the requirement.

One guide value for re-use is to have a minimum 90% of the break force requirement for a new chain (2610 kN in this case). The non-galvanised chain in this case is clearly below the guide value, and the galvanised chain is notably above. Indeed, the loss of break force at the non-galvanised chain is nearly twice as much as the galvanised chain.

The second factor is the amount of absorbed energy during the break force test. For re-use it should be more than 60% of the requirement for a new chain. The simplified calculation of the energy, which is absorbed through the test, is the multiplication of break force and elongation.

Here is the simplified calculation for the non-galvanised chain:

(2502 x 5.9) / (2900 x 11) = 0.463 (46.3%). And the simplified calculation for the galvanised chain is as follows: (2706 x 8.1) / (2900 x 11) = 0.687 (68.7%). The galvanised chain does not only meet the guide line for the elongation, the value is nearly 50% higher than it is for the non-galvanised chain.

Test two

The second important test point for the preventive routine laboratory check is the fatigue test. The parameters for the load cycle test are set by the DIN-Standard 22255 and 22252. The upper and lower load level, specified as 250 and 50 N/mm2 respectively, and the minimum break force is 800 N/mm2. The load levels used by this fatigue test are a good approximation of real load cycles in operation. With usually 1 Hz as a test frequency on the common fatigue test machines, it takes 19.44 hours until 70 000 load cycles are reached, which is the minimum for new chains. The upper image of Figure 7, the fatigue test sample from test report 550 (non-galvanised) can be observed, with a break at 58 010 load cycles. Meanwhile, the lower image shows the fatigue test sample from test number 576, which was stopped after 100 000 cycles without break. A new chain must be able to endure over 70 000 load cycles. For a used chain to endure anything over 100 000 cycles is rather irrelevant. With 40 000 load cycles as the recommended threshold value for re-use, both chain samples here met the guideline.

Corrosion fatigue and corrosion cracking

The examination of the corrosion is the third ‘factor’ when it comes to the laboratory examination on used chains. For example, Figure 8 shows heavy corrosion pitting on a chain (test report 2449) with a break at the break force test. The whole degree of the

Figure 5. The optical comparison of galvanised and non-galvanised chain.

Figure 6. Pulling test graph of two different chains.

Figure 4. Zinc layer, microscopic check, after completion of one longwall panel.

corrosion crack is visible. The link broke at one of the corrosion cracks – with a very low break force of 1.930 kN (required: 2900 kN).

The microscopic analysis showed the presence of several corrosion pits, one with an approximately 9 mm deep crack, and each other corrosion pit already showing signs of the initiation of cracks. Also, of some interest is the fact that the weld or weld line is visible at the right side of the cross cut. The weld line was, and is always, considered as a weak spot, but in this case the corrosion pits and cracks beside the weld are more significant. This demonstrates that weld lines today – with improved materials and ‘state of the art’ weld machines – are no longer a crucial element of mining chains.

Experience with improved materials and hot dip galvanised chains

One very recently achieved accomplishment is shown by the test LA-5417 on a TIP-TZN-chain 38 x 137 mm (used in Poland, one longwall panel with 1.4 million t), where the laboratory tests have been executed in the last days of February 2023 (just as this article is being written). The microscopic analysis – with remaining zinc after the completion of a longwall panel – and the other good test results of the laboratory examination have been mentioned.

Figure 9 shows the ‘challenge’ of standard material in another case (Australia), where premature breaks appeared in the centre of the crown. The break in the crown of the round link is one of the ‘typical break patterns’, when it comes to premature failures. The breaks had been caused by corrosion-fatigue.

These breaks happened at two ‘sister mines’ simultaneously. It is assumed that the root cause of the corrosion cracking that occurred was the nearly identical conditions at the faces of their respective longwalls. The successful solution in this scenario was the use of the improved material (TIP), in order to increase the resistance against fatigue, in combination with hot dip galvanising (TZN), which effectively has suppressed the formation of corrosion in the past.

In another case – see LA-2449, link 2.8 previously mentioned – the common failure pattern was the corrosion fatigue cracking of the round link in the leg, which typically occurs on round links where the flightbars are mounted. These ‘flightbar links’ are vulnerable to more stresses –caused by dynamics when the link with the flightbar enters the sprocket by the ‘polygon effect,’ and secondly by the lateral forces (downwards) – which are introduced from the flightbar into the link when the chain band runs through the ramps at the main and tail drive ends. Also, in this case the zinc protection suppressed the formation of corrosion pitting, in particular it suppressed the crevice corrosion in the narrow gap between the flightbar and the link. With the absence of corrosion, and the increased tensile strength of the TIP, the full runtime of the chain, without premature failures, could be achieved.

Conclusion

By combining improved material specification (Thiele-TIP) with hot dip galvanising (Thiele-TZN) in several longwall mines around the world (Australia, USA, Poland, etc.) –

each of them with very high corrosiveness and abnormal chain fatigue issues – the TIP-TZN chains have successfully solved the problems they are designed to overcome, and are used without premature failures.

Figure 8. ‘Typical chain crack’ in the leg – after the break test.

Figure 9. The second ‘typical chain crack’ in the centre of the crown.

Figure 7. Fatigue test samples of two different used chains.

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