Monthly Archives: September 2019

Client Focus

TRAFO SUPPLIES TRANSFORMERS FOR DATA CENTRE APPLICATION

Data centres are energy hungry beasts that operate with a high power demand, and it is important that the most appropriate transformers with the requisite protection devices are specified for this robust application.

David Claassen, managing director of Trafo Power Solutions, explains that it is important to understand data centre applications and especially the load which the transformer will be supplying as well as the type of switchgear that will be feeding it. “This,” he says, “is important from a voltage transient perspective.”

Trafo Power Solutions recently supplied two 2000 kVA 11,6kV/415V dry-type transformers to a large data centre in the Cape Town. Manufactured under stringent quality control conditions at Italian transformer OEM TMC, these specialised units are low loss transformers which conform to the European Directive EU 548-2014 and will provide greater energy savings in this application.

“Dry-type transformers are ideal for data centre applications, and correct upfront design played a role in ensuring that these transformers will meet the application requirements,” Claassen says.

The design was important in terms of the transformers windings as well as the core changes in this type of application where there is a high percentage of non-linear or harmonic load. He says that in this case the design K-factor for these transformers is 13.

These transformers were designed differently to a standard distribution load transformer and have an electrostatic shield which diverts noise to ground as well.

Trafo Power Solutions was able to assess the application requirement and provide a solution that could be delivered within a tight delivery time frame, which was an added advantage to the end-user.

Client Focus

LOCAL TECHNOLOGY AT THE CUTTING EDGE OF PROXIMITY DETECTION

With mine safety legislation getting progressively tighter, Booyco Electronics continues to ensure compliance with its proudly South African proximity detection system (PDS).

According to Pieter Janse van Rensburg, Booyco Electronics area manager for Mpumalanga, legislation coming into force in 2020 will mean the extended application of Level 9 safety standards. This level requires ‘full intervention’ from a PDS on trackless mining machines (TMMs) to avoid man and machine related incidents.

Booyco Electronics’ PDS can facilitate such collision avoidance, with automatic slow-down and even safe-stop of mining machines.

The system uses VLF antennae on a vehicle to create fields within a danger zone around the vehicle. The size of each field can be determined by the customer, to suit their specific operating environment and addressing identified risk.

An RFID tag installed on the pedestrian’s cap lamp alerts them – through a light and sound alarm – when they enter this zone. The light changes colour from green to orange and then red, the closer the pedestrian is to the vehicle.

The vehicle itself also receives a warning from the PDS, with the operator being alerted that a pedestrian is in the proximity. If equipped and configured appropriately, the vehicle can also be automatically slowed down at a certain distance from the pedestrian, and similarly brought to a safe stop.

One of the most significant advantages of the Booyco Electronics PDS is that it can effectively detect as many as seven TMMs and 20 pedestrians within one field, in the underground environment.

“Our technology prioritises the safety of the pedestrian in mines, whether underground or opencast,” says Janse van Rensburg. “Our mission is to save lives, and to ensure that every worker returns home safely every day.”

The company’s market leading systems are intrinsically safe, working on a clean 12 Volt power supply that will not ignite methane gas or coal dust. Customers value the complete turnkey solution that Booyco Electronics can provide, says Janse van Rensburg.

“Our combined technology includes a very low frequency (VLF) signal that penetrates rock walls underground,” he says. “This ensures that the pedestrian will still be warned of an approaching vehicle even if it is out of sight around a corner.”

The PDS can be applied to older ‘non-intelligent’ machines on a mine as well as the newer, controller area network (CAN) bus enabled models.

“Our data logging capacity is able to capture all information relating to the interactions between the pedestrians and the vehicles, and also between vehicles themselves,” he says. “This provides the mine with a ‘road map’ to track how any incident occurs, making it easier to report and to improve practices.”

The Booyco Electronics Asset Management System (BEAMS) gives mines the ability to extract useful data on risk areas. This can feed into focused training of staff for more effective safety behaviour.

With 13 years of experience in PDS, Booyco Electronics has supplied in excess of 5 000 sets of mining vehicle equipment around southern Africa, as well as 50 000 pedestrian sets of equipment.

Client Focus

HIGH-HEAD DEWATERING SAVES THE DAY AT LESOTHO MINE

Normal mining operations continue at a Lesotho mine, thanks to the quick delivery by Integrated Pump Rental of a rapid dewatering solution.

A constant flow of water into the mine’s pit area demanded that water be urgently and reliably pumped out. A fuel-efficient Sykes Xtra High Head pump set was chosen for the job, pumping into a 200 mm HDPE line with a head of 127 metres to a holding dam. According to Integrated Pump Rental’s Andre Strydom, time was of the essence to the customer.

“We secured this dewatering contract due to our quick and effective response,” Strydom says. “The Sykes XH150 unit was on site and commissioned just 24 hours after receiving the call from the customer.”

There was also a long term relationship with the customer, who was confident of the dewatering rental equipment available in the fleet. Strydom highlights that as mines and quarries become deeper conditions require a solution like the Sykes XH150. With its automatic priming and solids handling capacity, it is designed to dewater more efficiently and effectively.

“The unit has one of the best shaft stiffness ratios of any automatic priming pump on the market,” he says. “Sykes engineers have ensured that the enormous pressures and heads associated with such performance do not compromise seal integrity through shaft flexing.”

All models have the ability to operate unattended at high discharge heads. The pumps can be primed with long suction hoses and can manage suction lifts of up to nine metres. The units can even run dry for extended periods due to the oil bath mechanical seal assembly. Designed for robust and reliable performance with high volumes of water, Sykes pumps have an established reputation for the fast and effective control and removal of sub-surface water.

The pumps can even operate in ‘snore’ condition, which accommodates fluctuating suction levels. In these conditions, the pump will snore until the liquid is available for the pump to fully re-prime itself automatically.

“Our service levels and experience made the whole operation smooth and effortless,” Strydom says. “We strive to provide that ‘extra mile’ that a customer is looking for.”

Client Focus

CONCOR ON TOP OF STYLISH NEW FWJK ILLOVO DEVELOPMENT

The elegant Illovo Central mixed-use block near Sandton being constructed by Concor Buildings has topped out at 15 floors and is due for completion in March next year.

In a format driven by developers FWJK and increasingly popular in South Africa’s urban designs, the building will be a combination of office space and residential units. With parking taking up levels 1 to 5, there will be offices on floors 6 to 8 and apartments from floors 9 to 15. The living units are a combination of sizes including 80 studio apartments, 36 one-bedroom units, 43 two-bedroom units and 12 three-bedroom penthouse apartments.

Bulk earthworks began in May 2018, when 27,800 m3 of spoil was removed for the first three levels. According to Concor Buildings contract manager Fanie Stadler, this phase required the removal of considerable quantities of rock. In the southern corner of the property, the rock layers almost protruded at ground level.

Given the close proximity to other buildings in this well-developed suburb, Concor Buildings conducted smaller, controlled blasts to ensure the highest levels of safety. The planning and monitoring of these blasts also considered a Gautrain servitude tunnel below, and a school across the road.

“Dust control was also a key issue, which we implemented and monitored closely in line with our stringent health and safety standards,” Stadler says.

The concrete structure has been built around a lift core for four passenger lifts and a fireman’s lift. Two tower cranes have been a feature of the skyline on this project, improving efficiencies on a site that is severely space-constrained. One tower crane with its 60 m jib has focused its lifting on horizontal decking, while the other with 55 m jib provided additional hoisting for column and the shaft core formwork and concrete.

An interesting innovation that Concor Buildings has applied in constructing inner walls has been the use of Everite Hebel autoclaved aerated concrete (AAC) blocks. This lightweight building block has a number of benefits for modern buildings, Stadler says.

“The lighter load on the concrete slabs means that these slabs can be designed slightly thinner and with less reinforcing bar,” he says. While a typical brick and mortar wall is about 350 kg/m2, an AAC block wall load is closer to 90 kg/m2.

The uniform surface of an AAC wall also allows for a thinner skim coat finish, rather than the usual 12 mm of mortar required for a normal brick wall. This has positive material and logistical implications as less water, sand and cement need to be transported to and around the site. There is also mixing of mortar on site which makes for a generally cleaner site, with less dust.

Stadler highlights that the inclusion of AAC blocks has allowed Concor Buildings to demonstrate its building expertise and precision, while also further developing the skills of its subcontractors.

“With the benefits of these lightweight blocks come the demands of accuracy and attention to detail,” he says. “Added skill is required in the block laying, as well as in the plastering.”

As part of Concor Buildings’ development programme, the company worked with the block supplier to train and mentor subcontractors in working smarter and enhancing their skill levels with new techniques. This delivered the exact tolerances demanded to closely match the building’s structure with the blockwork and the glazing.

The performance glass on the outside of the building is low-e, reflecting long-wave infrared energy to keep the inside of the building cool and reduce load on the air conditioning system. A Marmoran wall coating is applied as a protective and aesthetic layer.

As with many developments in dense suburban areas, space to work has been at a premium at Illovo Central. The site office has even had to move into the building itself.

The project’s location on Rivonia Road has demanded meticulous coordination of materials delivery by Concor Buildings, while council bylaws have meant no overtime can be worked in the suburb. The construction team has therefore had to maintain tight working efficiencies to keep the project on track.

Client Focus

BUILDING A POSITIVE AFRICAN FUTURE FOR 85 YEARS

With evidence of the longevity and potential of its products on display in infrastructure across southern Africa, AfriSam’s presence is widespread.

Notably with a legacy that goes back 85 years, this leading construction materials supplier has contributed to many iconic projects. These include the Carlton Centre in the Johannesburg CBD, the Nelson Mandela Bridge, the Lesotho Highlands Water Project, numerous new developments in Sandton (including the tallest building on the continent, The Leonardo) and the Zeitz MOCAA in the V&A Waterfront in Cape Town.

Although the company has undergone changes in shareholding and names during its 85 year existence, AfriSam has remained true to its formula according to Rob Wessels acting chief executive officer and Richard Times, sales and marketing executive.

This, they concur, has been pivotal to AfriSam’s success, despite economic cycles experienced by the construction industry. The past five to six years have been particularly difficult for the construction industry (a key customer segment for AfriSam) and companies operating in the construction sector.

Wessels says AfriSam has had to “right-size the business” and adapt where necessary to remain competitive as well as continue to be the supplier of choice.

“Business performance in tough times comes through shifting and broadening our customer base, and by continuing to focus on the quality of our product, technical advice and the relationships we have with our customers,” he says.

“AfriSam has a reputation for providing quality product and expertise, and getting things right, and we’re determined to maintain this.”

Among the initiatives AfriSam undertakes to promote quality within the industry is its anchor sponsor of the Concrete Society of Southern Africa’s Fulton Awards. This, Tomes says, is in line with the company’s mission of “creating concrete possibilities by pushing the boundaries of concrete products, both in terms of sustainability and technical performance”.

AfriSam is also the co-founder of the AfriSam-SAIA Award for Sustainable Architecture + Innovation, which recognise the importance of ‘green’ building and acknowledges the contributions made by forward-thinking industry players towards brining sustainable innovation to human living environments.

Client Focus

ALL GO FOR VXP MILLS AT KIBALI

An ultra-fine grinding (UFG) circuit of eight FLSmidth VXP mills has been successfully optimised at the Barrick-operated Kibali gold mine in the Democratic Republic of Congo.

The first four VXP mills were installed in the Kibali gold recovery plant in 2014. Four additional units were added in 2017, in line with changing from dual oxide-sulphide to a full twin-sulphide operation. The decision to install additional mills was also based on the mill performance and the operator’s satisfaction with the original units. This enabled the operator to handle increased concentrate throughput from 1,500 to 2,700 tonnes per day.

According to Thamsanqa Mahlangu, Kibali’s projects metallurgist, the UFG mills are a key element of the integrated gold processing circuit. This process includes primary and secondary crushing, primary milling, flotation, ultra-fine grinding, pre-oxidation, intensive cyanide leach, carbon adsorption and elution.

“The addition of the latest four VXP mills was to handle a higher concentrate throughput from converting to twin sulphides,” Mahlangu says. “We conducted extensive test work in collaboration with FLSmidth to optimise VXP performance, to achieve our design recoveries and reduce concentrate leach residues.”

Among the factors addressed by the new configuration was the ability to handle ore variability from different satellite pits, including high iron-stone content in the Mengu ore, he says. This demonstrated the need for additional grinding capacity.

Craig Brickhill, FLSmidth’s Regional Product Line Manager – Comminution, emphasises that VXP mills operate at a power intensity that is higher than low-speed mills, and overlaps that of high-speed mills.

“This allows the VXP mill to be customised to a wide range of grinding applications,” he says. “Lower ore grades and complex minerology are driving demand for more efficient fine grinding. Typically, slurry enters the circuit at 40 to 70 microns in size, and leaves at about 15 to-20 microns, 80% passing values for both.”

Mahlangu explains that the optimisation testwork to evaluate the mills’ performance looked at key parameters such as media filling, feed slurry flowrate, mill speed and grinding assembly configuration. He agrees that it is very profitable to grind as fine as possible, but explains the importance of understanding relationships between grind and recovery, and media wear and disc wear. The latter ensures that the additional revenues to cost ratios are optimised.

Changes to the grinding assembly, for instance, included a move from standard spacing to single spacing of the grinding discs. “There are potential benefits to a single spaced design at higher media fill levels,” Brickhill says. “Power utilisation is improved, due to higher grinding assembly contact with the media mass. Also, there is an increase in the media agitation within the mill due to uniform distribution of the discs in the chamber.”

The result of adding another four VXP mills – and the optimisation process – has been very positive, according to Gustav du Toit, Kibali’s general manager.

“This has been a constructive process of fine-tuning our process for the best possible results,” says du Toit. “Working in close collaboration with FLSmidth has allowed us to find the solutions we were looking for.”

Brickhill highlights that FLSmidth customises its VXP mills to each unique mining application, optimising the performance of the mill and increasing ore recoveries.

“Through FLSmidth’s partnership approach with Kibali, our project team was able to deliver these mills within short lead times to allow Kibali to handle the higher concentrate tonnage reliably and efficiently.” he concludes.

Client Focus

EXXARO’S BELFAST MINE GETS CONCOR EXPERTISE

Concor Infrastructure is building dams, roads, platforms and other works at Exxaro’s new digital coal mine near Belfast in Mpumalanga province.

At work since October 2017, Concor Infrastructure is constructing four major dams, 26 concrete platforms and terraces, 37 internal roads of 16 km in length, and the upgrade of almost 13 km of provincial roads, among other aspects of the mine.

According to Concor Infrastructure contracts manager Pierre van Vuuren, dams are being lined with both a geosynthetic clay liner (GCL) and high density polyethylene (HDP) sheets, in compliance with the water use licence and related environmental regulations. Various structures around the dams are also being installed, including large silt traps, drying beds, inflow chutes to prevent scouring, and spillways and sumps.

Among the concrete platforms and terraces are two primary crusher bases being built for the run-of-mine crushing facilities. The various structures being built by Concor Infrastructure on the mine will demand almost 350 tonnes of steel reinforcing, and nearly 2,700 tonnes of bulk cement. Other inputs will be around 15,000 tonnes of 19 mm aggregate and nearly 13,000 tonnes of crusher sand.

Dams are lined in compliance with environmental regulations and best practice.

Extensive upgrading is being done on the D1770 and D1110 provincial roads – for the transport of coal to the rail siding – including eight major culverts under the roadway. For all the project’s road works, almost 9,5 km of subsoil drains is to be installed, as well as 2,7 km of stormwater culverts. G5 and G6 construction material comes from an external quarry and crushing plant located about 30 km from site towards Carolina.

Contracts manager Mabandla Dlamini highlights the substantial local impact of the project, including the accommodation of a core labour complement of about 180 personnel in the Emakhazeni municipal district. The overall workforce managed by Concor Infrastructure, with contractors, totals closer to 700 – who are all transported 30 km daily by the local taxi network.

Dlamini also points out that various subcontracts are outsourced to local small enterprises, such as drainage, stone pitching, paving, kerbing, fencing, security services and catering. Diesel is also sourced from a local fuel depot in Belfast; the project is expected to consume about 4,3 million litres of diesel in site-wide applications.

Over 150 items of plant and equipment are active on the site, says site agent Sarel van der Berg, with about 40 items such as articulated dump trucks, tippers and graders from local plant hirers.

Client Focus

AFRISAM CONTINUES TO FOCUS ON CARBON EMISSION REDUCTION

It is not business as usual for AfriSam, who has been working hard towards reducing its impact on the environment for many years. Since 1990, this leading supplier of construction materials has reduced its C02 emissions by 35%. But this, according to Hannes Meyer, cementitious executive at AfriSam, is not where it ends.

Speaking at a presentation to media at its Dudfield cement plant near Lichtenburg in the North-West province, Meyer said AfriSam continues to cut the carbon footprint of its cement. Efforts focus on using less energy in the production of clinker, while making more use of extenders like fly-ash and slag.

“We are probably South Africa’s leading company in our understanding and application of extenders in cement,” he said. He emphasised that this field holds great scope for creating more environmentally friendly cements, but required considerable technical expertise. With its many years of experience, AfriSam was applying that expertise in its ongoing cement innovation.

Limestone mining at Dudfield began in 1949, with the first kiln established in 1965. Today, the plant produces over a million tons of clinker on its Kiln 3 plant to meet market demands. The plant has a cement production capacity of over 1.3 million tons. The plant also has the flexibility to supply bulk cement by both road and rail, as well as its own bagged cement. There are 65 years of proven limestone reserves on AfriSam Dudfield’s 3,608 ha mining licence.

AfriSam invests constantly in energy saving strategies at its cement plants. Since 1990, it has achieved a cumulative reduction of 31% of cement-specific thermal consumption, measured in megajoules per tonne of cement.

Meyer highlighted the potential of the new carbon tax – in force from 1 June 2019 – to incentivise energy-saving innovation.

“The depressed state of the economy has dampened many of industry’s good ideas, and if carbon tax revenues could cover industry incentives, the resulting innovations would have a range of positive spin-offs. Apart from easing demand on Eskom’s grid, this would also contribute toward the country’s Paris Agreement obligations,” Meyer said.

AfriSam’s commitment was clear to see, he said, being the country’s first cement manufacturer to equip all its kilns with bag filters. This brought emissions to below even the European standard of 30 mg/m3.

Client Focus

USING QUALITY MOTORS AND GEARBOXES OPTIMISES SCREEN ECONOMY

Harsh operating conditions on vibrating screens demand high quality engineering and the strictest tolerances for unbalanced motors and gearboxes, or they simply do not last.

According to Kenny Mayhew-Ridgers, chief operating officer at Kwatani, local design and manufacture to the highest standard is therefore a non-negotiable. The company designs its own range of motors and locally manufactures the gearboxes for its vibrating screens.

“We design our own motors with local conditions in mind, giving the customer a high performance and long lasting product,” says Mayhew-Ridgers.

This includes optimal sealing arrangements for keeping electrical components dry and clean. Power cables, for instance, must always enter from the underside to prevent water ingress. The design must consider various orientations of the motor, depending on the angle of installation. Dusty conditions on mines also present a challenge.

“Dust ingress can compromise the sealing configuration of the lid,” he says. “Our design is therefore like a top-hat, so the O-ring is not on a flat surface but rather on a cylindrical, vertical surface. There is even a double-sealing arrangement for the lid, which includes a gasket.”

Kwatani’s gearboxes are fully locally manufactured, with only the high quality bearings imported direct from leading global producers. Gearboxes comprise two shafts, each with its own set of unbalanced weights linked to each other by a gear to achieve synchronised motion. Gears and shafts are locally fabricated by selected suppliers, while the housing is cast by a local foundry and machined to exacting specifications.

“We have spent a great deal of effort on the sealing configuration, to ensure no oil leaks,” he says.

He notes that Kwatani is probably the only OEM that services its own gearboxes. This ensures adherence to strict tolerances, so that units have sustained performance and longevity.

He also highlights the massive centripetal forces that are exerted on the screening machine by the unbalanced motor and gearbox. This make it vital to secure them well to the screen.

“To achieve this, we specify our own fabricated bolts, nuts and washers,” he says. “If sub-standard fasteners are used, components can come loose and cause extensive damage.”

Unbalanced motors usually have to be installed at an angle. Taking account of the weight of these components, there are rigging points all around the housing to manipulate the angle of installation. The feet are normally larger than those of competitors, for a better contact surface.

“If there is the slightest imperfection in the flat surface of the join, this can cause costly damage to the drive and the screen,” says Mayhew-Ridgers. “This is why OEMs like Kwatani have such detailed installation procedures on issues like torqueing of bolts. Installers and maintenance teams need to stick closely to these specifications.”

Client Focus

UNDERSTANDING DESIGN CHOICES FOR VIBRATING SCREENS

Don’t generalise about the advantages and disadvantages of different vibrating screen technologies, advises Kwatani CEO Kim Schoepflin; the key consideration is the application.

“When a customer considers their options for a screening machine, there are a number of good technologies from which to choose,” Schoepflin says. “The appropriate technology choice will depend on the application, and we believe there is a space for every technology.”

Brute force screening is the most common technology employed among mining screens. Its benefits include being generally cost effective, relatively simple to maintain and economic in terms of life cycle costs, all of which translate into lower Total Cost of Ownership (TCO).

“Having the mechanical and metallurgical knowledge in-house, Kwatani can provide the technology that best suits the application,” she says. “We are not tied to one technology, and our primary focus is on understanding exactly what the customer needs, and providing a solution that is engineered for tonnage.”

Twin-mass or resonant screens, which run very close to a natural frequency, have a self-amplification benefit, says Kenny Mayhew-Ridgers, Kwatani’s chief operating officer.

“This gives the screen a greater energy-efficiency,” he says. “There are, however, limits on the size of these units. In addition, maintenance is more costly as springs or rubbers must be changed regularly or the efficiency benefit is lost.”

He notes that twin-mass screens also tend to be heavier. This can cause confusion when presenting technology comparisons to customers.

“Often the overall mass of the twin-mass screen is compared with the mass of the brute force screen, and this is obviously not correct,” he says. “Rather, it is the deck sizes that must be compared, as this is the element that does the work.”

While the mechanics that drive the screening process is different, the motion of the panel is what is important. This is where interaction occurs between the particles and the screen panels. The efficiency of the process then depends on the screen’s speed, frequency, drive angle and movement of the panel relative to the particles.

While some proponents will generalise about common challenges with brute force screens, Mayhew-Ridgers notes that these observations are seldom valid. Various manufacturers offer a range of brute force technology solutions, each with its own benefits.

Schoepflin highlights that Kwatani works to raise awareness in the industry about what each technology is about. This makes it easier for users to make informed decisions about the technologies they choose. She also says it is important for users to be confident that their chosen screen is well supported by local experts.

“It is vital for OEMs to prioritise the customer’s application when considering the basic screen technology and design,” she concludes. “While optimising screen panels to achieve higher screening efficiency is always an option, it is not the silver bullet.”