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

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

AFRISAM ENCOURAGING APPROPRIATE BEHAVIOUR OF CEMENT CONSUMERS

With South Africa’s carbon tax in force from 1 June this year, AfriSam is providing customers with transparent pricing and the ability to make greener choices.

According to Richard Tomes, sales and marketing executive at AfriSam, the way the company complies with the new carbon tax is aimed at encouraging the appropriate behaviour of consumers. Rather than apply a blanket price increase, AfriSam is allocating the amount of carbon tax due on each bag of cement.

The carbon tax is a levy that varies according to the amount of carbon emitted in the manufacture of a product. The different cement brands in AfriSam’s range contain varying amounts of clinker – the most energy-consuming element of cement. This means that the carbon footprints of the brands differ from each other.

“We are taking a transparent and responsible approach to the new tax,” says Tomes. “By showing the amount of carbon tax payable on each specific bag of cement, our customers will still see the base price that we are charging. This avoids any confusion about how much of the final price is going toward the tax.”

He notes that this approach will also make it easier for customers to identify the AfriSam cement brands with lower carbon footprints.

“We believe that a tax should not just be a punitive tool, but it should also affect behaviour in society,” he says. “Just as cement producers are working hard to reduce carbon emissions, so the end-user can also play their part by choosing an environmentally-friendly brand.”

While certain specialist cements demand higher clinker content, he says AfriSam increasingly uses extenders to create high-quality cement brands with lower environmental impact.

Client Focus

SUCCESSFUL CONSTRUCTION OF CRESTAQUARIUM BY CONCOR BUILDINGS

The indoor CrestAquarium at Cresta Shopping Centre allows shoppers to view more than 30 species of fish. Constructed by Concor Buildings and unveiled to the public in June 2019, this ‘edu-tainment’ feature is on the lower level of the centre’s food, entertainment and cinema court.

Specialist Italian experts provided the pure cast acrylic blocks for underwater use, and Martin Muller, contracts manager at Concor Buildings explains that one of the first challenges during the project was the logistics of getting these large acrylic panels into place.

“The panels were shipped in two pieces, each measuring five metres in diameter and four metres high,” Muller says. “With each item weighing about four tonnes, they were transported in jigs and trolleyed into the confined space of the shopping centre.”

To create enough space to access the lower level, one of the shopping centres escalators was removed completely to facilitate access for the trolleys. A spider crane, positioned on the food court level above, was used to lift and position each panel. The weight exerted by the crane’s activities was considered during this operation, with back propping of the slab on which it rested being done.

Various other technicalities related to the CrestaAquarium’s operation were also attended to by Concor Buildings. This included two pump rooms and acclimatisation baths for the fish which were used before they were introduced to their new home.

“After establishing the cast concrete base for the CrestAquarium structure, we also installed service ducts for water reticulation,” Muller says. “Another important aspect was the pressurised extraction system used to prevent dust ingress.”

Concor Buildings also built insulated panels around the acrylic structure, which ensured the required heat levels allowing the panels to bond and cure over a number of weeks.

“The next phase was quite technical, with the top of the CrestAquarium being covered with a fibre-reinforced plastic cap, including stainless steel components to avoid corrosion,” says Muller. “An added consideration in almost all our work on this project was that we were working in a live environment. The centre was busy with shoppers and visitors, so it was important as always that we worked with safety as a priority.”

The final aspects of the project included the placing of custom-made, marine themed mosaics in the floor around the CrestAquarium, and hydro-testing of water pressures and equipment. Concor Buildings started on the project in August 2018 and completed it in May 2019.

Client Focus

SOUTH AFRICA SEES VALUE FROM FLSMIDTH’S NEXTSTEP INNOVATION

FLSmidth’s innovative nextSTEP™ flotation technology is proving itself in the South African mineral processing space.

According to Ricus van Reenen, Regional Product Line Manager – Separation at FLSmidth, the nextSTEP™ rotor and stator combination has been at work for over a year at a large South African platinum mine, achieving positive results.

“The customer has achieved significantly lower power consumption on the full-scale retrofits we installed early in 2018,” says van Reenen. “The more efficient design allows the same or higher slurry circulation at reduced rotor speed, leading to lower power draw.”

The retrofits have been applied to both primary and secondary flotation applications, where energy savings of over 10% have been achieved. Years of research and development have been invested in the nextSTEP™ technology, which was originally launched in 2015.

Among the key design elements are the addition of slots to the stator, adjustments in the rotor profile and a parallel distance between the rotor and stator.

“Energy dissipation is now more uniform than in traditional forced-air designs,” van Reenen says. “This means a more even wear pattern across the rotor and stator, and therefore longer intervals between maintenance.”

In the South African installations, the wear on the rotors and stators has been minimal after more than a year’s operation. In the one flotation cell, the equipment has been operational for 15 months. The thickness of the rotor has reduced from 65 mm to only 60 mm, and the stator from 75 mm to 70 mm. After 13 months of operation in the second installation, the wear is even less. The rotor’s thickness has reduced from 65 mm to 63 mm, while the stator was down from 75 mm to 73 mm.

Van Reenen highlights that there have been other benefits experienced by local users of the new technology. Among these has been 16 to 18% less blower air usage, with more concentrated bubble formation.

“Better turbulence energy dissipation around the rotor and stator region, with its related finer bubble size distribution, creates more surface area for bubble-particle attachment,” says van Reenen. “This has delivered more froth and a higher mass pull on our local units.”

The success of the nextSTEP™ technology has led to further retrofits being planned in South Africa, which is in line with FLSmidth’s drive to promote mines’ productivity and performance. Van Reenen says the intensive R&D process continues apace and is not just in the rotor and stator design but also includes areas such as smart control systems and continued digitalisation of process solutions.