Monthly Archives: June 2023

Client Focus

ZIMPLATS SEES SIGNIFICANT DUST REDUCTION AND INCREASED PRODUCTIVITY WITH WEBA CHUTE SYSTEMS

Custom engineered chute systems have significantly reduced dust levels while increasing productivity at Zimplats. Over the last two decades, Weba Chute Systems has installed 99 of its tailormade transfer points in various applications across the mine and processing plants.

Showing a rendered image of the transfer chute at the conveyor underground decline conveyor.
Showing a rendered image of the transfer chute at the conveyor underground decline conveyor.
Showing a rendered image of the crushing discharge transfer chute.
Showing a rendered image of the crushing discharge transfer chute.
Showing a rendered image of the crushing station vibrating primary jaw crusher transfer chute.
Showing a rendered image of the crushing station vibrating primary jaw crusher transfer chute.
Showing a rendered image of the crushing station vibrating grizzly transfer chute.
Showing a rendered image of the crushing station vibrating grizzly transfer chute.

These bespoke installations span various applications including conveyor onto conveyor transfer chutes, apron feeder discharge chutes, mill feed chutes, conveyor onto bins transfer chutes, screen over and under size chutes, silo chutes, and transfer chutes at the crushing and screening stations.

Weba Chute Systems recently secured another contract to provide ten custom-engineered transfer chutes for the expansion of an underground crusher station at Zimplats.

Izak Potgieter, Systems Manager at Weba Chute Systems.
Izak Potgieter, Systems Manager at Weba Chute Systems.
Ted Cruickshank, Project Manager at Weba Chute Systems.
Ted Cruickshank, Project Manager at Weba Chute Systems.

Ted Cruikshank, Weba Chute Systems’ Project Manager, explains that these chutes will handle the transportation of run-of-mine material from the ore pass to the underground crusher and from the crusher to the outgoing conveyor. He says the engineering and construction of these chutes will ensure a fit-for-purpose robust solution with the height of the chutes ranging from two to six metres.

Sharing specifics, Cruikshank say that the chutes before the crusher are designed to manage large material up to 650 mm in size from a vibrating feeder, with a maximum tonnage of 1,100 tph. “Other chutes will transport the feeder’s undersize, less than 180mm in size, at 550 tph, while still others will be employed in conveyor-to-conveyor applications, feeding 1,500mm wide belts with up to 1,350 tph of material and a maximum lump size of 250mm.”

Weba Chute Systems’ unique chute design philosophy, based on the cascade system, extends the wear life of the chute through the strategic placement of dead boxes, creating a layer of ore for the moving material to flow over. Replaceable lips are incorporated on the dead boxes facilitating easy and quick swap out at the necessary intervals. Easily accessible inspection doors are also a feature which will ensure maintenance becomes an effortless process.

Cruikshank says that this design has proven particularly effective at Zimplats due to the abrasiveness of platinum ore, and the Weba chutes will continue to ensure the smooth, controlled flow of mined and crushed material, leading to less wear, damage and spillage on conveyor belts and a marked reduction in dust.

Weba Chute Systems’ innovative design has been particularly effective in reducing dust levels. Izak Potgieter, Systems Manager at Weba Chute Systems ,cites the example of the bunker discharge chutes.

“In this application considerable dust levels were created due to material of up to 500 mm in size moving through the conventional transfer point at a rate of 600 tph with no control of the material result in an uneven flow creating a lot of energy for dust particle to expand into the surrounding atmosphere.”

Following the replacement of the conventional transfer point with a custom engineered Weba chute dust levels were considerably reduced by about 40% and Potgieter explains that by controlling the velocity of the material it is not only possible to reduce dust generation but also to improve flow control reducing impact and wear which in turn minimises maintenance downtime.

Hilmax, Weba Chute Systems’ local agent in Zimbabwe, will oversee the chute installations and provide spare sets of wearing lip liners for each chute to ensure optimal uptime for Zimplats.

Client Focus

TREND IS TOWARD LARGER  POWER PLANT SOLUTIONS, SAYS ZEST WEG

Whether companies need power to survive loadshedding or to raise their production output, the trend is for these power generating systems to get bigger.

Bernard Mitton, Business Development Consultant at Zest WEG.
Bernard Mitton, Business Development Consultant at Zest WEG.

According to Bernard Mitton, Business Development Consultant at Zest WEG, it is becoming more common for customers to request proposals for power solutions that exceed 10 MW. In South Africa, this appears to be mainly a response to rising levels of loadshedding. In other parts of Africa, says Mitton, it is economic growth that drives demand.

“For many companies who want to grow their output, it is vital to have continuous and reliable power supply,” he says. “In recent years, Zest WEG has been designing and installing more of these large power plants for customers across Africa.”

It is Zest WEG’s depth of in-house engineering expertise and technical capability that earns it these contracts, he explains. From the generator sets themselves to the transformers, switchgear and containers, the company can provide customers with a full turnkey solution.

Generator installed in a 40ft high cube container.
Generator installed in a 40ft high cube container.

“We often propose a modular system that allows the customer to execute their project in phases,” he says. “They can begin with the most cost effective solution, and then expand the plant as the power demand grows.”

In one of these 10 MW systems, there will usually be eight to 10 generators installed within a containerised solution or a dedicated power plant room. They can generate power at 400 V, to be stepped up by transformer up to 11 kV – or power can be generated directly with an alternator output up to 11 kV.

“For a typical 10 MW power plant, we connect the generators to a common switchboard up to maximum 22 kV, to distribute power to the various on-site loads,” he says. “The switchboard solution can be installed in a container, an E-house or a plant room.”

The generating units are custom engineered, built and fully tested in Zest WEG’s Cape Town generator facility. Testing includes a step load test and the synchronisation of generators to each other –  verifying all setpoints, engine performance and efficiency indicators.

Client Focus

DRILLING EXCELLENCE PAVES WAY FOR IVANPLATS’ PLATREEF PROJECT VENT SHAFT

The dual purpose use of the new ventilation shaft at Ivanplats’ Platreef Project near Mokopane required extreme pilot hole accuracy – so it called in specialist Murray & Roberts Cementation.

The vent shaft, which meets horizontal development at a depth of 950 m, also needs to be equipped with a hoist and rope guides to carry personnel in the case of emergency. The rope guides for the hoist require the shaft to be drilled vertically within tight parameters. According to Dirk Visser, Senior Project Manager at Murray & Roberts Cementation, this meant offering the client minimal deflection of the pilot hole using a continuous steering tool.

At the completion of the hole at over 950 m depth, the actual results showed that the drilling team were not more than 0,05% off on their closure distance.
At the completion of the hole at over 950 m depth, the actual results showed that the drilling team were not more than 0,05% off on their closure distance.
In one of the most accurate pilot holes to be drilled on a South African mine, Murray & Roberts Cementation recently completed a 950 m borehole for a ventilation shaft at Ivanplats’ Platreef Project.
In one of the most accurate pilot holes to be drilled on a South African mine, Murray & Roberts Cementation recently completed a 950 m borehole for a ventilation shaft at Ivanplats’ Platreef Project.

“Using the well-proven German designed and manufactured Micon, Rotary Vertical Drilling System (RVDS), we were able to achieve the set parameters required for a rope guide installation,” says Visser. “The worst deflection was no more than 0,05% – or 452 mm – and by the time we bottomed out, the deviation was only 0,02% or 226 mm off centre over a final drilling depth of 950 m.”

He highlights that Murray & Roberts Cementation has an established reputation for achieving high levels of accuracy in directional drilling.

Micon’s specialised RVDS is a continuous self-steering tool working on a close loop system which steers the tool using two-axis gyro inclination sensors which activate the hydraulic steering system. It can determine in real time if there is any deviation from the vertical course, and communicate this information to the operator on surface via pressure waves in the drilling water by converting the pressure waves into information through transducers.

The Murray & Roberts Cementation drilling team not only ensured accurate directional results, but also optimised the performance of the RVDS. By keeping an eye on key variables like voltage levels and water cleanliness.

He highlights that drilling to these tolerances with this highly technical equipment demands a very experienced team. On this project, for instance, the most ‘junior’ person has worked with the RVDS for 15 years, while another member has 28 years of experience in raiseboring.

Client Focus

SEW-EURODRIVE LAUNCHES X.e AGITATOR GEAR UNIT

Building on the success of its tried-and-tested X.e series of high-performance industrial gear units and gearmotors, SEW-EURODRIVE has launched a new X.e series agitator gear design.

SEW-EURODRIVE’s new X.e agitator drive provides reliable and efficient operation when handling the strongest loads.
SEW-EURODRIVE’s new X.e agitator drive provides reliable and efficient operation when handling the strongest loads.

This agitator gear unit boasts high permissible forces and bending moments alongside its operational reliability – making it ideal for all high-performance agitators and mixers. According to SEW-EURODRIVE’s Head of Business Development Engineering, Andreas Meid, the agitator gear design expands the company’s portfolio to include more application gear units designed for specific uses.

“Agitator gear units are used in various industries across Africa including chemical, pharmaceutical, food and beverage, and water and wastewater treatment – for mixing and blending liquids and other materials,” says Meid. “The X.e-series agitator gear units can be used wherever high power ratings are required for stirring and mixing liquid or paste-type materials.”

Leading global supplier of drive technology SEW-EURODRIVE has released an agitator gear unit in its tried-and-tested X.e series.
Leading global supplier of drive technology SEW-EURODRIVE has released an agitator gear unit in its tried-and-tested X.e series.

SEW-EURODRIVE’s X.e series features a modular design for flexible customisation, and includes innovative motor and gear unit technology that ensures high efficiency and long service life. As part of this range, the SEW-EURODRIVE X.e agitator gear unit is designed to provide reliable and efficient operation in these demanding applications.

Meid highlights that the ‘digital twin’ concept was applied throughout the design process for the X.e-series agitator gear unit, making it possible to simulate and optimise the mechanical components and oil flow in virtual reality.

“The application-specific rolling bearing concept – with a large bearing spacing and its rigidity optimised agitator housing – allows the unit to absorb the strong forces and bending moments that typically occur in agitation and mixing processes,” he explains. “Depending on the particular load scenario, there are three load-specific rolling bearing variants available for each size.”

The X.e-series agitator gear units can be used wherever high power ratings are required for stirring and mixing liquid or paste-type materials.
The X.e-series agitator gear units can be used wherever high power ratings are required for stirring and mixing liquid or paste-type materials.

The X.e agitator gear unit’s advanced gear technology, which includes helical and bevel-helical gearing, provides high torque transmission with low noise and vibration. This ensures smooth and efficient operation, even in high load applications.

“Among the innovative design elements of the gear unit is an oil expansion chamber to compensate for temperature variations,” he says. “It also features a labyrinth sealing system to prevent contamination and reduce the risk of oil leakage.”

The units are available in three sizes, for a torque range of 117 to 217 kNm. As a three-stage or four-stage helical gear unit, it also covers gear ratios ranging from 20 to 400.

Client Focus

NUMBERS THAT MATTER DON’T APPEAR ON ANY SALES QUOTES, ARGUES PILOT CRUSHTEC

While the quotation for an item of equipment reflects its upfront price, it says nothing about the history, experience, product quality and service infrastructure required to sustain optimal production levels for the customer.

“Sustainable and reliable production is at the heart of any crushing operation, and this is what customers are really paying for when they purchase capital equipment,” says Francois Marais, Sales and Marketing Director at Pilot Crushtec. “For this reason, the numbers that matter are those that reflect a supply partner’s ability to help customers meet their vital deliverables.”

Marais highlights that Pilot Crushtec has spent 33 years building a reputation for its quality of product and its outstanding service levels. Its engineering prowess has already seen over 300 Pilot Crushtec modular plants placed into operation with customers, with over 2,000 mobile crushers, screens and conveyors sold and commissioned.

“Other numbers that matter include the 170 modular cone crushers and the 200 modular jaw crushers that we have sold into the market,” he explains. “We estimate that our equipment has to date processed about 5 billion tonnes of material – in around 1,000 different applications and processes.”

Pilot Crushtec runs a 24/7 operation and has over 15 dedicated support technicians available to ensure your plant and operation has minimum downtown.
Pilot Crushtec runs a 24/7 operation and has over 15 dedicated support technicians available to ensure your plant and operation has minimum downtown.
On average, 6788 parts are dispatched monthly from Pilot Crushtec’s 12,000m² facility based in Jet Park, Boksburg.
On average, 6788 parts are dispatched monthly from Pilot Crushtec’s 12,000m² facility based in Jet Park, Boksburg.

He notes that, all too often, equipment purchases are made purely based on capital pricing. Down the line, he says, it may be realised that the necessary technical assistance, experience or parts are not readily available to support the equipment. Pilot Crushtec has made a strategic philosophy of its customer commitment, by investing heavily and continuously in service infrastructure, spares and wear parts and continuous training of its people. 

“For instance, we train, develop and retain the skills necessary to keep customers’ equipment up and running – to avoid costly downtime that could threaten their contracts and reputations,” he says. “This includes our 15 full time service technicians, who travel a million kilometres a year to see customers and deliver quality support.”

Underpinning these superior levels of service – which are available 24/7 365 days a year – is the company’s parts and aftermarket infrastructure, which is similarly always open for business. This starts with a large stockholding of around 93,000 items, including about 2,500 wear parts alone. There are 20 dedicated parts personnel to efficiently manage this valuable resource, dispatching 6,788 parts on average every month.

“These numbers reflect the real value that we deliver to our customers and should be fundamental factors taken into account when any quotations are considered,” says Marais. “While the procurement function for equipment is often incentivised to save a little money upfront in a capital purchase, this can create unintended consequences for buyers when production is jeopardised.”

Client Focus

SUPPORTING CONTRACTORS’ GREEN AMBITIONS

With the trend towards green buildings, contractors are expected to support their customers in reaching sustainability goals; AfriSam’s product range has been evolving with this front of mind.

Decades of innovation in terms of environmental responsibility and carbon reduction have put AfriSam out front, according to Hannes Meyer, Cementitious Executive at AfriSam. The company was one of the first to develop its own sustainability road map, and this is now paying off for customers.

“The sustainability drive in the construction sector is gathering momentum,” says Meyer “The carbon footprint of construction materials is where contractors can make immediate gains when looking to align a project with more stringent environmental standards.”

The company’s manufacturing processes are among the most energy efficient in the sector.
The company’s manufacturing processes are among the most energy efficient in the sector.

Meyer points out that the company has made continuous progress in fields such as energy efficiency, cement extenders, water conservation and biodiversity. This allows customers to procure products in the knowledge that the environmental and carbon impact is minimised. 

“We give our customers the opportunity to support a more sustainable future for the sector by choosing construction materials that embody this commitment,” Meyer explains. “We do not just set theoretical targets for environmental performance; we are practical about what we can achieve, because we have been innovating on this front for so long.”

This is in clear contrast to a significant level of ‘green-washing’ in this sector, where many companies advertise a sustainable approach but without credible evidence of how their targets are to be achieved. Since 1990, AfriSam has been able to reduce the volume of carbon dioxide emissions per ton of cementitious material by 33%.

In a carbon-intensive industry like cement manufacturing, it is difficult to reduce the carbon impact without a depth of expertise and constant investment in innovation, says AfriSam Process Engineer Marieta Buckle. It is also important to consider the cost implications of any changes, given South Africa’s need for a just transition to a sustainable future.

“In our position as a developing country, our future will demand the construction of millions of houses – structures that require considerable quantities of cement,” says Buckle. “The way we pursue our just transition must take into account the affordability of these homes for the vast majority of citizens.”

AfriSam has therefore been cautious in how it sets and publicises its sustainability targets, while all along continuing to prioritise research and development into how to achieve lower carbon products. Having considered a wide variety of options available, it has implemented strategies that have the least cost impact on customers and the market. 

Client Focus

IPR CUSTOMERS PRAISE HINGED DOOR CONCEPT ON ATLAS COPCO PUMPS

A patented hinged door on Atlas Copco’s diesel driven dewatering pump sets saves users time and trouble, ensuring there is no longer any excuse to avoid regular inspection and maintenance.

“The simple but brilliant hinged door concept has meant a massive improvement in ease of maintenance for users of these end-suction dewatering units,” says Steve du Toit, IPR Product Manager for Atlas Copco. “It reduces the downtime required for inspection and servicing of Atlas Copco’s PAS and PAC pumps, as it requires none of the traditional equipment that was normally involved to safely lift and move large pump covers.”

An individual technician can now conduct inspections and maintenance on their own – a job that previously required a team with appropriate heavy lifting equipment to open and handle the end-suction cover. Depending on the size of the pump, it would also have required certain certified rigging equipment and a mobile crane or forklift. 

“With the hinged door, you need none of these items,” explains Du Toit. “The technician simply loosens the bolts on the cover, and swings it open on the hinge – gaining access to the impeller within as little as three minutes.”

By facilitating frequent inspection, the hinged door can actually benefit the user by lowering their total cost of ownership by ensuring that they don’t have to replace pumps prematurely.
By facilitating frequent inspection, the hinged door can actually benefit the user by lowering their total cost of ownership by ensuring that they don’t have to replace pumps prematurely.

This makes the feature very useful in applications varying from mining to agriculture. In mining, he highlights the strict safety compliance requirements that make it essential to use the proper lifting equipment for heavy pump end-suction covers. Where pumps are used in the agricultural context, it is often difficult to get the required lifting equipment into the remote locations where pumps may be operating. 

“The quick and easy access to the wear plates, the impeller and the mechanical seal is particularly important in applications where the pump is expected to run continuously – where it must not be stopped for any length of time,” he says. “The patented hinged door drastically reduces the inspection time, so that it can be returned to work much more quickly.”

South Africa’s market response to date has been enthusiastic, he says. Perhaps the greatest contribution of the hinged door innovation is that it allows users to check and service pumps regularly – when in the past it was such an arduous task that it was often just avoided. 

“Of course, this regular maintenance has a positive long-term impact on the pump’s performance, reliability and lifespan,” he says. “By facilitating frequent inspection, the hinged door can actually benefit the user by lowering their total cost of ownership by ensuring that they don’t have to replace pumps prematurely.”

Client Focus

SPIRES SHOOT SKYWARD AS MSIKABA BRIDGE ADVANCES

The pylon spires of South Africa’s Msikaba Bridge mega project are on their way up, soon to tower almost 130 metres high at each side of the near 200m deep river gorge. 

For Laurence Savage, Concor’s Project Director on this contract, this momentous phase will reveal the sheer grace of the Msikaba Bridge design, and the awesome scale of the development. The Msikaba Bridge forms part of the South African National Roads Agency Limited’s (SANRAL) N2 Wild Coast project and is being constructed by the CME JV, a partnership between Concor and MECSA, both 100% black owned Grade 9CE South African construction companies.

With construction of the pylon spires underway at the Msikaba Bridge project, the scale of the development is quite apparent.
With construction of the pylon spires underway at the Msikaba Bridge project, the scale of the development is quite apparent.

Currently being slip-formed from the bifurcated legs of the pylons, each of the spires extend 95m from the bifurcation to the top of each pylon – taking the height of the bridge pylons to 128m. 

“The inverted Y-shape of the concrete pylons is strikingly elegant, and will become a hallmark of this iconic structure – as the design is architecturally elegant, diverging from the foundation legs, up towards the bifurcation and symmetrically converging to the top of the spire,” says Savage. “This is the largest cable-stayed bridge to be built in South Africa, and probably one of the most complex engineering bridge projects yet executed in Africa.” 

Like the legs of the bridge pylon, the reinforced concrete spire is hollow to reduce weight and is formed in a tubular design improving its strength-to-weight ratio.
Like the legs of the bridge pylon, the reinforced concrete spire is hollow to reduce weight and is formed in a tubular design improving its strength-to-weight ratio.
The pylon lifts are accomplished using a jacking system for the formwork shutters with eight jacks around the circumference of the spire.
The pylon lifts are accomplished using a jacking system for the formwork shutters with eight jacks around the circumference of the spire.
The inverted Y-shape of the concrete pylons at the Msikaba Bridge project is strikingly elegant and will become a hallmark of this iconic structure.
The inverted Y-shape of the concrete pylons at the Msikaba Bridge project is strikingly elegant and will become a hallmark of this iconic structure.
Each spire will extend 95m from the bifurcation to the top of each pylon
Each spire will extend 95m from the bifurcation to the top of each pylon

In this design, each pylon rests on two inclined legs which meet 21m from the start of the bifurcation which extends a full 11m. At 32m, the first section of the spire – starting with a diameter of six metres – is uninterrupted for 55,7m and comprises 14 slipform lifts. Then begins the inclusion of 17 anchor inserts over the next 35m of the spire, which reaches a height of 124m and will have converged to a four metre diameter. These anchor inserts accommodate the 17 cables that run from the anchor blocks located behind each pylon to the spire, and then down to the 580m long bridge deck. 

“To accomplish the lifts, we are using a jacking system for the formwork shutters, with eight jacks around the circumference of the spire,” he explains. “Each lift is 3,6m conducted at intervals of about two weeks per lift and we are making steady progress with quality and safety being paramount.”

The work is accessed using a specialised stair system, with one set of access stairs from ground level to the top of the bifurcation and a second stairwell to follow the shutter system up the spire. The formwork system comprises three decks that trail below each other; the interlinked decks lift together as the shutters are jacked up.

“The depth of the gorge – at around 197m – means that no work on the bridge deck itself can be done from ground level,” he continues. “Everything has to be done suspended from these two pylons – one on the south side of the gorge and one on the north side of the river.”

Like the leg of the bridge pylon, the reinforced concrete spire – with walls a metre thick – is hollow to reduce weight and is formed in a tubular design that significantly improves its strength-to-weight ratio. The reinforcing bar used in the spire includes 12 to 16 mm bar as lacing, with primary bars of 30 and 40mm bar employed in high densities to carry the significant loads. 

“Once the stays and bridge are in place, the load on each pylon will amount to around 7,000t,” he points out. The pylons are well advanced, with about half of the planned concrete volumes already poured by the top of bifurcation. After the last anchor insert, a four metre parapet will be constructed around the very top of the pylon spire. Access to the inside of the pylon will be restricted to engineering inspections and maintenance. 

“Indicative of the precision engineering being employed on this project is the number of activities that must take place at the same time – in a confined area,” Savage explains. “By the time we have completed the fifth anchor insert, for instance, we will have begun the launching of the first deck segment – followed shortly by the second and third segments. While these activities are taking place, the spire and inserts will continue to be erected and cast.”

Savage emphasises the intense focus on safety that has characterised the project, in line with Concor’s Zero Harm policy and protocols. Despite the high risk site which has included excavations of up to 17m for the pylon anchors, the site team recently achieved 3,5 million Lost Time Injury Free hours. Preparation for working at heights is a particular priority, with specialised training mandatory for these activities.

“This is all part of a training regime around safety, where we are continuously conducting risk assessments with our workforce,” he says. “The first item for discussion every day on site is the safety of their working environment; our primary value is care – both for yourself and for others.”

Savage highlights that when the bridge deck commences launching across the gorge later in the year, the culture of safety – inculcated in all workers over the previous years of the project – will be second nature to all. This philosophy applies across the approximately 300 people working on the north and south banks of the bridge, with some additional 280 people currently engaged in various community and local upliftment projects in the vicinity and a further 80 people in the engineering team and laboratory support staff. 

Client Focus

HOW WEG VSD TECHNOLOGY CAN HELP DEAL WITH LOAD SHEDDING

Variable speed drives (VSDs) are generally considered as vital contributors to energy efficiency, but they also have features that can reduce the operational disruptions caused by load shedding. 

“Any industrial operation that relies on electric motors will face severe challenges to their continuous workflow when load shedding strikes,” says Pieter de Villiers, Gqeberha branch manager for Zest WEG. De Villiers was previously the VSD Service Manager at the company. “Much of the disruption is related to the process of starting machinery up again after a power loss, which often must be conducted as a series of sequential actions that an operator must oversee and implement.”

Pieter de Villiers, Gqeberha branch manager for Zest WEG.
Pieter de Villiers, Gqeberha branch manager for Zest WEG.

What many motor users are not aware of is the usefulness of WEG VSDs in automating and controlling this start-up, explains de Villiers. WEG VSDs can be programmed to initiate a sequence of actions, so that this does not have to be done manually by the operator. A simple example to illustrate his point is where water is being pumped through pipelines which drain out during load shedding. In most cases, the pumps cannot simply be started up again at full speed in a ‘dry’ condition without the risk of cavitation and other damage.

“In cases like this, the WEG VSD can be programmed to start the pump at a lower speed until the pipeline is full of water, after which it could resume full pumping duties,” he says. “Similarly, it is important for a siren to be sounded on a mining operation before a conveyor system is re-activated after the start of load shedding for safety reasons. The WEG VSD can also be programmed to automate the re-start process, and it initiates the siren to warn staff that the conveyor will be running again.”

He highlights that the full range of WEG VSDs have built-in PLC capability, allowing them to be programmed in this way – without the need for PLCs to be added to the system. Another function of VSDs that makes them valuable assets in times of load shedding is to prevent equipment from tripping out. This can happen when there is too much ‘dead time’ between grid power turning off and a back-up generator kicking in. 

A range of WEG Variable Speed Drives that can prevent equipment from tripping out during load shedding.
A range of WEG Variable Speed Drives that can prevent equipment from tripping out during load shedding.

“If dead time lasts more than a few seconds, many motor-driven applications can trip out and require a re-start which can be time consuming and labour intensive. A common way that the VSD stays live during this dead time is through the stored energy in its capacitors, allowing it to then re-accelerate the motor when the generator kicks in,” he explains. “It is also possible to set up the drive to utilise the inertia from the load and therefore power from the motor itself – essentially using the motor briefly as a generator to keep the VSD alive.”

WEG VSDs also play a useful role when energy users want to harness renewable energy sources like solar power. In a hybrid power system where a motor is connected to both the grid and to solar panels, a VSD can utilise the best source to feed the motor. If there is sufficient sunlight, the system will detect the power flowing in from the panels and optimise that power source. 

“On the other hand, the VSD will switch to grid power at night or when it is cloudy,” says de Villiers. “This allows motors to be kept running while reducing the cost of energy, and also reducing the user’s carbon footprint.”

Client Focus

SEW-EURODRIVE MACC GEAR UNITS KEEP POWER STATION COOL

Recently installed in a power station, 24 of SEW-EURODRIVE’s MACC-Series two-stage gear units for air cooled condensers are ensuring adequate air movement to cool circulating water so that power generation can continue.

This cooling function had become a challenge for the power station when the previously installed competitor products had repeatedly failed unexpectedly. SEW-EURODRIVE had installed these MACC units over the past few years, and their reliable operation has led to a request to supply several additional units. According to SEW-EURODRIVE Business Development Representative Quintin Bianchina, the design is specific to this demanding application.

SEW-EURODRIVE’s MACC-Series two-stage gear units for air cooled condensers ensure adequate air movement to cool circulating water so that power generation can continue.
Comprising a gearbox and long output shaft that attaches to a fan via a hub, these MACC units also boast a thicker, more rigid cast iron housing than a standard gearbox.

“Comprising a gearbox and long output shaft that attaches to a fan via a hub, these MACC units also boast a thicker, more rigid cast iron housing than a standard gearbox,” explains Bianchina. “The radial and axial loads transmitted by the fan are substantial, requiring a suitable design that will withstand these forces.”

With the fan in operation, there is both upward and downward thrust as well as forces to the left and right. The flat topography and climatic conditions around the power station also exacerbate the situation, especially on hot days when air moves rapidly up the cooling towers. The gearbox, bearings and shaft must be designed and manufactured to accommodate these forces while continuing to operate reliably.

“This application is, in fact, so challenging that the customers’ existing equipment was not coping with the demands,” he says. “We were able to offer our world class engineering solutions to develop the MACC09 model – the largest version in this range – which has proved fit for purpose under these arduous conditions.”

The noise levels are an additional factor in this application, and the quiet MACC units ensure that they do not exceed maximum limits; the customer monitors the noise to check compliance. Heat build-up in the gearbox must also be dissipated, so the design includes cooling ribs to increase the surface area. This design enhances the cooling significantly on the gear units. SEW-EURODRIVE also offers a low noise axial cooling fan as an option, for enhanced thermal improvements.

Another vital aspect of the SEW-EURODRIVE’s MACC’s features is the maintenance safety brake on the high speed input section of the gearbox. This can be applied to bring the fan safely and easily to a standstill under wind milling conditions when maintenance is required. 

“Due to their size, these fans do not otherwise stop turning once they start – due to the natural upward airflow into the cooling tower,” he says. 

Since SEW-EURODRIVE has recently built a new and expanded facility at Aeroton in Gauteng, the assembly of these MACC units can be done locally. Enlarged stockholdings of components means that the turnaround time will be drastically reduced. 

“Rather than the usual 30+ weeks to import this equipment, we expect to assemble and deliver these in batches within 8 to 12 weeks,” says Bianchina. The MACC series is designed and tested by SEW-EURODRIVE’s centre of excellence for these products in Finland.