Bulk Handling Today March/April 2020 by Promech Publishing

BULK

HANDLING Endorsed by: CMA l LEEASA l SAIMechE l SAIMH Mar/Apr 2020

EFFECTIVELY THREE FORKLIFTS IN ONE FOR HEAVY LOADS

ADEQUATE SAFETY PRECAUTIONS AROUND BELT RUNAWAY

T O D A Y

BULK

HANDLING

T O D A Y

Endorsed by: CMA l LEEASA l SAIMechE l SAIMH Mar/Apr 2020

EFFECTIVELY THREE FORKLIFTS IN ONE FOR HEAVY LOADS

ADEQUATE SAFETY PRECAUTIONS AROUND BELT RUNAWAY

BULK

HANDLING Mar/Apr 2020

T O D A Y

Contents On the cover: Condra Marc Kleiner Tel: (011) 776-6000 Email: sales@condra.co.za www.condra.co.za

CMA News 4 5

Beltcon 20

Company Profile From the Desk

22 Assessment of the Braking Performance of Unidirectional Idlers

Cover Story

6 When to Replace and When to Refurbish

Power Transmission

Endorsing Bodies

Mining

•

CMA (Conveyor Manufacturers Association)

Coolant

•

LEEASA (Lifting Equipment Engineering Association of South Africa)

Materials Handling

•

SAIMechE (SA Institution of Mechanical Engineering)

Chutes

•

SAIMH (SA Institute of Materials Handling)

Effective Gear Reducer

10 Preventing Reverse Rotation 13 New Plant in Kitwe 16 Long and Bulky Loads 17 Solving Bottlenecks at Depth

Earthmoving

Market Forum

18 TLB versus Compact Excavator

All rights reserved. No editorial matter published in “Bulk Handling Today” may be reproduced in any form or language without written permission of the publishers. While every effort is made to ensure accurate reproduction, the editor, authors, publishers and their employees or agents shall not be responsible or in any way liable for any errors, omissions or inaccuracies in the publication, whether arising from negligence or otherwise or for any consequences arising therefrom. The inclusion or exclusion of any product does not mean that the publisher or editorial board advocates or rejects its use either generally or in any particular field or fields.

Our e-mail address is bulkhandling@promech.co.za Visit our website on www.bulkhandlingtoday.co.za

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Mar/Apr 2020

COMPANY PROFILE

Dymot Engineering Dymot Engineering specialises in the design and manufacture of a full range of winches and winching equipment for a variety of winching applications.

ymot's main area of expertise is winches for conveyor tensioning applications.

The company automatic take-up systems are widely used in the mining industry and involve using electric winches, strain gauges and programmable electronic controllers to control the startup and running tensions on any conveyor. These systems are extensively used underground where the conventional gravity tensioning systems are difficult to accommodate.

Can your take-up system supplier offer you these turnkey tensioning systems which may be counterweight maintenance, automatic tensioning or locked take-up solutions? The safety hand winch range employs an automatic clamping and ratchet type brake that is never disengaged thus ensuring complete safety when raising or lowering a load. These winches are extensively used on gravity counter weight tensioning systems for conveyors. Dymot Engineering prides itself on being a front-

runner in winching by constantly adapting to the latest technologies available on the market. This is evident in the newest developments on offer with their plant manoeuvring winches. These winches, complete with the swivel sheaves, are specially designed and developed for accurate positioning of plants or barges. They are extensively used in the mineral separation mining industry. Modern mining has created a demand to handle longer and wider belts. Dymot offers heavy duty conveyor belt reelers that can handle narrow to wide belts. These reelers can be handled with one unit that is adjustable for various belts widths. This a great advantage as one unit can service most conveyors on site. These modern high speed, large capacity, long length conveyors have also created a need for an alternative to gravity take up systems for tensioning. The company offers an electronic tension control system specifically for this purpose, with a variable frequency drive which offers multiple advantages. The selection of conveyor tensioning devices is critical to daily operation and the life of a conveyor system. We have also recently built one of the biggest braked capstans, to date, in the world. This was as per client specifications and was a double bullwheeldouble idler braked capstan with a brake capacity of 60 tons. Other areas Dymot specialises in include rail car moving systems (both endless rope & single type), hydraulic winches and rope sheaves. Dymot has designed and manufactured large barge moving winches (for mining plants) as well as mill rotating winches. The company has also manufactured a range of stage and construction winches for shaft sinking and tower building/sliding applications. Dymot Engineering Tel: (011) 970-1920, www.dymot.co.za (13)

Dymot Engineering Company (PTY) LTD Specialist Designers & Manufacturers of Winching Systems WORLD OF WINCHES

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Market leaders in conveyor tensioning equipment Take up winches with Overload Protection Gravity Counterweight Handling Braked Capstans Screw Take Ups Hand & Motorised Winches Electrical Control Panels & Systems Sheaves 11 DERRICK ROAD, SPARTAN, KEMPTON PARK SOUTH AFRICA +27 11 970 1920 sales@dymot.co.za www.dymot.co.za

CONVEYOR MANUFACTURERS ASSOCIATION

From The Chairman’s Desk The work (presented in the paper printed in this issue from pages 22 to 34) is derived from a Masters Dissertation undertaken at the University of the Witwatersrand, and facilitated by the CMA, that was aimed at investigating the performance of unidirectional idlers under different inclined conveyor belt operating conditions.

p until now, very little work has been done in researching the performance of unidirectional idlers. As such, the CMA commissioned a test rig to be used to measure the resistance to motion between an inclined belt and a set of idler rolls locked in place. The experiments conducted on this rig varied a total of seven belt conveying factors in order to investigate the effects of these factors on the measured unidirectional idler resistive force. In order to plan and analyse the experiments, statistical Design Of Experiment (DOE) techniques were employed in the design of a series of experimental programmes. Overall, it was found that material load, troughing angle and idler pitch have the most significant effect on the braking ability of unidirectional rollers. Additionally it was identified that although contact

Jay Pillay

friction affects unidirectional idler performance, the presence of non-friction resistances (such as belt sag) strongly influence resistive force at belt slip. Based on these findings, a conservative numerical method for specifying the required quantity of unidirectional idler rolls was derived through the separation of friction and non-friction effects and the use of experimental data. Jay Pillay, Chairman

Acknowledgements from the authors

The authors would like to express their deepest appreciation to all of those who contributed to the research presented in this paper. Special thanks to Simon Curry and the team at Flexco for their support in every stage of this research venture – from the initial stages of planning and equipment design, right through to commissioning and experimentation. Thanks also go to Dave Pitcher and everyone at Dunlop Belting Products for donating factory floor space for the UDR test rig and for the invaluable assistance of their maintenance team during commissioning and major experimental set-up changes, as well as for providing belt samples. Furthermore, thanks go to Bosworth for the construction of the UDR test rig, as well as Melco, Lorbrand, Megaroller and Dymot for the donation of idler frames, rolls, steel ropes and sheaves. Special thanks also to Beverly Claasens who vetted the structural design of the test rig. Last, but certainly not least, a very big shout-out to the CMA for funding the project in its entirety.

Membership at January 2020 All members subscribe to the CMA Code of Ethics Acrow Limited Actom Afripp Projects Altra Industrial Motion South Africa (Pty) Ltd Bauer Bearings International Belt Brokers Belting Supply Services BMG Bonfiglioli Power Transmissions Bosworth Brelko Conveyor Products CedoTech cc Closeal Manufacturing Collisen Engineering ContiTech South Africa (Pty) Ltd Conveyor & Engineering Equipment Conveyor & Industrial Supplies (Pty) Ltd Conveyor Watch (Pty) Ltd CT Systems David Brown Gear Industries DRA Projects SA (Pty) Ltd

Dunlop Belting Products Dymot Engineering Company ELB Engineering Services Electromote (Pty) Ltd Fenner Conveyor Belting (South Africa) Flexco SA (Pty) Ltd FLSmidth Roymec Habasit South Africa (Pty) Ltd Hägglunds Drives South Africa Hatch Africa (Pty) Ltd HMA South Africa (Pty) Ltd Hosch - Fördertechnik (SA) International Belting & Marketing (Pty) Ltd Iptron Technology cc KevConBelt (Pty) Ltd Leoka Engineering Lorbrand Magnet Service Binder CC Martin Engineering Melco Conveyor Equipment Merlin consulting (Pty) Ltd Moret Mining

Nepean Conveyors OE Bearings Oriental Rubber Industries SA Osborn Engineered Products Pegasus Industrial Services cc Rema Tip Top South Africa Ringspann South Africa Rossi Gearmotors (Pty) Ltd Rula Bulk Materials Handling SENET SEW Eurodrive Shaft Engineering (Pty) Ltd SKF South Africa Tenova Takraf ThyssenKrupp Industrial Solutions South Africa (Pty) Ltd Timken South Africa (Pty) Ltd Transvaal Rubber Company Voith Turbo Weba South Africa (Pty) Ltd WorleyParsons RSA Zest Electric Motors

BULK HANDLING TODAY

Mar/Apr 2020

When to Replace, And Is it better to replace or refurbish an overhead crane reaching the end of its life?

t least one South African firm reckons that there are advantages to both options, and Condra, a specialist in new crane manufacture as well as crane refurbishment, believes that the choice should be very carefully considered. According to Marc Kleiner, the company’s managing director, refurbishment allows the customer to immediately realise a cost saving over buying new, and carries the additional advantage of providing an as-new machine already familiar to his operators, avoiding any need for re-training. Production can continue as before, with no change to established procedure. Buying new, on the other hand, offers the advantages of lower operating costs quickly realised, a reduction in projected overall lifetime cost, and more efficient operation as a result of newer cranes’ increased speeds, lower weights and lower electricity consumption. According to Marc, hoists today are as much as 50% lighter than they were 30 years ago, and the consequent reduction in crane weight also reduces the rate of wear on the overall factory structure.

Condra refurbishes not only its own cranes, but also competitors’ machines Signs that an overhead crane will soon need either refurbishing or replacing include brittle electrical cable loop systems, failing contactors, extreme wheel wear, structural cracks and a general increase in maintenance costs.

soon to be refurbished at Condra’s Germiston factory, which will either re-engineer or re-manufacture any parts that are either no longer available or which will take too long to import.

Dismantling

Recent refurbishments of Condra’s own overhead cranes have included an 80-ton machine for Sishen, and two hoists and a 25-ton, 20-metre-span crane for Implats, the latter involving conversion of the existing electrical configuration from 525V to 400V. The refurbishment of Sishen’s 80 tonner was more routine, with all bearings, ropes and brake linings being replaced, and the usual checks and inspections carried out before the crane was re-painted and delivered back to the mine.

Condra refurbishes not only its own cranes, but also competitors’ machines.

Apart from its own machines and competitors’ cranes, Condra also refurbishes overhead machines originally supplied by companies that have recently closed.

If the customer should decide to refurbish, then the procedure generally comprises a dismantling of the crane followed by inspection of all brakes and mechanicals, a change of bearings, and an assessment of the overall crane structure using MPI to inspect critical sections for rust. Crane girders and crabs are also re-aligned, and the girders checked to ensure that they remain true. All main components are then shot-blasted, reassembled and painted.

Marc explains that competitor crane refurbishment is becoming increasingly popular because it allows the circumvention of delays caused by long component lead times of up to 18 months. Such delays are common among European companies because they have to import their spares.

Re-engineer

As an example, Marc points to a 20-ton crane originally manufactured by a German company but

Refurbished 20-metre-span Condra crane for Implats

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Mar/Apr 2020

Marc states that the benefit Condra gains during refurbishing, whether one of its own machines or one from a rival firm, is that its engineers can ascertain from a technical perspective precisely how the machine has been performing. “If the crane is our own, then we get the chance to look inside it, examine wear rates and make projections of expected component life,” he says.

COVER STORY

When to Refurbish the benefits. Examples are when a crane is very old (35 years or more), or when a crane has been working in the open and rust has established itself inside the girders. “So the customer first has to consider the estimated price difference between new and refurbished,” he says, “and then he has to weigh the extra cost of a new crane against the benefits of increased crane speed and consequent gains in productivity.

One thing we’re seeing is that Condra’s component life expectancy presently far exceeds the international norm “To help the user with this decision, we supply a range of solutions offering varying productivity gains, with alternative costs for each one.” Marc says that customers are almost always offered the option during refurbishment of technically upgrading their machine. He explains that the productivity of cranes of 20 years or older can usually be improved through increased speed and easier acceleration and deceleration, all achieved through the installation of variable frequency drives. Enhancements can also be fitted, such as a digital read-out on the load, or remote control if the machine does not already have this option.

Modern technology

“One thing we’re seeing is that Condra’s component life expectancy presently far exceeds the international norm, and we will be reducing the size of some of the components for our 2025 models to improve efficiencies and reduce power consumption, especially within the gearboxes.”

Capacity and span

Marc explains that overhead cranes are sent back to the factory for refurbishment anywhere between 15 years and 30 years after commissioning, depending on the operator’s maintenance policy and how hard the crane has been working. He points out that Condra offers the option of changing both crane capacity and span during a refurbishment by fitting new hoists, changing the rope and modifying the gear reduction. “Whatever the case, whether upgrade or refurbishment of a Condra crane or a competitor’s crane, or one from a company that has closed, we work closely with the client on a solution that will deliver back a fully reliable, fully refurbished machine that will work happily for many years into the future.”

Price difference

He points out that refurbishment is not always the better option, with the cost sometimes outstripping

“So with refurbishment we can give back to the customer a crane that is much faster and much lighter than it was before, and we can fit a frequency drive on the long travel to speed it up, and we can incorporate in the refurbishment any kind of modern technology that he wants, including hoists of different capacity,” he adds. “We can also automate the crane during refurbishment, in which case we often improve the mechanicals to incorporate the new electrical equipment needed for automation. “These options are offered across the board, from standard 2M workshop cranes to the higher performing machines such as Class 3 and Class 4.” Marc concludes by saying that the time needed to refurbish a standard workshop crane is approximately two weeks, while heavier-duty cranes need anything up to six weeks including time for re-painting. All refurbishments carry a warranty of two years on machines originally manufactured by Condra, and one year for cranes made by a competitor. Condra (Pty) Ltd Marc Kleiner Tel: (011) 776-6000 Email: sales@condra.co.za www.condra.co.za

BULK HANDLING TODAY

Mar/Apr 2020

POWER TRANSMISSION

Effective Gear Reducer The outstanding performance of ABB’s Dodge gear reducer at Kwena Coal Mine in Mpumalanga has led to leading distributor Bearings International (BI) continuing its successful business relationship with this Swiss-Swedish mul-tinational through the purchase of a second unit to be installed on another key conveyor.

BB has a long-standing agreement to plan inventory for the ABB Dodge Torque Arm II (TAII) gear reducer supplied to Kwena Coal mine, with ongoing discussions and planning underway for a third installation. The mine initially purchased an TAII from BI in 2013, at a time when it was looking for innovative solutions to increase operations efficiencies and lower production downtime. The gear reducer is used in the drive mechanism of a 200-m-long, 600-mm-wide coal conveyor carrying 700tph of coal. This main conveyor is a critical application, feeding coal into the wash plant.

Featuring inner seals made form hydro-genated butadiene nitrile rubber (HBNR) on the input and output shafts “An excellent relationship with the end user and a branch in close vicinity allows for this site to be used as a reference when engaging with users from other sites. The end user was and continues to be highly satisfied with the reliability, minimal maintenance required, and longevity of the unit,” says BI Offer Marketing Manager Victor Strobel. The shaft-mounted TAII gear reducer mounts directly onto the driven shaft and is ideal for tough applications where a long operating life is essential, making it a perfect solution for a coal mine like Kwena. The reducer can also be used in a range of environments due to the many accessories available. Discussions are underway for a third ABB Dodge TAII gear reducer at Kwena in Mpumalanga

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Manufacturing principles

These reducers are

Victor Strobel

manufactured at the ABB Greenville Plant in South Carolina in the US to American Gear Manufacturers’ Association (AGMA) standards, utilising only heavy-duty tapered roller bearings throughout the unit for an average bearing life of 25 000 hours at a 1.0 service factor. The units adhere to strict manufacturing principles, ensuring quality and consistency in the manufacturing process. Regular quality checks are performed throughout the process, ensuring materials and finished components meet requirements consistently. All the gear reducers are subject to final test runs upon assembly to ensure all parameters are within technical specifications. A key feature of the TAII gear reducer is the advanced dual-seal system, featuring inner seals made from hydro-genated butadiene nitrile rubber (HBNR) on the input and output shafts. The heavy contact seals’ primary function is to retain oil inside the reducer.

Dust and debris

The light-contact seals are fitted outward from the heavy contact seals so as to keep dust and debris away from the inner seal, prolonging the life of both. The HBNR material has an operating temperature range of -40°C to 150°C, and shows less wear on the shafts than other types of seals with similar high points. The TAII gear reducer utilises a twin-tapered bushing that eliminates fretting corrosion, and makes fitment quick and easy with regular hand tools, allowing the gearbox to be removed quickly should the need arise to change a conveyor pulley or the conveyor pulley bearings between the gear reducer and the pulley. Spares are simplified, since various shaft sizes can be accommodated by a single gear reducer, which means there is no need to stock a gear reducer for

each shaft size on the plant. Stores simply need to keep common reducers and associated bush kits on hand.

Backstop

Having an externally accessible backstop means direction changes can be easily achieved in the field without needing to disassemble the gear reducer. These backstops are compatible with oils containing extreme pressure (EP) additives. The complete lift-off design ensures zero drag or shaft wear once up to operational speed.

Spares are simplified, since various shaft sizes can be accommodated by a single gear reducer, which means there is no need to stock a gear reducer for each shaft size on the plant Pry slots along the mating surface ensure the reducer can be repaired easily, without damaging the case. Service parts are available in different levelled kits, taking the guesswork out of which part to replace. Also making the unit fully serviceable rather than just disposable.

The ABB TAII gear reducer is used in a critical conveyor application, feeding coal into the wash plant

BI Tel: (011) 899-0000 Email: info@bearings.co.za www.bearings.co.za

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Mar/Apr 2020

MINING

Preventing Reverse Rotation New to BMG’s range of Tsubaki cam clutches, is the BS-F series, designed for high-speed inclined and long overland belt conveyors and bucket elevators used in the mining and bulk handling sectors.

subaki backstop cam clutches are designed to prevent reverse rotation of drive shafts, offering a simple and cost-effective means to protect capital equipment and enhance safety.

Space saving and quick installation

“The new high-torque, high-speed Tsubaki BS-F series, with a narrow width I-beam torque arm, is a drop-in replacement to conventional anti rollback devices. This allows for quick and easy on-site installation and enables the replacement of an old backstop with the new BS-F design, without the need for modification to the existing layout,” says Gavin Kirstein, National Tsubaki Product Specialist, BMG.

Although this series has a narrower width than other models, the downsized unit exceeds the requirements of high-speed inclined belt conveyors, with the benefits of space-saving and reduced installation time “Although this series has a narrower width than other models, the downsized unit exceeds the requirements of high-speed inclined belt conveyors, with the benefits of space-saving and reduced installation time.

“A common cause of conventional backstop failure is oil leakage. Tsubaki has eliminated this risk in the new BSF series by designing the backstop to operate with grease and a specially- designed labyrinth seal. The absence of an oil level gauge creates a more reliable safety device,” continues Gavin.

Operates in any environment

Important features of this series include a non-rollover cam and roller design, which offers higher backstop torque capacities and lower running temperatures than conventional anti rollback devices. Added to this, a flexible labyrinth seal mechanism prevents the ingress of dust and water in abrasive conditions and a double-lip oil seal and multi-temperature grease enable safe operation at a wide ambient temperature range, from - 40°C to + 65°C. The cam and roller cage orbit at low speed, continually conveying grease internally from the bottom to the top of the mechanism. The constant circulation of grease minimises internal friction and reduces operating temperature for dependable operation. Maintenance intervals are between 7 500 hours and 8 000 hours and the effective service life of the units is also significantly extended compared with conventional oil-filled units. BMG Gavin Kirstein Tel:(011) 620 7558 Email: gavink@bmgworld.net www.bmgworld.net

New to BMG’s extensive range of Tsubaki cam clutches, is the recently launched BS-F series, designed for high-speed inclined and long overland belt conveyors and bucket elevators used in mining and bulk handling sectors

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COOLANT

New Plant in Kitwe Cummins Zambia has completed a coolant plant project in Kitwe on the Copperbelt that received approval from the Zambia Environmental Management Agency (ZEMA) in 2019. The ‘plug-and-play’ plant will produce two types of coolant, namely ES compleat Hybrid (Blue) and ES compleat OAT (Red). PLC-driven and automated, the plant has the capability to carry out batch correction.

t has a blending capacity of around 1 600 litres over two hours, including quality testing. The system has two 2 500 litre product tanks for product storage.

Originally planned to be completed within six months in 2018, delivery and manufacturing logistics ultimately resulted in the project taking about a year to complete, in addition to the stringent ZEMA approval, John Kambing’a, Cummins Aftermarket Leader (Zambia) reports. The main contractor was CP Engineering, with a Cummins Filtration team overseeing the project from start to finish.

Customers will also have the option of bulk supply, which will drastically reduce their storage challenges in having access to sufficient product as and when required, and eliminate long lead times Cummins Filtration built the plant and shipped it to Zambia, where it was installed by a local contractor under the supervision of the project team. The Cummins Filtration team from South Africa also played a key role in commissioning the plant.

Impact assessment

“It is a requirement in Zambia to conduct an impact assessment for any project being undertaken. Therefore, the ZEMA approval was necessary to ensure that the coolant plant had no impact on the environment or the surrounding community,” John explains. To date, Cummins Zambia’s main coolant customer has been First Quantum Minerals (FQM), a major copper producer in the region. The new plant will allow Cummins Zambia to supply coolant to other customers in different packages.

“This will grow our filtration sales in Zambia, and allow us to serve other customers. It will also take care of our counter-sales customers. Other Cummins distributors and dealers wanting to take advantage of our cost-competitiveness will also be welcomed,” John highlights.

Different packages

The main benefits of the new coolant plant are that customers will not be restricted to obtain the products only in totes, but can request different packages according to their specific requirements. Customers will also have the option of bulk supply, which will drastically reduce their storage challenges in having access to sufficient product as and when required, and eliminate long lead times. Switching to in-house coolant production at Cummins Zambia will reduce import costs significantly, allowing it to pass these savings onto customers. Meshach Kwegyir-Aggrey, GM Cummins Zambia, elaborates that, with the new coolant plant at Zambia, what we have succeeded in doing is to basically halt the importation of water, which forms more than 90% of the coolant product, from South Africa into Zambia. This will also assist us to serve diverse markets, with volumes ranging from five litres to 1 000 litres. We will also increase our footprint in the Zambian coolant market and offer more value to customers.”

Cummins Deepa Rungasamy Tel: (011) 589-8512 Cell: 072-630-7501 www.cummins.com

The plant has a blending capacity of 1600 litres over two hours and two 2 500 litre product tanks

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“THE LINK FOR AFRICAN TRADING”

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TRANSNET FREIGHT RAIL

www.transnetfreightrail-tfr.net

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MATERIALS HANDLING

Long and Bulky Loads The Combilift C-series multi-directional forklifts have been well-received by the local market, particularly for handling long and bulky loads.

“

Combilift multi-directional forklifts, which have been designed for safe, space-saving and productive handling, improve workflow efficiencies and maximise storage space,” says Marius Schutte, managing director, Shamrock Handling Concepts, exclusive distributors in southern Africa of the Combilift C-Range of multi-directional forklift trucks. “These versatile machines, which are effectively three forklifts in one machine (a counterbalance forklift, narrow-aisle truck and side loader) eliminate the costs involved in double handling and thus optimise productivity. “These forklifts, with four-directional technology and effortless manoeuvrability, operate efficiently in confined areas and are able to quickly change the direction of travel, even in tight corners. Long, heavy and awkward loads are carefully transported down narrow aisles, through doorways and around objects, with no damage to the materials being handled, or the surroundings.

Integrated platform

“Shamrock’s customisation service also includes assistance with optimising the layout of a warehouse, through space-saving solutions. By utilising the advantages of the Combi C-range, storage

capacity of a site is maximised.” The C-series has a loading capacity of 2 500 – 25 000kg. These machines have a low centre of gravity and an integrated platform that provides a stable base on which to rest long loads, like planks, ceiling boards, steel, pipes and tubes during transport. Because there is no need to carry the load at elevated levels, safety is significantly improved.

Clear visibility

Standard features of this range include a rubber mounted cabin, load-sensing steering, a 4-way lever positioning of wheels and 3-wheel hydrostatic drive. The cab is mounted to the side of the mast, giving the operator clear visibility of the surroundings, forks and load. The moving mast system and the option of a hydraulic forklift positioner allows the operator to adjust the forks, reach out and lift and place the load, without having to leave the cab. These robust forklifts operate safely indoors and outdoors, in all weather conditions. Shamrock Handling Concepts is also the sole distributor of Moffett truck mounted forklifts and supplies other leading brands, including TCM, Combilift, Aisle-Master and Agrimac forklift trucks. Shamrock Handling Concepts (Pty) Limited Marius Schutte, Divisional Managing Director Tel: (011) 953-6807 Email: info@shamrock.co.za www.shamrock.co.za

The Combilift C-series multi-directional forklifts - available from Shamrock Handling Concepts - have been well-received by the local market, particularly for handling long and bulky loads.

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CHUTES

Solving Bottlenecks at Depth Bottlenecks were preventing one of the world’s deepest gold mines from achieving its targeted throughput on a level 2 850 metres below surface. Weba Chute Systems designed and manufactured the solution.

short slew conveyor was at the centre of the South African mine’s challenge, providing the only source of ore from that level. Frequent stoppages from belt cuts on this conveyor, often from large rocks stuck in the bottom of the existing chute, meant costly downtime and disrupted material flow to the plant.

The belt on the slew conveyor was also being regularly damaged by the high direct impact of rocks falling from the previous chute The solution, according to Dewald Tintinger, technical manager at Weba Chute Systems, was to design a completely new chute solution that would remove the need for the slew conveyor arrangement.

Custom design

“The chute we designed has a bypass leg that drops waste material directly into the bypass, while allowing an inline channel of reef onto the conveyor belt,” says Dewald. The custom-designed chute was able to replace the mechanical moving component, which also improved the safety of the working area. The solution, which also involved 70 metres of conveyor belt extension, required the new chute to bifurcate the flow of material from the stopes into a reef stream and a waste stream. “We achieved this by installing a chute section

mounted on a trolley frame, actuated to split the material flow as required,” Dewald elaborates. Another benefit was that the area no longer needed regular cleaning. Previously, four shifts of cleaners, comprising four workers each, were required to service the area around the slew conveyor and remove spillage. Weba Chute Systems technical advisor Alec Bond says the belt on the slew conveyor was also being regularly damaged by the high direct impact of rocks falling from the previous chute. “Our flow-controlled chute design ensures that the chute has no free-dropping material,” he says. “Instead, the speed of the material is controlled all the way through, right up until the outlet onto the belt.”

No parts

The free-falling material was also causing regular damage to the chute itself, requiring frequent liner changeouts. By contrast, this Weba chute requires little maintenance. After a year and a half of operation, the mine has not had to replace any of the parts. Alec highlights how the underground location of the project added considerably to its complexity. Space at the point of installation was limited, with irregular angles and levels being imposed by the sidewalls and hanging wall. There were also constraints regarding the size of components that could be transported underground, either inside or hanging from the lift cage. “Every component had to be designed with logistics in mind,” he adds. Weba has a custom-design capability and has an ISO 9001:2008 accredited local manufacturing facility, combined with inhouse expertise and years of materials handling and transfer point experience.

In stages

Installation of the new system had to be conducted with minimal impact on mine operations. It was therefore installed in stages while the plant was operational. The shutdown of the plant took place over the December period, as this was the only time available that would not disrupt production. “This required us to design the chute and associated structures in such a way that we could build it underground while the plant was running,” Alec explains. Construction took place over a six month period alongside the operation of the slew conveyor. “At the commencement of the shutdown, the changeover was done and the previous conveyor arrangement removed,” he concludes. “No production was lost during the installation of the new chute and system.”

A transfer point solution to prevent bottlenecks on one of the world's deepest gold mines

Weba Chute Systems & Solutions www.webachutes.com

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EARTHMOVING

TLB versus Compact Excavator The backhoe loader, better known as the TLB in our local circles, has always been deemed the trusted ‘pick and shovel’ of the local construction industry, and continues to dig its way onto local sites. However, in line with global trends, the compact excavator is continuously digging for a sizeable share of the market as the move towards compact solutions on African sites continues to gain pace.

he ever-growing trend towards smaller construction equipment is at this point anchored by mature markets, where about 70% of total equipment sales are driven by compact ranges. In Africa, the opposite is true; 75-80% of machines sold are still heavy ranges. However, there is a gradual growth of smaller machines in Africa.

We are slowly moving towards the European ratio and we believe the potential is massive for compact excavators and compact equipment at large Exact opposite A few years back, the local sales ratio was a single compact unit for every 20 heavy machines (20-t plus). In Europe, it was the exact opposite; 20 compact units for every single large excavator sold. "We are slowly moving towards the European ratio and we believe the potential is massive for compact

Tom Bloom, Director for Construction Equipment at Smith Power Equipment

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excavators and compact equipment at large," says Tom Bloom of Smith Power Equipment.

Bread and butter "We would all agree that generally the TLB has for years been the trusted solution for the industry, accounting for a sizeable chunk of the total equipment sales in South Africa. This machine is by far the ‘bread and butter’ line in the construction and plant hire industries." The versatility of the TLB has made it a machine of choice on construction sites where applications call for digging and loading of material. While the TLB has long been a staple on many job sites, in recent years, more contractors are opting for a mini excavator instead. "Both machines have their own benefits, but understanding your jobsite applications is the key to making the right decision for your job," Tom comments.

Ask the right questions It is very important to ask the right questions because these two machines differ greatly in versatility, mobility and transportability. "Be sure to assess the pros and cons before you make that important buying decision. The three key questions to ask yourself should relate to the right machine for the application at hand, the size of the jobsite and the distance between sites, among other considerations." Backhoe loaders can perform not only trenching, lifting, excavating and loading jobs, but they can also travel at higher speeds in a wide range of applications. On the other hand, mini excavators are compact and lightweight to minimise track marks and top ground damage, especially in sensitive working areas.

We believe that it’s only a matter of time before the compact excavator becomes the prime tool of choice considering the comparative production speeds In terms of job site size, TLBs can travel easily across a job site to complete more than one task, and an extended line of work tools improves versatility. Meanwhile, mini excavators can fit through small gates and around crowded sites to complete jobs in tight spaces, like occupied parking lots and indoor projects.

130-140 units strong, with model ranges varying in size and capacity. "We believe the compact excavator sector is the only market currently showing some type of opportunity for growth although the total volume is not the biggest in the compact machinery sector," Tom adds. "There are application opportunities in plumbing, electrical and telecommunication, as well as in the specialised agricultural sector. At Smith Power, as demonstrated by our focus on compact machines for many years, we believe that the future lies in supplying both compact excavators and TLBs to the market. "However, we don’t necessarily believe that the compact excavator will entirely replace the TLB. The two solutions will co-exist together. It just depends on what you are doing, where you are doing it and how much space you have," he concludes. Smith Power Equipment JHB Branch Robert Keir Communications Officer Tel: 011 284 2000 Email: robertk@smithpower.co.za Web: www.smithpower.co.za

With manoeuvrability in mind, the mini excavator is more versatile in a lot of digging situations, but keep in mind that with a mini excavator comes a trailer and / or a truck to move it. The backhoe loader can be driven between sites.

The future While the TLB still offers an array of benefits and still continues to earn a spot in operators’ fleets, there is general consensus that the compact excavator is fast growing as a tool of preference on South African sites. Customers are benefitting from the versatility of small excavators on sites and increased productivity. "To give an idea, mid-sized units such as the 8-tonne (Kubota KX080) are taking trenching work away from the tried-and-tested TLB, and we believe that it’s only a matter of time before the compact excavator becomes the prime tool of choice considering the comparative production speeds." While the TLB continues to hold a sizeable share of the market, the next big thing may be the compact excavators. The market is growing significantly, accounting for a whopping 100 000 units a year globally.

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BELTCON 20

Assessment of the Braking Performance of Unidirectional Idlers Due to the inherent danger involved in the handling of bulk materials, it is vitally important that the associated safety risks are mitigated. A specific concern in this regard is the transport of material using steep inclined belt conveyors which are vulnerable to rollback and runaway. One such run-back preventing device is the backstop, which permits belt motion in the forward direction and prohibits it in the reverse direction. Backstops are usually mounted to the drive shaft of the head pulley and are effective in preventing runaways when the motor is not energised. However, when considering the event of a belt snap, a backstop is unable to stop the belt from accelerating down the incline.

Bryan Moore

Terrance Frangakis

ne particularly serious cause of a belt runaway occurs in the event of a belt snap which results in the loaded conveyor belt overcoming the rotational resistances of the idler rolls and accelerating down the incline. Figure 1 illustrates the repercussions of such a catastrophic event. Without adequate safety precautions in place, a belt runaway can lead to fatalities or injuries of personnel, damage to conveying equipment and loss of productivity. To avoid a calamity such as this, safety devices can be used.

To prevent this type of a runaway, unidirectional idlers may be used. These safety devices make use of high torque rated single-direction bearings installed within the shells of conventional idler rolls. This mechanism allows the roll to freely rotate in the forward direction, but prevents rotation in the opposite direction when the device is engaged â&#x20AC;&#x201C; effectively locking the roll in place. Figure 2 demonstrates this functionality.

Unidirectional idlers

Despite their use in industry, very little work has been done in researching the performance of unidirectional idlers to date. Considering the higher costs of these idlers, as well as the additional rotational resistance that they impart to the system, the importance of correctly specifying the required quantity of unidirectional idlers may be appreciated. In order to develop a better understanding of unidirectional idlers, the Conveyor Manufacturers Association of South Africa (CMA) commissioned a test rig to be built that could measure the resistance to motion between an inclined belt and a stationary idler. This test rig was designed to study the effects that the following list of belt conveying factors have on the performance of unidirectional idlers:

Figure 1. Schematic of a Conveyor Belt Snapping at the Head Pulley

Inclination angle (") Troughing angle ($ ) Belt sag (KS) Idler pitch (") Idler roll type (Îź) Idler roll diameter (D) Belt tension (T) Material loading (qm)

Literature review

Belt conveying factors: Considering unidirectional idlers as the solution to inherent safety concerns associated with steep inclined conveyors, the factors that possibly influence these safety devices will be explored in the following sub-sections.

Figure 2. Schematic Diagrams Illustrating the Functioning of Unidirectional Idlers

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Inclination Angle: When a belt is inclined, it is necessary to consider the relationship that material load and belt weight have on unidirectional idlers.

BELTCON 20 The force component of material load and belt weight acting along the incline increases with inclination, thus requiring more unidirectional idlers to inhibit belt motion. Troughing Angle: In a three-roll idler set, the troughing angle ($) is the angle created by one of the wing rolls and the centre roll (as shown in Figure 3). Different troughing angles result in different wing roll contact pressures. Previous research has shown that the normal force experienced at the wing rolls increases with increasing troughing angle. Ilic and Wheeler referenced research by Behrens which showed that the wing roll normal force is 1.2 and 1.9 times greater than would be expected with gravity acting alone on a wing roll troughed at 30o and 45o respectively. In terms of the effect that troughing angle has on the braking performance of unidirectional idlers, the greater normal force experienced by a wing roll troughed at a steeper angle will improve the friction braking capability of a unidirectional wing roll according to the following equation: where Ff is the friction force [N], Îź is the coefficient of friction and N is the normal force [N]. Despite the contact pressure multipliers observed in wing rolls, the majority of the conveyed material exists in the region above the centre rollers and as such, normal forces on these rollers tend to be larger. A recent study by Liu et al. recorded the total percentage of normal force on the centre belt section of a 35Â° troughed three-roll idler system to vary from 66.2% to 74.2%. As such, centre rolls should be prioritised in the

instillation of unidirectional devices. Belt Sag and Idler Pitch: The friction developed between a locked unidirectional idler and the conveyor belt is not the only factor that affects the resistance to motion of the belt. Instead, the inherent belt sag in the system (as depicted in Figure 4) requires additional pulling force to lift the belt up and over each successive idler set. Belt sag (KS) is the ratio of maximum vertical belt deflection ((max) to idler pitch ("), and is typically expressed as a percentage. Idler Roll Type: In the past, the material choice for idler roll shells was invariably steel, due to its availability and durability. In recent years, polymer shells have become more prevalent. The most frequently chosen polymer shells are made from Nylon and High Density Polyethylene (HDPE). With unidirectional idler performance in mind, it is intuitive that the belt and idler roll material combination (with its corresponding friction coefficient) will directly affect the friction braking capability of the unidirectional idler, according to Equation 1. Idler Roll Diameter: When it comes to the diameter of unidirectional idler rolls, this factor is likely to affect belt resistance to motion due to the development of indentation rolling and rotating resistance, and/or as a result of the relationship between beltroll contact pressure and the coefficient of friction. Indentation rolling resistance develops in conveyor systems as a result of the asymmetric compression of the belt bottom cover as it traverses over successive idler rolls, while idler rotating resistance develops as a result of the torsional resistance to rotation experienced by the roller bearing sub-assembly. Belt Tension: In the event of a belt snap, the complete release of conveyor belt tension is likely to result in considerable belt sagging between successive idlers. This, in turn, increases the force required to cause belt slip, thus helping to prevent a runaway. In terms of the experiments conducted in this research venture, tension was chosen as a variable in order to observe the effects of belt tension from a resistance to belt sliding point of view. This provided sufficient insight into the low/no tension case to be able to state whether the snapped belt would likely runaway in reality.

Figure 3. Three-Roll Troughed Idler System

Figure 4. Belt Deflection and Idler Pitch

Material Loading: The mass of material load per metre of conveyor belt (qm) plays a major role in unidirectional idler functionality. The greater the material loading, the larger the unidirectional idler normal force and associated friction will be. However, a larger load also results in a larger downslope component of weight which needs to be resisted by the unidirectional idlers (refer to Figure 2.b). Furthermore, in the event of a belt snap, the loss of tension in the belt and the downslope component of the material weight will increase the belt sag between idlers; thus assisting the unidirectional mechanism.

Design of Experiment Techniques

Figure 5. Half-Normal Plot for Hypothetical 2 3 Factorial DOE

When undertaking experimental research in which many parameters are varied, it is useful to employ statistical Design Of Experiment (DOE) techniques in order to identify the variables that have significant influence on a meaBULK HANDLING TODAY

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BELTCON 20 sured output, and to make better informed conclusions about the relationships between parameters and the measured outcome.

Figure 6. Interaction Effect Plot for Hypothetical 2 3 Factorial DOE

O f par t icular interest to this research are the DOE techniques associated with fractional factorial designs â&#x20AC;&#x201C; stud-

Figure 7. Diagram of the Resistive Force Measurement Technique

ies in which a subset of all the possible level combinations of multiple factors of an experiment are investigated. Once a carefully selected experimental design has been conducted, an analysis of variance may be performed to determine which factors (and interactions) have the most significant effect on the measured outcome. The results of an analysis of variance are most appreciably summarised in the form of a half-normal plot (see Figure 5). In these plots, the distance between points and the insignificance line indicates the level of significance. If a point lies on or close to the insignificance line then the factor or interaction can be categorised as insignificant. With this in mind, the hypothetical half-normal plot presented in Figure 5 shows that the main effects of factors A and C are significant, as well as that of the interaction BC. One of the most advantageous benefits of factorial DOEs is the identification of interactions. In complex study areas, the factors being varied may interact with each other, and therefore simply assessing the main effects can be misleading. To better understand how interactions affect the measured outcome, interaction effect plots (see Figure 6) can be generated following an analysis of variance. An interaction effect plot presents the average measured outcome on the y-axis, the varied levels of one of the factors making up the interaction on the x-axis, and individual lines for each level of the other factor. When interpreting one of these plots, it is important to consider the difference in gradient of the interaction lines. The greater the difference in line gradient, the greater the strength of the interaction. With this in mind, Figure 6 reveals a considerable interaction to exist between factors B and C. In this case, it can be seen that the effects of factor B are more significant at higher levels of factor C (indicated by the steeper gradient of the C+ line).

Figure 8. Annotated Diagrams of the Unidirectional Roller Test Rig

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The design ultimately chosen for the initial stages of experimentation in this research case was a 26-1 fractional factorial design of experiment. This design was particularly favourable in that it allowed for

BELTCON 20 the effects of a large number of belt conveying factors to be investigated with a manageable set of 32 factor screening experiments. Following the completion of the experiments, this factor screening exercise allowed for subsequent focused experimental programmes to be designed that were able to explore more significant factors in greater depth.

Experimentation Research methods

In order to determine which belt conveying factors have the greatest impact on unidirectional idler performance, a range of experiments was planned using DOE techniques. These experiments were executed using the Unidirectional Roller (UDR) Test Rig that was designed and constructed by various member companies of the CMA. The experiments conducted with this rig were designed to determine the resistive forces that develop between locked rolls (i.e. unable to rotate) and a conveyor belt being pulled over these rolls, to represent a belt slipping down an incline in the event of a belt snap.

The mechanism used to simulate a unidirectional roller and infer the resistive force between locked rolls and the belt is illustrated in Figure 7. It is important to note that conventional idler rolls were installed on the UDR Test Rig, not unidirectional idler rolls. These rolls were, however, secured to the rig in such a way as to imitate the functionality of unidirectional rolls. This was achieved through the use of a rigid connection between the idler roll face and the fixed cantilever load cell. From Figure 7 it can be seen that the induced force (F) measured by the load cell at an eccentric distance (e) from the roll axis was used to determine the rotation resisting torque (τ) according to: Since the forces are in equilibrium just before the belt slips, the opposite oriented resistive torque acting at the belt-roll interface (τres=Fres r) has the same magnitude as the measured torque (τ). Therefore load cell measurements were used to calculate resistive slip forces at the belt-roll interface according to:

Unidirectional roller test rig

The UDR Test Rig consisted of a steel frame onto which idler sets, sheave wheels, winches and a belt tensioning frame were fitted (Figure 8.a). A ten-metre length of conveyor belting, troughed to the same degree along its entire length, was tensioned over the idlers with cables that were connected to both ends of the belt via clamps attached to trolleys. These cables were guided by four sheave wheels to the bottom of the rig where they were connected to the tensioning frame. This frame used a six-tonne lever hoist to provide the necessary belt tension, in the range of 5 to 25 kN, which was measured with a load cell (Figure 9). The belt pulling force was provided by a winch fixed to the rig which pulled the tensioning frame along steel rails. The rig could also be rotated through one of its ends, thus allowing tests to be run at inclinations between 0° and 15° in 5° increments (Figure 8.b). It is also important to note the mechanism used to simulate unidirectional rolls and measure slip forces, as shown in Figure 7, was installed onto the six rolls of the two idler sets in the centre of the rig.

Figure 9. Images of the UDR Test Rig and its Key Components

Besides varying the inclination angle, other important belt conveying parameter levels could also be changed with the rig. Troughing angle (0°, 35° and 45°), idler roll type (steel, Nylon and HDPE), idler roll diameter (127 and 152mm) and idler pitch (1200, 1500 and BULK HANDLING TODAY

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BELTCON 20 1800mm) were varied by attaching idlers to the steel frame at different spacings, with different troughing angled frames, installed with rollers of varying size and type. Different levels of belt sag could also be achieved by varying idler pitch, tensioning the belt at different levels and varying the material loading. The belt load was simulated through the use of sand bags (as shown in Figure 9).

Discussion of results

Before the results of the experimental programmes are presented, a typical example of the data collected during a UDR Test Rig experiment will be considered. Once all the test runs of a particular experiment had been conducted, a resistive force graph was plotted by averaging the force response data from all test iterations and across both of the measured idler sets. An example of the resulting resistive force plot is shown in Figure 10. From these graphs, the mean slip force for each experiment was determined using a MATLAB program which calculated the average slip force over an interval of three seconds, beginning at the user defined onset of kinematic slip.

Following the overall resistive force line shown in Figure 10, it may be seen that after the instance of initial belt pull (when time = 0), the average idler set resistive force first increases sharply together with the increasing belt pulling force. Then the force levels off briefly (inflection region) as a result of the belt-roll friction limit being reached. However, the belt does not start to slip at this point since there is still not enough belt pulling force to overcome the non-friction sources of slip resistance (such as belt sag). This is why the inflection region is immediately followed by an increase in the resistive force as a result of the remaining resistance inherent in the conveyor belt which needs to be pulled up and over the locked idlers. This period of increasing resistive force ends with a peak force value being reached (the static resistive force limit), at which point the belt begins to slip over the locked idlers. The resistive force seen to oscillate about a lower force value (the kinematic slip force) after the resistive peak is indicative of a typical slip-stick motion of the belt sliding over the locked rolls at a constant velocity.

Figure 10. Typical Averaged Resistive Force Graph (Experiment A26)

Factor screening experimental results

In order to determine which factors and combinations of factors contribute most significantly to the resistive force developed at the contact between the belt and a locked idler roll, a factor screening experimental study was conducted. As mentioned earlier, the chosen DOE was a 26-1 fractional factorial design requiring a total of 32 experiments. This series of factor screening tests involved two extreme values for each parameter, a high value and a low value, and was used to determine the kinematic belt slip force that results from varying inclination angle (0o and 15o), idler pitch (1200 and 1800mm), roll material type (either nylon or steel), roll diameter (127 and 152mm), troughing angle (0o and 45o) and belt tension (5 and 25 kN). The half-normal plot that was derived from this initial investigation (see Figure 11) shows idler pitch, troughing angle and belt tension to be the most consequential factors, while the interaction between pitch and trough, the roll type main effect and the interaction between roll type and diameter demonstrate a medium-to-low significance level.

Figure 11. Half Normal Plot for Experimental Programme A

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Considering the half-normal plot, the exceptional significance of idler pitch is particularly appreciable. This high level of consequence makes sense when considering the effect that idler

BELTCON 20 pitch has on belt friction and sag. The greater the pitch, the greater the loads being supported by each idler set will be (therefore resulting in greater frictional resistance according to Equation 1) and the greater the belt sag between successive idlers will be (thus requiring a greater downward pulling force do drag the belt up and over each idler set).

tension main effect may seem reasonable, its direction (see Figure 12) is a bit more difficult to understand. Numerically, the magnitude of the calculated main effect demonstrates the relative significance of the associated factor, while the sign indicates whether the effect increases or decreases when increasing the factor level.

Similarly to idler pitch, varying the troughing angle significantly affects slip resistance due to belt friction and sag. When a belt is bent into a trough, the elastic potential energy stored in the belt tries to push the belt flat again, thus resulting in significant normal forces (and therefore friction forces) acting at the wing rolls.

With this in mind, the main effects plot shows belt tension to have a positive effect on belt slip; meaning that an increase in belt tension results in an increase in slip force. This contradicted with the initial expectation that an increase in belt tension would reduce the belt sag and thus result in a decrease in the non-friction element of slip resistance.

In terms of non-friction resistances, introducing a troughed belt profile results in a type of three-dimensional belt sag when the belt trough opens up slightly between successive idler sets. This means that in order for the conveyor belt to slip down the incline, the gravitational pull of the belt needs to be sufficient enough to flex the sides of the conveyor belt to the troughing profile at the idler sets.

Insights

Additionally, if the belt is loaded with material, the belt has to compress the material in order to pass the idler rolls. Figure 11 reveals belt tension to be the next greatest contributor to slip resistance. Although the magnitude of the belt

At this point it is worth clarifying why tension was varied at all in the various experiments conducted. Low and high tension states were explored in order to determine which tension state is better from a resistance to belt slip point of view. This therefore enabled sufficient insights into the low/ no tension case (that would be expected when a belt snap occurs) to be able to state whether the belt will be likely to run away or not. With this in mind, it would appear from Figure 12 that when the conveyor belt is empty, the worst belt tension case is that when tension is low. In addition to the identification of significant factors, it is also interesting to note which factors were deemed to have little or no significance. Inspecting the half-normal plot in Figure 11, it may be seen that inclination angle has no effect on belt slip. This is because the test rig was designed to force belt slip. Many of the experiments conducted were set up with operating conditions that would never otherwise have experienced slip (such as the horizontal belt case). Despite this, slip was achieved every time by increasing the pulling force until the belt began to move.

Figure 12. Main Effects Plot for Experimental Programme A

As such, the inclination effect could not be deduced from the factor screening study, but was further explored in a series of additional experimental programmes.

Figure 13. Slip Forces Grouped According to Tension, Pitch and Trough (Programme A)

Finally, although idler roll type was observed to be a significant factor, its significance relative to the other factors was found to be lower than anticipated. It was expected that the roll type would contribute more seriously to the braking of the locked rolls because of the effect that roll material has on friction.

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BELTCON 20

Upon closer inspection, it was deduced that the range of coefficients of friction (COF) tested using nylon and steel rolls (0.3 and 0.4 respectively) was fairly small. In addition, the lower than expected significance of roll type indicates the contribution of non-friction resistances (such as belt indentation and sag) to the overall unidirectional idler resistive force. To gain further insight into the effects of this parameter, HDPE rolls (which exhibit a much lower COF) were incorporated into the experiments of subsequent programmes.

Overall trends

The overall trends of the factor screening experiments may now be summarised. These are presented in the slip force column chart below (Figure 13). It should be noted that in this figure, lower values are indicative of earlier belt slip, and are therefore of concern in the context of this research. Figure 14. Schematic Diagram of the Experimental Programmes Conducted

Figure 15. Half Normal Plot for Experimental Programme D

From this graph it may be seen that an increase in pitch, trough or tension results in an increase in the resistive force developed at a locked idler set. For any particular combination of these three factors, the variation in inclination angle, roll diameter and roll material have little influence on the measured slip force. This figure also shows that the worst inclined belt case in terms of unidirectional idler braking performance (i.e. the one resulting in the lowest resistive force at belt slip) is that where the idler pitch is the lowest (1200mm), there is no troughing of the belt and the system tension is low. Conversely to this, the best case scenario is seen to be when the idler pitch is the highest (1 800mm), the belt is troughed to 45o and belt tension is high.

Focused doe test results

Based on the results of the factor screening experimental programme, a series of additional experiments was conducted in order to develop a better understanding of how the various factors affect unidirectional idler performance. A summary of the supplementary experiments conducted may be seen in the flow chart presented in Figure 14. Figure 16. Significant Interaction Effect Plots for Experimental Programme D

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In addition to the development of a

BELTCON 20 better understanding of unidirectional idlers, the experiments presented in Figure 14 also allowed for a larger data set to be compiled and used to develop a unidirectional idler quantity specification model (as seen at the end of this paper). The first of the supplementary experiments conducted, Programme B, was designed to gain further insights into the

effect of idler roll material. From this study it was found that a significantly lower force was required to pull the belt over locked HDPE rolls as compared to steel and nylon. The next study conducted, Programme C, was used to test whether or not the inclination angle of the test rig had any significant impact on the measured slip force. Ultimately, very little difference in measured slip force was observed with increasing angles of inclination, thus confirming the insignificance of inclination angle. This discovery allowed the majority of future experiments to be conducted with the test rig in the horizontal position.

Figure 17. Three-Dimensional Surface of Tension Averaged Kinematic Slip Forces

Experimental Programme D was designed to incorporate â&#x20AC;&#x153;paintlessâ&#x20AC;? steel rolls into the investigation, where the paint was removed from the rolls and the surfaces polished. This was done to mimic the realistic surface condition of steel rolls, which are likely to lose their paint layers quite quickly when in operation. In addition, this programme introduced the factor of belt loading for the first time. Using the data collected from this study, a half-normal plot was generated in order to reassess the significance of belt tension, idler pitch, idler roll type, material load and troughing angle. The resulting plot is presented in Figure 15 and reveals the three significant main effects to be material load, troughing angle and idler pitch, and the significant interactions to be those between material load and troughing angle, and between material load and idler pitch.

Main factors

Figure 18. Free Body Diagram of an Inclined Conveyor Belt

Figure 19. Diagram of the Friction Coefficient Measurement Technique

In terms of the main factor effects, Figure 15 reveals material load to have by far the most significant influence on unidirectional idler performance. This is because the introduction of material load onto the belt greatly affects the magnitude of supporting normal loads at each of the idler rolls, thus increasing the frictional braking potential according to the friction equation (F=ÎźN). In addition, a loaded belt experiences considerably more sag than an unloaded one. Consequently, greater effort BULK HANDLING TODAY

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BELTCON 20 is required to pull the loaded belt up and over each idler set. With regards to the second and third most significant main factors (trough and pitch), it is interesting to note that although these factors were also identified as significant in the factor screening study (Figure 11), the order of their significance differs between the two studies. In this case, troughing angle demonstrates greater significance than idler pitch. This is because of the strong interaction between belt load and trough (see Figure 15). This is better understood with reference to the interaction plot presented in Figure 16a. In this figure, the notable difference in effect line gradient emphasises the strength of the interaction between load and trough. The $+ and $- lines show that adding material to an empty belt has greater influence on slip when troughed belts ($+) are used as opposed to flat belts ($-). This is interpreted from the steeper $ + line and may be explained by considering how a fully loaded troughed belt would demonstrate a much greater mass per metre than that of a fully loaded flat belt. This heavier loading condition results in higher slip impeding belt sag and friction. Keeping the focus on interaction effects, the relationship

between material load and idler pitch may be explained. The effect plot of this two-factor interaction (Figure 16b) shows that material load has a greater effect on belt slip when larger idler pitches are used (as indicated by the steeper "+ effect line). This is because the increase in slip restricting belt sag that results from adding material load to a belt is further intensified when the horizontal distances between successive idler sets are larger. Following on from this, Experimental Programme E was designed and conducted to expand on the three most significant factors as identified through the analysis of the factor screening experiments (i.e. pitch, trough and tension). In the case of the first experimental programme, each factor was varied about two levels (low and high), whereas in Programme E, medium levels of idler pitch, troughing angle and belt tension were added. The belt slip trends observed throughout this study are summarised by the kinetic slip force surface presented in Figure 17.

Slip forces

This three-dimensional graph illustrates the best and worst empty belt set up scenarios in terms of resulting belt slip. It is important to reiterate that in the context of this paper; a low slip force is not desirable as it represents a situation of potential runaway in the event of a belt snap. It is therefore preferable to maximise slip forces when possible.

Figure 20. Predicted vs Actual Resistance Factors based on Minimum Values of Îť

With this in mind, Figure 17 reveals the best case to be when idler pitch and troughing angle are at their highest (1 800mm and 45o respectively), and the worst case to be when the idler pitch is 1 200mm and the belt troughing angle is 45o. These findings make sense when considering that a lower idler pitch results in lower belt supporting normal forces which ultimately lowers the slip resisting friction forces at the idler roll-belt interface. Conversely to this, the larger idler pitch results in higher normal and friction forces at the locked idler rolls. In terms of troughing angle, it is interesting to note that both best and worst empty belt slip cases were observed when the troughing angle was set to its maximum level of 45o.

Figure 21. Comparison of Quantity Prediction Models for Common Operating Conditions

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Although it was expected to observe the maximum slip force when the troughing angle was maximised, it was not expected to observe the minimum slip force at this level of belt trough as well. A possible reason for this may be in the way that

BELTCON 20 idler pitch and belt trough interact with each other. Recall from the factor screening experiments that the most significant two-factor interaction was that between idler pitch and troughing angle. When the idler pitch is small, not only are the effects of belt friction lower, but the non-friction effect of belt sag is lower – including three-dimensional sag. When the belt is troughed to 45o and the idler pitch is minimised, not only is there lower three-dimensional sag due to the short distances between idler sets, but there is also likely to be less conventional sag as a result of the greater degree of longitudinal belt stiffness gained through the curved profile of a troughed belt.

Five additional programmes

Following this, five additional programmes were conducted (as seen in Figure 14). The purpose of these experiments was to gain further insight into the effects of belt loading, idler roll material construction, the interaction between inclination angle and belt load, and the previously understudied medium troughing angle level of 35o. In addition to the increased functional understanding gained from running these focused experiments, the collection of more slip force observations allowed for a larger data set to be established and then drawn from when deriving and training the unidirectional idler quantity specifying numerical model. Some of the key findings from the remaining experiments are listed below: • The results of Programmes F and G reiterated the findings of previous experimentation – that slip force increases with increasing idler pitch, material load and troughing angle, and that HDPE rollers result in noticeably lower slip forces when compared to other roll materials. • Programmes H and I showed that when an inclined belt is loaded, the material on the belt introduces an additional downward pulling force which causes a slight reduction in the critical slip force. • The analysis of substituted and repeated experiments showed that belt wear, which develops over time, affects the critical slip force. An increase in belt wear results in a lower observed resistive force at belt slip (i.e. belt wear is detrimental to unidirectional idler performance).

Specifying the required quantity of unidirectional idlers Preliminary analysis of the mechanics of unidirectional idlers

In order to use the experimental findings to determine what quantities of unidirectional idlers are required for any given conveyor belt set-up, it was important to develop a better understanding of the mechanics of the system. Initially, this was done by conducting a basic force analysis (see Figure 18) and deriving a simplified unidirectional idler quantity formula.

Figure 18 illustrates the simple mechanics of a length of belt (L), at a specific angle of inclination (α), supported by idlers separated from each other by a constant pitch (a). It is important to note that in this figure, the conveyor belt is assumed to be a rigid straight body and the resistive force is assumed to be as a result of belt-idler contact friction alone.

where η is the required fraction of idlers that need to be unidirectional to prevent slip, g is the acceleration due to gravity (taken as 9.79 m/s²), N is the normal force of the idler roll supporting the conveyor belt, qb is the mass per metre of the belt and qm is the mass per metre of the material load. Assuming that the material load is distributed evenly along the entire length of the conveyor belt, Equation 5 can be substituted into Equation 4 and the unidirectional idler quantity formula for this preliminary Friction Model can be stated as: Friction Model:

Additional friction study

During the course of experimentation, it was discovered that the friction between locked idler rolls and the conveyor belt was not the only source of resistance to belt slip. Thus, the need to isolate the friction force from the overall resistance measured became apparent. In order to do this, a friction study was conducted in the TUNRA Bulk Solids Africa (TBSA) Laboratory, located at Wits University. The experiments that were run in this lab were adapted from the standardised wall friction testing method by clamping belt samples to a shear tester and pushing loaded material samples along the belt (Figure 19). This allowed for the determination of friction coefficients (μ). This friction study examined four different belt samples tested against the three most common idler roll materials: steel, nylon and HDPE. A total of 25 experiments were conducted to measure the COF. This study revealed COF to be slightly pressure dependant, with lower contact pressures usually resulting in lower COFs. The results also showed HDPE and steel samples to yield the lowest and highest COFs respectively. From the conducted experiments, the worst case (i.e. lowest COF) for each roll material sample was identified. With the slight pressure dependence of friction in mind, these worst case values were calculated using a contact pressure of 15 kPa – corresponding to a 900 mm wide, 15 kg/m conveyor belt supported by Ø152 mm idler rolls separated by a pitch of 1.2 m and demonstrating a roller wrap angle of 10°. The COFs relating to this pressure state (see Table 1) were ultimately used to calculate non-friction coefficients (explained in the next section) for each of the experiments conducted using the UDR test rig.

Quantity formula derivation

Since it was determined that the force resisting belt motion over locked idler rolls is not entirely due to friction, the conventional friction formula (Ff = μN) could not be used to determine the resistive force acting at the belt-idler interface. However, using a modified version of this formula, the overall resistance force could be related to the roll normal force. This adapted formula is given by:

Knowing the system to be static, the force balances relating to this free body diagram can be stated as follows: Table 1. Minimum Observed Coefficients of Friction (μ) at 15 kPa of Contact Pressure

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BELTCON 20 where Fres is the resistive force and ψ is the resistance coefficient given by the product of the friction and non-friction coefficients (μ and λ respectively). The conventional friction formula was adapted by replacing the friction term with a newly defined resistance coefficient. This coefficient can be broken up into friction and non-friction coefficients, which contribute to overall slip resistance. With the minimum recorded friction coefficients known (see Table 1) and the resistance coefficients determined from the measured slip forces and estimated loading conditions for each experiment (ψ=Fres/N), the non-friction coefficient for each experiment was determined using: The use of these empirically determined non-friction factors (λ) together with the measured COFs, allowed for the resistive force developed at a unidirectional idler set to be found, and for a table of non-friction factors at different operating conditions to be drawn up (see Table 2). In order to extend the empirical findings to the theoretical case, the equations for normal force acting at the unidirectional centre (Nc) and wing (Nw) rolls are given by the following two equations [10].

where:

in order to prevent slip based on the centre and wing roll resistance coefficients (ψc and ψw respectively), and η is the total percentage of idler rolls that need to be unidirectional in order to prevent slip.

Numerical model results

With all resistive and friction coefficients known for each measured belt slip force and knowing the relationship between these two factors (see Equation 8), the non-friction coefficients (λ) were calculated for each experiment. These factors were then condensed into a list of the minimum recorded values corresponding to the varied levels of the three most significant belt conveying factors (belt load, idler pitch and troughing angle). The resulting non-friction coefficients (calculated for centre rolls, wing rolls and idler sets) are summarised in Tables 2 to 4. The non-friction coefficients listed in these tables were then used together with Equation 8 and the minimum observed coefficients of friction to predict the centre roll, wing roll and overall idler set resistance coefficients (ψc, ψw and ψ) for each experimental set-up. These predictions were then plotted together with the actual resistance factors determined through experimentation. An example of one of these comparison plots (in this case the one for overall idler set resistance coefficient) is shown in Figure 20. This graph consists of a scatter plot of all the experimentally determined resistance coefficients re-ordered according to the ascending order of the resistance coefficient prediction model.

Prediction line In the above equations, l1 is the idler roll face length (m), B is the belt width (m), ρ is the bulk density of the material being conveyed (kg/m³), Ac and Aw are the cross-sectional areas of the conveyed material directly above the centre and wing idler rolls respectively, and ω is the normal coefficient. These normal coefficients apply to the wing rolls of troughed belts that experience greater normal forces than as a result of gravity acting alone. Based on the preliminary mechanical model presented in Section 4.1, a more in-depth analysis was conducted, and a unidirectional idler quantity model was derived. This model incorporated the different resistive conditions of the centre and wing rolls resulting from their distinct normal forces (see Equations 9 and 10). In addition to this, considering the significant difference in resistive force at centre rolls as compared to the wing rolls, the model stipulates centre rolls as unidirectional first and only when the required quantity of these exceeds 100% are unidirectional wing rolls designated. The corresponding formulae of this model (the Resistance Model [10]) are given by:

Resistance Model:

where ηc and ηw are the required fractions of centre and wing idler rolls respectively that need to be unidirectional

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Figure 20 presents a comparison between the predicted and actual coefficients of resistances (y-axis) for all the experiments conducted on the UDR Test Rig (x-axis). This figure illustrates the relationship between the measured slip forces and the derived prediction model – the prediction line is seen to intersect the minimum resistance coefficients corresponding to the eight significant operating conditions (see Tables 2-4). Knowing that lower coefficients of resistance are detrimental to the functionality of unidirectional idlers, Figure 20 shows that the prediction method used is rather conservative – predicting coefficients that are never higher than actual values (especially if a safety factor is used). In summary, the above figure shows that if the Resistance Model is used to predict the resistance coefficient of a particular inclined belt operating scenario, the model will always err on the side of caution and use the worst observed case as the datum for predicting required quantities of unidirectional idlers.

Comparison study

Considering the derived Resistance Model, as well as the preliminary Friction Model presented earlier, a comparison study was conducted for a wide variety of inclined belt operating conditions. The comparison of these unidirectional idler quantity specifying methods was achieved with a numerical program that was designed to cycle through various levels of key conveyor belt factors and calculate the unidirectional idler quantities according to the different model equations. The various factors and corresponding factor levels cycled through this program are summarised in Table 5. A total of 3 240 different belt conveying scenarios were considered by varying these factors at all levels. The factors chosen to be varied in this case were all those that have a direct effect on the resistance coefficients and normal loads, as well as the principal factor of inclination angle.

BELTCON 20 Although this original study assessed a wide range of inclined belt operating conditions, many of the scenarios considered are very unlikely to occur in reality. The two factors that this particularly applies to are troughing angle and idler roll type. It is uncommon to design inclined conveyor belts without at least some degree of troughing (i.e. flat belts are unexpected). It is also rare to find inclined belts installed with HDPE rolls; steel being the gold standard. With this in mind, the more common operating conditions were applied to the numerical simulation. The results of this condensed study, which only considered steel rolls and troughing angles larger than 30°, are shown in Figure 21. This figure illustrates the quantity predictions relating to the derived Resistance Model together with the preliminary Friction Model, grouped according to belt inclination and arranged in ascending order of the required quantity of unidirectional idlers. It should be noted that when calculating the required quantities of steel unidirectional rolls, the worst-case coefficient of friction corresponding to a worn roll, without any paint on its surface, was used (i.e. μ=0.27). It should also be noted that a safety factor of 1.15 was used for both models.

Inclination angle

In the model comparison plot presented in Figure 21, the required quantity of unidirectional steel rolls as specified by the Friction Model is seen to depend on inclination angle alone and is not affected by the idler pitch, belt trough, belt width or material load. This is in accordance with the model Equation 6. The quantity of these safety devices according to the Resistance Model, on the other hand, is seen to change with changing levels of inclination angle as well as with idler pitch, troughing angle, belt width and material loading conditions. With reference to the Resistance Model, it is also interesting to note the spike in required unidirectional idler quantities that occurs when the conveyor belt is empty. This is because an empty belt does not experience as much resistance from belt sag or belt cover indentation as one that is loaded with material. In addition, the increase in COF experienced with increased contact pressure, means that loaded belts exhibit additional resistance to belt slip as a result of contact friction. One of the important conclusions that can be drawn from this observation is that an empty conveyor belt constitutes a worst-case scenario in terms of belt slip resistance. When specifying the required quantity of unidirectional idlers for an installation, the calculations must be done for an empty belt, not a loaded one. If an inclined conveyor belt system has enough unidirectional idlers to prevent the runaway of an empty belt then it will also be able to hold the belt in place when loaded with bulk material.

Quantities

Comparing the two models presented in Figure 21 it may be seen that the Resistance Model derived from the experimentally determined friction and non-friction factors almost always specifies lower quantities of unidirectional idlers than the preliminary Friction Model. In fact, only at an inclination angle of 18° does the Resistance model begin to specify larger quantities for certain combinations of inclined belt parameters (when the belt is empty and the idler pitch and troughing angle are minimised). Knowing the Resistance Model to already be very conservative in its estimation of required unidirectional idler quantities, the comparison plot presented in Figure 21

shows the Friction Model to be somewhat wasteful – particularly in operating conditions that exhibit a high degree of conventional and three-dimensional belt sag (i.e. when the idler pitch and/or troughing angle is large).

Matrix

Finally, it was desired to condense all the findings down into a compact quantity matrix that may be used in industry as an initial approximate quantity specifying tool. This matrix was generated by using the Resistance Model formulae to calculate the quantity of centre and wing rolls required to be unidirectional at varying angles of inclination for a worst-case scenario. This being an empty conveyor belt troughed at 45° and supported by idlers separated by a 1.2 m pitch. The combination of a 1.2 m idler pitch and a 45° troughing angle constitutes a worst case scenario because of the very low non-friction coefficient that results from this particular pairing (see Tables 3 and 4). The results of this exercise, which was conducted for both steel and HDPE rolls, and which used a safety factor of 1.15, are presented in Table 6. This table shows that it is unsafe to use steel unidirectional idlers for conveyor belts inclined at an angle greater than 21° and it is unsafe to use HDPE unidirectional idlers for inclines greater than 16°. Knowing that inclination angles greater than 18° are uncommon in practice, it is justified to assume steel unidirectional idlers to be suitable runaway preventing safety devices regardless of operating conditions. Unidirectional HDPE rolls, on the other hand, should be used with caution.

Conclusion

The following lists the key findings of unidirectional idler experiments as well as the numerical simulation: • The conveyor belt experiences belt slip at the wing rolls before the centre roll. Therefore, centre rolls should be prioritised when specifying the required quantity of unidirectional idler rolls. • The friction developed between a locked idler roll and the belt is not the only source of resistance affecting the performance of unidirectional idlers. Instead, there are non-friction resistances at play (such as belt sag) that strongly influence the belt pulling force required to induce slip. • High Density Polyethylene (HDPE) rolls perform poorly when converted to unidirectional idlers, exhibiting low resistive forces at belt slip. This is because of the lower COF of HDPE when compared to nylon and steel rolls. • The smoothing of steel idler rolls (resulting from the painted surface wearing away during operation) has a slight effect on the magnitude of the friction developed at the surface of these rolls, but ultimately has no significant influence on unidirectional idler performance. • The most significant inclined belt conveying factors (in terms of their effect on kinematic slip force) are material load, troughing angle and idler pitch – with material load having by far the most influence. Increasing the levels of these factors results in increased resistive forces at belt slip. • The worst unidirectional idler performance case exists when HDPE idler rolls are used, when the idler pitch is low (1 200 mm), the troughing angle is high (450) and the belt is empty. • A conservative method for specifying the required quantity of unidirectional idler rolls was derived through the BULK HANDLING TODAY

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BELTCON 20

Appendix

separation of friction and non-friction effects and the use of experimental data collected with the UDR test rig. • This method took inclination angle, idler type, idler pitch, troughing angle and loading conditions into account whereas the preliminary friction method only considered inclination angle and idler type. • Contact friction between an idler roll and a conveyor belt exhibits a slightly positive pressure dependence – friction coefficient increases with pressure.

Table 2. Minimum Non-Friction Factor Matrix

• An empty conveyor belt constitutes a worst-case scenario in terms of belt slip resistance. When specifying the required quantity of unidirectional idlers, the calculations must be done for an empty belt, not a loaded one. • It is not advisable to specify HDPE and steel unidirectional idler rolls for inclination angles greater than 16° and 21° respectively.

Table 3. Minimum Non-Friction Factor Values for Locked Centre Rolls

Table 4. Minimum Non-Friction Factor Values for Locked Wing Rolls

Table 5. Factors Cycled Through the Numerical Simulation

This paper was first presented at the Beltcon Conference in 2019. Copyright is vested with IMHC. www.beltcon.org.za Bryan Moore Data Analyst Business Science Corporation Tel: 072-445-3701 Email: bmoore@bscglobal.com Terrance Frangakis Senior lecturer School of Mechanical, Industrial and Aeronautical Engineering University of the Witwatersrand P/Bag X3, WITS, 2050, South Africa Tel: (011) 717-7333 Email: Terrance.Frangakis@ wits.ac.za

Table 6. Worst Case Unidirectional Idler Quantities Required at Various Inclination Angles

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MARKET FORUM

Cost and installation time analysis When Diesel Power International Services’ subsidiary, based in Namibia, needed advice on what cranes and hoists could be applied effectively to their newly designed work space, that would house their assembly lines and diesel engine stripping facilities, they called in Konecranes from Cape Town to assist. Installation and delivery times were tight, but the innovative solution that resulted from a Cost and Installation Time Analysis conducted by Konecranes sealed the turnkey deal. “The project was for a semi-free-standing gantry with 1 x 3.5ton single girder crane and 2 x 500kg column mount jib cranes and hoists” says Markus Labuschagne, Konecranes’s Regional Branch Manager who is based in Cape Town.

“The equipment specifications that the customer had originally requested - one 3.5ton jib crane and two 500kg jib cranes - would have worked out at a higher costing and not enhanced the layout of the proposed floor area. Additionally, our cranes have enabled the customer to place items on the new mezzanine level in the production plant,” he explains. The 3.5ton crane will be used for the lifting, stripping and assembly of truck diesel engines while the 2 x 500kg column mount jibs will be used for serving two work stations where smaller components and parts are repaired and serviced. Markus continues, “As a result of our Cost and Installation Time Analysis it was our recommendation that the alternate cranes we identified as suitable for their project, would cover a greater area than the equipment originally specified, and would offer greater benefits to Diesel Power International Services. This plus the fact that we were able to deliver the equipment to the customer in Namibia within their stated timeframe. “The other benefit as a result of our analysis was that the equipment we recommended required less excavation work inside of the customer’s workshop, less disruption to their operations and the total site work period was reduced, along with a nearly 40% cost reduction. Safety standards and safe operator conditions are not negotiable and the new installation most certainly is safety compliant,” he concludes. Konecranes Markus Labuschagne Email: markus.labuschagne@konecranes.com

Exceptional warranties and performance Kemach has launched their new range of forklifts for the South African and Sub Saharan African markets, which will be promoted under their newly-formed Kemach Forklifts division.

aftermarket suppliers for battery and charger supplies, forklift attachments and management systems. Driver training and monitoring through Kemach’s forklift management system is also available.

Frans van den Heever, General Manager for Kemach Forklifts says, “We are delighted to announce the Kemach Forklift range, in partnership with Anhui Heli, which we believe will complement our existing quality earthmoving products. This range offers our customers a South African forklift warranty first - a five year/12 000hr warranty on the complete machine, not just parts of the machine”.

Kemach Equipment Tel: (011) 826-6710 Sales enquiries Chantellec@kemach.co.za Service enquiries Deanv@kemach.co.za

The forklifts have specified Japanese engines, Heli built ZF transmissions and robotically manufactured chassis, ensuring premium brand quality at very competitive pricing. “The range comprises a walk-behind powered pallet jack right through to 45ton container handling units, enabling us to compete in all sectors of the market. We have a national footprint of 11 branches and eight sub-dealers across South Africa, giving us the biggest footprint in the materials handling industry when it comes to service-ability and guaranteeing uptime for our customers,” Frans concludes. The forklifts will offer customers the lowest cost of ownership over the lifetime of the machine due to their reliability and competitive pricing. Local support features include BULK HANDLING TODAY

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Seamless energy and data supply The SR-Express range from Powermite, which forms part of Conductix-Wampfler’s global SR series of spring cable reels, is engineered to meet the energy and data supply requirements of moving machinery including overhead bridge cranes, gantries, mobile tables, aerial ladders, lifts, elevators and elevated work platforms. “Superior product quality is fundamental to reliable performance which in turn drives machine and plant uptime and ultimately, productivity and profitability,” says Jacques van Rooyen, Managing Director of Powermite. “Consequently it is our responsibility to supply our customers with world-class products that will perform efficiently over a long life cycle and minimise Opex to deliver lowest total cost of ownership.” The SR-Express (SR10-SR60) range combines the best qualities of Conductix-Wampfler’s cable reels. All components, from the cables and cable drum to the slip rings, springs and mounting flange, are manufactured from the best and most durable materials to ensure optimum operational efficiency over a long life cycle. Smart engineering ensures that the SR-Express spring cable reels are ready for use and facilitate maintenance to minimise costs and maximise uptime. As the product is supplied with the cable already installed and connected to the slip rings, it is a simple matter of plug-and-play. Featuring winding diameters from 170mm to 400mm, the cable drum is fitted with

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sealed ball bearings and is lubricated for life. The cable drum body and flanks are manufactured from robust zinc-plated steel; for operator safety, the flank edge has been designed to optimise cable arrangement during winding. The halogenfree PUR (polyurethane) cables, specifically designed for reeling applications, provide excellent wear resistance and high flexibility. Powermite (a division of Hudaco Trading (Pty) Ltd) Tel: (011) 271-0000 www.powermite.co.za

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Meeting production deadlines Demag, one of the largest suppliers of cranes in South Africa, recently supplied a 10-ton V-Girder crane to a local copper coil factory. The crane was a new production crane which was installed into an existing production bay. “Prior to recommending the V-Girder product, we conducted wheel loading comparisons for the company. The results showed that the lower wheel loadings of the V-Girder crane meant that no changes were required to the existing supporting gantry structure, thereby offering a substantial cost saving. Additionally, the V-Girder crane is 17% lighter than conventional box girder cranes” says Richard Roughly, Manager for Industrial Equipment Sales, at Demag. He adds, “The V-Girder crane offers benefits such as greater efficiency (as the oscillation of the crane girder dampens 30% faster than a conventional crane) resulting in an increased load handling rate. The 10-ton crane has a 17.5 metre span with a lifting height of 6 metres. The unique design of the V-Girder will also allow more light into the factory, creating a safer and better lit environment for technicians to operate in.

"The V-Girder has double the structural design life compared with a conventional crane performing similar functions” While Demag is renowned for its competitiveness combined with high level of technical expertise, critical factors for this client in selecting the V-Girder also included the guarantee of delivery. Initial discussions enabled Demag to correctly assess the required technical specifications and manage the critical six-week delivery timeframe. “We believe the technical advantages of the V-Girder crane coupled with availability of crane sets, enabled us to meet the fast turnaround time from order to delivery that the client required. The importance of availability is often overlooked, but it does play a major role when production outputs are dependent on new equipment being installed within the required production window,” Richard concludes. Demag Richard Roughly, Senior Manager, Sales & Marketing MH Tel: (011) 897-8123, Email: Richard.Roughly@demagcranes.com

More accommodating The growing popularity of the Mato Products’ expanded offering has led the company to boost its service and repair facilities. Andrew Frank, operations manager at Mato Products, highlights the recent completion of the new spray-painting booth, which has doubled the firm’s capacity to finish refurbished items. Well known as a leader in conveyor belt lacing, the Multotec subsidiary also offers a range of belt cleaning solutions. “To keep up with market demand, we have expanded our spray booth significantly in terms of size and throughput capability,”

says Andrew. “It can now accommodate components up to a length of 2,2 metres and provides a more productive environment for operators.” This now allows for all repair and finishing work, even on the longer diagonal belt cleaners, to be spray-painted in-house, he adds. Importantly, this improves turnaround time, quality control and cost to customer. Multotec www.multotec.com

Andrew Frank, operations manager at Mato Products.

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Mining partnership for Africa Mining industry equipment supply company Austin Engineering, suppliers of customised equipment to large global mining clients, mining contractors and original equipment manufacturers, and ETT, manufacturers of open pit mine support equipment and specialised mobile industrial equipment, have signed the beginning of a partnership agreement which sees them jointly marketing, selling and supporting their products through one company across Africa. The joining of the two southern hemisphere industry mining equipment powerhouses follows months of discussion and planning to ensure that customers serviced by both companies remain the focus and that product quality and after sales service support are stronger than ever. The dispensing systems of ETT’s 100 Series Diesel Lube Truck are configured to Austin Engineering, an Australian Stock customers’ needs and are capable of filling three vehicles simultaneously. Exchange listed company with headquarters ETT is a leader in the field of innovation, design and manuin Brisbane, has more than 50 years’ global experience in facturing of specialised mobile support equipment for mining engineering and manufacturing equipment for the mining and industry. The company has a proven record of providing industry with operations in Australia, Asia, North and South solutions to improve productivity and safety in mining and America, and now South Africa. industrial operations with its range of rear loading mining ETT, a privately owned South African company based in lowbed trailers, mining water trucks, fuel and lube trucks. Richards Bay, with product already distributed in more than ETT 20 countries around the world, celebrates 25 years of engi- Tel: (035) 751-1630 neering excellence this year. Email: sales@ett.com, https://ett.com/

Long-term rental Sumitomo Rubber Industries, a leading global tyre manufacturer, has taken delivery of 43 pieces of materials handling equipment on a 60-month rental facility from Goscor Lift Truck Company (GLTC). The machines have been deployed to work at Sumitomo’s world class manufacturing plant in Ladysmith, KwaZulu Natal. The fleet comprises 15 DEC 5-tonne electric tow tractors recently introduced to the local market by GLTC, 20 Doosan diesel forklifts with capacities from 1,8 to 7 t and eight Crown ESR5620-2.0 reach trucks with 11,5m lift heights. Jogen Moodley, Associate Manager Procurement at Sumitomo Rubber Industries, says the DEC electric tow tractors are deployed to transport work-in-progress material used for tyre production within the factory. He says the machines are powerful and smaller, and fit the bill for the factory’s confined working spaces. “Space constraints have created a challenge to move material within our factory. The DEC tow tractors can easily access confined

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spaces which cannot be accessed by conventional forklifts. Another key benefit is that these units use less gas or fuel, which in turn translates into both operational savings and fewer emissions, ensuring the health of our employees,” Jogen concludes. Goscor Tel: (011) 230-2600 Email: group@goscor.co.za www.goscor.co.za

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High security welded mesh

Pallisade

Gates

Gate Automation

Razor wire and more ....

What is High Security Weld Mesh HIGH Security Weld Mesh is wire fused and welded at a Horizontal distance of 76.2mm and a vertical distance of 12.7mm also known as 35B/3510 where 3 denotes 3”(distance between vertical wires), 5 denotes 0.5” (distance between horizontal wires), and B or 10 denotes gauge of wire

Salient Features • Difficult to Climb: The spaces between the Horizontal wires are too narrow for fingers to have grip • Impregnable: Extremely difficult to cut with a hand cutter as the beak of a wire cutter will not be able to penetrate the horizontal wires • Excellent Replacement option to Solid Wall as: 1. More economical than a solid wall 2. Faster to install than a solid wall 3. CCTV Camera has a clear view • Further upgrade possible with electric security system • Anti-corrosive & low maintenance

Standards

• Manufactured according to BS EN 10016-2 • Wire Sizes in accordance with BS EN 10218-2 • Tolerance on Mesh Size in accordance wiht EN 10223-7 • Tolerance on Panel Size in accordance with EN 10223-4 • Welding Strength in accordance with BS EN 1461 • Zinc Coating in accordance with EN 10245-1 • Anti Corrosion in accordance with BS En 3900 E4/F4

Tensile Strength • Wire has a tensile strenght of min 550 MPA

MARK: 083 454 6488

Email: mark@palifence.co.za

www.palifence.co.za

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Bulk Handling Today March/April 2020

Articles inside

Assessment of the Braking Performance of Unidirectional Idlers

TLB versus Compact Excavator

Preventing Reverse Rotation

Long and Bulky Loads

Solving Bottlenecks at Depth

When to Replace and When to Refurbish

Effective Gear Reducer

New Plant in Kitwe

From the Desk

Company Profile