Long detours may make the transport of raw materials from the mining area to the processing plant considerably more complicated and expensive than is perhaps necessary. However, local geography such as mountainous terrain, heavily populated areas or wide rivers interferes with smooth material flow.  At a cement plant in Sudan, a direct, straight link between the mining area and the processing plant seemed impossible to establish, but Doppelmayr’s RopeCon® made it possible.

To meet the daily demand of 9,000 t of limestone for Berber Cement Co’s new cement plant, a modern crushing plant has been installed 8 km away from the processing plant on the west of the River Nile.  Land transportation of 9,000 t/d encounters the massive natural obstacle of the Nile, which is some 850 m wide in this area. So transport of the material from west to east could only be achieved by building a bridge across the river, using small barges or by employing a ropewaytype system, crossing the river between two towers.

A study was commissioned to investigate whether RopeCon might be a suitable alternative. The system combines proven ropeway technology with the features of conventional belt conveyors. The continuous conveyor is elevated above the ground.  RopeCon easily crosses obstacles such as deep valleys, mountainous terrain, rivers, roads or other infrastructure, thus avoiding unnecessary detours and allowing for straight routes between loading and discharge points.

RopeCon consists of aatieber clutch flat belt with corrugated side walls. The belt may be fabric-reinforced or a steel cord belt, depending on the application. The corrugated side walls are cold-bonded or vulcanised onto the belt.  The individual belt sections are vulcanised together to form one continuous belt, just as a conventional belt conveyor.  The belt is fixed to steel axles arranged at regular intervals which support the belt.  Polyamide running wheels are fitted to either end of the axles. These wheel sets run on track ropes and provide positive belt guidance while preventing the belt from skewing. The combination of polyamide wheels on steel track ropes minimises rolling resistance and therefore energy requirements.

The galvanised, fully locked steel track ropes on which the wheel sets run are of the type used for suspension bridges or ropeways.  RopeCon uses three pairs of ropes: The bottom-most rope pair supports the bottom belt while the rope pair in the middle supports the top belt.  The upper-most rope pair gives additional stability to the structure and serves as the travelling rope for the inspection vehicle by means of which each point along the line can be accessed.  Track rope frames are fitted to the ropes at regular intervals to maintain the ropes in their relevant position and to distribute the loads.  The ropes have fixed anchoring at both ends and are guided over tower structures.

The belt is driven and returned by a drive drum in the head or tail station. After the material has been discharged, a turning device turns the belt by 180° to bring the soiled side of the belt upwards once more and to prevent residual material from falling off the bottom belt. The belt is turned once more before it runs onto the drum again in the loading station.  The drive system is similar to that of a conventional belt conveyor and consists of a gearbox and an electric motor.  RopeCon features two independent mechanical braking systems.  All braking actions are regulated to ensure constant deceleration and a

controlled stop under all circumstances.

Berber Cement’s loading station is located on the west shore of the river, immediately behind the crusher. Crushed stone arrives on trucks and is loaded via a feed conveyor and a chute. The RopeCon system crosses the Nile with a single large rope span between two tower structures positioned on either side of the river. It is not necessary to have a support structure in the river. The total length of the system is about 3,465 m from the loading station to the discharge station. Its transport capacity is 700 t/h.  There were other considerations for this solution, one of them being the space required by ground-based systems. In this desert country, the shores of the Nile form one narrow corridor of fertile land used for farming. A road would cut right through this valuable strip of land. RopeCon spans this corridor with minimal interference.

On the east shore, several settlements border the farm land. A transport solution relying on trucks would expose residents to considerable noise and dust. RopeCon avoids these problems and its low rolling resistance helps keep operating costs low, whereas the maintenance of an entire fleet of trucks as well as of a road would have resulted in considerable expense.  Virtually all RopeCon moving parts are mounted on the belt, which means that they keep travelling through the stations where they can be easily maintained. No complicated maintenance lines or platforms are required. Any inspections of the line can be performed with the inspection vehicle.

Minera Media Luna, a 100% owned subsidiary of Canadian Torex Gold Resources has developed its first gold mine in Mexico at its Morelos gold project. Doppelmayr was awarded a contract to build a RopeCon system for transporting the ore from the mine down to a stockpile in early 2013. The aerial continuous conveying system will transport the material at an hourly design capacity of 1,000 t through the steep and tough terrain from the crusher over a distance of 1.3 km. The RopCon system is suited to this project due to its low operational cost, with the system generating power due to the difference in height. Construction is scheduled to start for the summer of 2014 with commissioning planned for the winter of 2014/2015.

Beumer has established some equally spectacular conveyor systems (as the picture shows) and says that manufacturers that “not only supply everything from one source but also undertake the complete project to the point of turnkey handover are in demand. Beumer also acts as the main contractor on behalf of its customers. “A significant trend is that more and more clients want to commission their systems in a turnkey state,” says Dr Gerd Oberheuser, Head of System Technology at Beumer Group. “EPC or EPCM are the buzzwords here.”

With the acquisition of Enexco Teknologies India in 2011, the group has expanded its business activities in India and in doing so has strengthened its presence, particularly in the cement industry, in one of the world’s most important growth markets. Beumer system solutions, such as belt conveyors, are also in increasing demand in the coal industry.

“For a quotation to be accepted, contracts are often only placed on an EPC basis,” remarks Oberheuser. This means that, as well as supplying the equipment, Beumer is responsible for the whole process. This includes the design of the entire system, the installation, the commissioning and the instruction of subcontractors. Not only does a high availability of machines and systems play a decisive role, but also optimum support. For this reason, Beumer has set up competence centres in the Czech Republic, in Austria, at its headquarters in Beckum, and in North America. These take care of research and development, sales, project management and purchasing.

Beumer too points to the “considerable disadvantages” of trucks. “Road building is expensive, and the more raw materials have to be transported, the more journeys have to be made. Added to this are the operating costs and emissions caused by trucks – both with regard to fuel consumption and personnel costs as well as noise and dust.” A direct belt conveyor system route allows the material to be transported “much faster than by truck. Inaddition, belt conveyors can be operated with
significantly fewer personnel. Another aspect compared with trucks is the lower energy consumption, which at the same time reduces CO2 emissions. Depending on the project, belt conveying systems need up to 90% less primary energy than comparable truck transportation.”

Belt conveyors can overcome long distances, steep gradients and tight curves, and can be individually matched to the particular task and topography. Use is made of durable, tensionresistant conveyor belts. In doing so Beumer uses various calculation programs to determine the optimum belt design. These enable tensile forces to be analysed and also forces which occur due to acceleration and deceleration – always taking into account the intrinsic weight of the belt and the transported material. They are also used to determine possible curve radii. The company also provides advance feasibility studies.

In addition, the belt position is calculated in advance with the appropriate curve radius for the empty and loaded states. With their slender lines, belt conveyors overcome broken terrain and other obstacles such as rivers, roads, buildings or rail tracks. Horizontal and vertical curves in the routing can also be overlapped.  Depending on the requirement, Beumer offers open troughed belt conveyors for higher throughputs and larger mass flows as well as larger curve radii, and enclosed pipe conveyors for products which need to be protected against the effects of the environment.

At the port of Callao in Peru, Beumer will be installing pipe conveyors with a length of around 3 km to transport copper, lead and zinc concentrates, for completion in 2014.  “Depending on the landscape and environmental conditions, we can install overland conveyors with horizontal curves with lengths of up to 20 km,” explains Oberheuser.Gradients of up to 15o can be achieved depending on the characteristics of the materials to be conveyed. After planning, installation and commissioning, maintenance and service are no more laborious than with a straight conveyor. On average, the annual maintenance costs are only around 2% of the investment sum.

In Canada, Beumer is currently installing a conveyor with a length of 3.48 km for a large mining operation. This will convey up to 6,000 t/h of iron ore. This large-area conveyor system must withstand extreme temperatures of down to -40°C and heavy snowfalls. Beumer has designed all mechanical and structural elements for the extremely low temperatures. For
example, the system is fitted with a feed conveyor and an unloading system with tripper car.

As main contractor, Beumer is equipping a new distribution centre off the shore of Malaysia with 17 trough belt conveyors with a total length of 12 km for a large iron ore exporter. The conveyors will ensure swift transport of iron ore from super-size freighters to the mainland. Beumer will deliver and install the conveyors, put them into operation and take full charge of engineering, all according to a strict timetable.

Codelco has awarded a large scale conveyor system contract for its El Teniente mine expansion to Takraf. The system connects a newly developed orebody to the existing processing facilities. In its final stage it will transport primary crushed copper ore at more than 12,000 t/h.  Running at 6 m/sec, the 2 m wide belt conveyor system will carry the ore over almost 12 km. The three principal conveyors, one 9,000 m long tunnel conveyor and two 1,000 m steep uphill conveyors (15°) feed the existing stockpile and in the future a new stockpile.  The contract also involves the extension of an existing conveyor line. For this it will be necessary to carry out the final tie-in within just a four day shutdown.  Constructability is therefore of fundamental importance to the success of this project and is incorporated in all design aspects.

El Teniente will be able to run the conveyor system initially at lower speeds to suit the lower conveying capacities in the earlier years of production thus saving power and reducing wear. This will further save maintenance costs.  Reduced maintenance combined with its high efficiency and reliability are strong points in favour of the gearless drives.

Even though gearless drives is a well proven technology (mills, hoists etc.) it is relatively new in conveyor design. Takraf, in partnership with ABB, has integrated features within gearless drives which have been standard features for conveyor drive systems for a long time – for example ease of alignment and ease of drive change. The aim has been to reduce the amount of work in the field to an absolute minimum so that a faulty drive can be simply replaced and repaired in the shop.  In order to accomplish this, the motor is mounted on a special base frame.  This also allows the use of standard pulleys – another important feature. The configuration of the direct drive unit can induce very significant forces into the pulleys which have caused considerable problems with pulleys in the past.  With the Takraf design this has been eliminated.

The company says that its “innovative approach has produced a reliable and easy to maintain drive concept combining proven technology with state of the art direct drives.  Particularly the long tunnel conveyor has been designed to minimise its running resistance by ensuring accurate alignment through special conveyor frames and the use of low running resistance rubber compound for the belt.”

The two steep inclined conveyors, which in their final stage will be both equipped with four 2,500 kW drives, presented some challenges particularly regarding the service of the idler rolls along the conveyor run, which is mainly in tunnels. With heavy idler rolls manual handling is not only difficult but carries a high risk of injury for the maintenance personnel. For this reason Takraf has developed a unique system to service these steep conveyors. A special maintenance cart straddling the conveyor has been designed to minimise the tunnel cross section. It is equipped with a small service crane and runs on rails along the entire conveyor length. The crane is fitted with special lifting frames which pick up the rolls and help to place them in position. The maintenance personnel only need to ‘manipulate’ the rolls, the weight is taken by the crane. The cart can carry spare rolls, all required tools and up to four people.  This makes idler roll changes a safe and easy task. Special attention has also been paid to safety with independent and fail-safe braking and clamping systems.

Leach logistics

Heap leach operations continually seek greater capacity, continuous material flow, and reduced downtime. In any application, these challenges are ongoing top initiatives, particularly due to the complexity of stacking plans. Material handling equipment must be highly mobile and extremely flexible. And, for optimum performance, more and more operations are using integrated conveyor systems, which can be custom-engineered for the specific pad design. The speedy payback from the latter is
measured in more tonnes per move, larger leach pad footprints and increased profitability.

“Because every heap leaching operation maintains a specific process with unique characteristics, mines are far more likely to improve efficiency with a customised and comprehensive material handling system,” explains Jarrod Felton, Vice President of Engineering for Superior Industries, a manufacturer of mine-duty conveyors, components, and integrated systems customised for small-to-large heap leach operations; and suitable for valley fill pads, billiard table pads, and advance or retreat stacking.

Felton says that an integrated heap leach system is comprised of a core group of mineduty conveyors, with the customisation of the system being applied with various belt lengths and widths, belt speeds, and load areas; as well as choices in hoppers, mobile tracks, control systems, electrical components, and the total number of jump or grasshopper conveyors.“This strategically selected system of machines and machine attributes ensures smooth material transfer and far greater efficiency over that of older, conventional methods.”

He explains that currently many heap leach mining operations work in a manual radial stacking mode. Operators will move the radial stacker with a loader to a given location, leaving it to stack there while they perform other maintenance duties. Later the operators return to either fill in holes or move the stacker to the next location. “This typically results in sawtooth pile tops, which are not ideal for irrigation,” he says.

Alternatively, automated heap leach conveying systems are programmed to stack per desired lift specifications. The core of such a system could be the mine-duty TeleStacker® conveyor, which is engineered with an internal stinger conveyor that maintains constant motion along a cell, distributing material evenly to achieve a flat top to each heaped pile, while also piling more material per move. “Its longer stinger conveyor, over that of conventional radial telescoping units, allows for greater flexibility in complex valley fill applications,” says Felton. He explains that the conveyor is equipped with the FD Series Axle assembly, a technology that allows a quick transition from radial to linear mode, enabling movement along the leach pad cell centreline. Also, the unit features the patented FB® Undercarriage support system, which is constructed of durable steel and a tubular braced structure that prevents any twisting and shifting. “This level of stability is required for the uneven ground and the constant movement typically seen in the heap leach environment,” he stresses.

As to additional mobility options, Felton says that operations may use radial travel tracks and/or a track-mounted mobile pivot base in conjunction with the telescoping conveyor.  “Radial travel tracks are a cost-effective method to gaining optimum flotation and traction.  When combined with the mobile pivot base, operations can achieve free-ranging onsite and transfer point mobility as well as radial travel capability – all while reducing the need for multiple trucks and loaders,” he says.

The Horizontal Index Conveyor (HIC) can Integrate with the telescoping radial stacker.  The HIC is a fully-skirted unit with a frame that mounts to the stacker.  “For greater heap leach site mobility, the track drive on the unit is designed to move itself and the radial stacker along the cell centreline – and for maximum flexibility, the HIC can be fed at any point along the length of the conveyor,” says Felton.  He adds that when combined with portable jump or grasshopper conveyors, the HIC minimises the frequent removal or adjustments of the jump conveyors along the material transfer line.  “Ultimately, the combined mobility and flexibility of the HIC is key to building larger leach pad footprints,” he says.

Next, Felton explains that a horizontal feed conveyor runs perpendicular to both the HIC and the grasshopper conveyors. “It transfers material from the grasshopper conveyor to the HIC to maintain a consistent, steady material flow,” he says.

Built in standard lengths of 30.5 m (100’) or engineered in custom lengths, multiple grasshopper conveyors comprise a substantial length and are combined consecutively to transfer material to the stacking conveyors.  Felton says that retreat stacking will move in increments of the grasshopper conveyor length by removing one at a time, while advance stacking requires the insertion of a jump conveyor upon moving forward.  For very large systems, there are ‘super’ portable grasshopper
conveyors that range from 65.5-76.2 m (215-250’) in length.

“Operations can also utilise a tugger, which is a self-contained and tracked mobile pivot base, to move grasshopper conveyors into place.  It can also be used as a single point axle on a horizontal feed conveyor,” says Felton.  He also notes that the company’s new Trailblazer® Portable Groundline Conveyor can be used to replace some the grasshopper units. “This gives the system the advantage of fewer transfer points and electrical connections, and lesser move frequency,” he adds.

While a total systems approach to heap leach conveying may seem an unwieldy proposition to some operations, Felton stresses that adaptability is made easier when the systems provider also takes a total approach to the design/build factor. “Today it’s common for manufacturers to sub-contract to others for both large and small components. At Superior, we manufacture all our components and conveyors, and engineer our systems as a whole to ensure such things as smooth material movement at all transfer points as well as the necessary electrical integrity required for the integration of multiple conveyors, for example. Our approach also allows greater control over lead times and delivery,” he says.

From system installation through startup, Felton says that his team provides onsite assembly and training. “This ensures safe operation and allows the crew to experience productivity right from the start.”

Lastly, Felton points to the fact that Superior Industries was founded and built on the premise of making conveyors mobile, and minimizing the need for costly loader, dozer and haul truck use.  “So it is no surprise that we are drawn to the heap leach mining market as it has one of the highest requirements for mobility,” he says.

Thor Global has delivered a ThorLoPro low=profile portable radial telescopic conveyor to a gold heap leaching application in Mexico.  Here, crushed ore is conveyed from two separate crushing plants into a surge pile that feeds multiple transfer conveyors, a bridge conveyor and finally the LPT140x42-1200, 42.7.m by 1,050 mm low profile telescopic stacker.

The company says “the LPT140 fits perfectly into the site’s existing low profile bridge or indexing conveyor via a rotating pivot pin system.  Thor Global designed a custom removable fifth wheel pin to accommodate this unique operations mode anchoring system. The patented low profile design has the added benefit of preventing spillage due to the fact that the feed point height remains constant while the conveyor is being raised and lowered.  Dual radial wheel drives was an essential optional feature for this application in order to overcome the inherent difficulties of operating over several layers of previously stockpiled material.

“Thor Global’s patented push-down axles are instrumental in providing a seamless live operation for this application. This optional feature allows the operator to move the telescopic conveyor multiple times without shutting down any belts in the conveying sequence. As the push-down axles are engaged the radial arms rise off the ground, while remaining in their fully extended radial mode.  The bridge conveyor then pulls the telescopic back into its next position. During this entire transition, material continues running off the belts, non-stop.

Managing the system

Twiflex, part of Altra Industrial Motion, has introduced a new disc brake for mining conveyor applications. The VBS modular brake features large pads and IP65 protection, making it ideal for high speed conveyor drives. The brake also benefits from Twiflex’s ‘Parked Off’ safety feature; the only system of its kind to allow completely safe maintenance and pad removal, the company says.

This new modular disc brake complements the existing range of conveyor brakes. The VBS is a ‘fail safe’, spring applied – hydraulically retracted disc brake calliper which consists of two modules mounted either side of a central mounting plate. Intended for use on high speed drives on downhill conveyors the brake uses large pads (10,283 mm2) for high thermal capacity and is fully sealed against moisture and dirt ingress.

Steve Powell, Product Manager for Twiflex, comments: “The brake is installed between the motor and gearbox to protect the motor against overspeed conditions when there is a mechanical failure in the drive.  The VBS is easy to install and is fully interchangeable with most brakes on the market which makes swap-over extremely quick. The added benefit to the VBS over other brakes on the market is the ‘Parked Off’ feature which makes maintenance work far safer than anything else on the market.

“For many years much has been made of safety features in industrial disc brakes, with manufacturers claiming to provide ‘safety lock out’ during adjustment and pad replacement.  With the exception of the Twiflex ‘Parked Off’ feature, all of these designs use a mechanical lockout system which utilises a nut and centre bolt arrangement. This method relies on the integrity of the nut and bolt to hold the spring force; if this fails then the brake will close, potentially causing extremely serious injury.

“In ‘Parked Off’ the disc spring load and hydraulic pressure in the Twiflex design are zero, meaning the VBS has no stored energy and therefore completely safe for maintenance / pad removal. The position can quickly be achieved in the field with basic tools making the brake 100% safe without reliance on mechanical lock out.  This feature also allows the brake to be installed without the need for hydraulic pressure.”

Powell continues: “We always try to consider the real world problems faced by engineers in the field when designing our latest products. I believe that the ‘Parked Off’ feature represents a real and unique step forward in personnel safety.”

South African conveyor equipment manufacturer Melco, which supplies modular conveyor structures for underground mining, has expanded the reach of its products into more than 75 countries worldwide. Melco Managing Director Gavin Hall: “Melco specialises in the design, manufacture and supply of conveyor idlers, rollers, motorised pulleys and supporting structures.

Melco has been a member of the Rulmeca group of companies since 2006. “Almost all of Rulmeca and Melco’s activity involves the design, manufacture and sale of idlers, rollers and motorised pulleys for bulk materials handling applications,” notes Hall. “As a group, we have chosen to specifically focus on this core business, to ensure that we remain experts and leaders internationally, without being distracted by non-core activities.”

As part of its value-added service and commitment to complete customer satisfaction, Melco Sales and Marketing Director, Craig Warmback points out that the company has established the Melco School of Belt Conveying, which is dedicated to promoting the safe and efficient use of conveyor systems.

Rulmeca reports that Hutchinson Salt Co recently replaced the 20-year old drives on its storage shed feed and take-away conveyors with Rulmeca Motorized Pulleys at the deep salt mine in Hutchinson, Kansas. Reliable plant production was in jeopardy because the original exposed motors, gearboxes, pulleys, and pillow blocks were near the end of useful life. The corrosive effects of handling raw salt with electrical and mechanical components are well known.

Hutchinson Salt decided to replace the exposed drive systems with hermetically-sealed internally-powered drives because they were aware of the Motorized Pulley’s effectiveness in resisting corrosion. Specifications included stainless steel end housings and shafts, special paint, regreasable labyrinth seals, and solid ceramic lagging bonded to the pulley shell.

Based on Rulmeca’s recommendation, Hutchinson Salt changed the drive on the 135 m long storage shed feed conveyor from a single 30 kW head drive to a ‘dual drive’, consisting of a model 400M at 15 kW with a 2 m/s belt speed at each end of the conveyor. This accomplished two things. Firstly it eliminated problematic belt bounce and material spillage at the discharge tripper, as shown in the photo, and secondly it enabled one spare to back up the entire shed handling system because the shed take-away conveyor required a 15 kW drive with a 2 m/s belt speed.

After using the Rulmeca Motorized Pulleys for a couple months, Harold Mayo, Hutchinson Salt Co representative said, “We are perfectly happy with the Rulmeca Motorized Pulleys now. The shed conveyor, as of today, is functioning better than ever. It is as close to perfect as it can possibly be.”

Hutchinson Salt’s experience is typical of producers of corrosive salt, phosphate, potash, and fertiliser who have invested in Rulmeca Motorized Pulleys. For example, Cargill Deicing has had numerous Rulmeca Motorized Pulleys in service at its deep salt mine in Avery Island, Louisiana since 2004, from the small 15 kW model 500 up to the 55 kW model 800, with corrosion resistant paint, regreasable labyrinth seals, and solid ceramic lagging.

Rulmeca is constantly seeking opportunities to solve customer conveyor drive problems, such as corrosion and belt bounce. Another example of a belt bounce problem is at the Buzzi Unicem plant at Pryor, Oklahoma. When the plant replaced a single head drive with a dual (head and tail) drive system on its 167 m long tunnel reclaim system in 2011, they also eliminated more than 1 m of belt bounce and subsequent belt damage during “empty belt start-up” in the conveyor’s concave curve section. In fact, since it provided 360° instead of 180° of belt wrap, the dual drive configuration reduced slack side tension by 1 t and enabled the plant to re-use the trhree-ply belt, in spite of the fact that drive power was increased by 33%.

David Brown showcased the improved CX series of dedicated conveyor drives earlier this year at Coal Prep in April 2013. The company states “the CX series offers a design dedicated to conveying applications without compromise and offers superior performance in comparison with competitor’s standard general purpose gearbox offerings.  The advanced technologies of the CX series provide key product solutions for mining operations, including:

• Up to four times longer bearing life
• Up to 20% greater thermal capacity, without the need for ancillary cooling equipment
• Precision gear tooth profiles reduce noise and maximise power transfer
• Optimised rugged cast iron housing with superior power to weight ratio
• A unique flippable design with modular mounting options.”

Mark Hollingworth, Director – Mining at David Brown said: “We’ve had a great reaction to the CX series from the mining industry and we strongly believe that it represents the most highly optimised solution for conveyor drives on the market today. It has already been proven to be extremely reliable and low in maintenance in very demanding environments and stands to make a significant and positive impact in mining operations anywhere in the world”.

Customers choosing CX series conveyor drives will also benefit from a new three-year extended warranty package ‘3X’. The 3X is available for any gearbox brand and model – even those of competitors repaired by David Brown and provides access to David Brown’s global network of service and repair centres for speedy local service (IM, March 2013, pp72-74). The 3X package also covers new installations of gearboxes designed and manufactured by David Brown.

Gearboxes will be installed, commissioned and maintained at regular intervals by a specialist David Brown service engineer under the warranty, a warranty that includes the option to install CMaS, a remote conditioning monitoring system, which gathers critical information while the gearbox is in operation, warding off the risk of unexpected failure.

Stieber Clutch launched its new RDBK load sharing, high-speed, releasable backstop at this year’s Hannover Messe. This compact product has increased torque capacity compared to conventional designs, which helps avoid the over specification of gearboxes to meet large outside diameter requirements of some backstops. In the event of a blockage, belt jam or overload, the RDBK allows for a controlled release under load and is able to rotate backwards for maintenance and clearing work, unlike many other designs that offer limited reverse rotation after being engaged.

In most large conveying applications, backstops are installed onto the gearbox to prevent the conveyor from rolling backwards in the event of a breakdown. To satisfy customer demands, many backstops now include load sharing/torque limiting and releasable functions which help to reduce downtime once the backstop has been engaged.

However, to cope with the high torque loads their design footprints are often quite large which means oversized standard gearboxes must be specified for them to fit. This can negatively affect the cost and overall efficiency of the gearbox. Traditional backstops can also make repairing the fault extremely awkward.  While they prevent any immediate damage being done by uncontrolled reverse rotation, they also prevent the conveyor from being easily unloaded prior to maintenance. Even designs which allow for controlled release only provide a small amount of reverse rotation.

Built on many decades of experience of manufacturing backstops for demanding conveying applications, Stieber Clutch has developed a new, compact backstop design which allows the correct sizing of gearboxes as well as offering reverse rotational capability with a simple hand-operated hydraulic or mechanical release. The RDBK is a centrifugal lift-off, sprag-type backstop with an internal limiter which is designed for use on the high speed or intermediate shaft of the driving unit in multi-drive systems, such as on large inclined conveyors, where two or more backstops share the reverse load.

With a maximum torque capacity of 170,000 Nm the unique, compact design gives it up to 3.5 times more torque capacity than conventional designs of similar sizes; with up to 15 times more energy dissipation. To make sure that it remains functional after long periods of inaction, the friction linings work in an oil bath, providing a consistent coefficient of friction even after long periods without engagement.

The release function allows the tension of a jammed belt to be released through an internal hydraulic system. The release is performed using a simple hand pump to actuate the internal hydraulic cylinder; progressively releasing the backstop (a mechanical alternative is available).  When the oil pressure is released, the backstop is automatically re-set to the original slipping torque. The operation can be controlled and halted at any time, helping to boost productivity. Where multiple backstops are employed, these can be linked and operated simultaneously from a centralized control location.

Belt strength

Fenner Dunlop Engineered Conveyor Solutions in the UK says it has led the way in the development of fire retardant conveyor belting for underground mine use since back in the 1950s, its PVC impregnated solid woven belt being one of the key factors in mine safety over the last 60 years. Since then significant changes have taken place, both in terms of more stringent safety requirements and a greater demand for heavier duty belts to meet ever increasing production needs.

As Sales Director Jim Jones points out “around the world today we are seeing great pressure on mines for optimum output with minimal downtime but also, at the same time, a much greater emphasis on miners’ safety which we wholeheartedly support. Our principles are based on the premise that an underground conveyor belt should never be the cause of a fire, should be very difficult to ignite and, if the belt is ignited from an external source, should never propagate the fire.”

Following extensive research and development carried out by its in-house team of technical specialists, Fenner Dunlop UK has developed a new heavy duty belt for its solid woven range – Fenner Dunlop Type 18000 (tensile strength 18,000 lb/in or 3,150 N/mm), hitherto a tensile strength that could only be achieved with a steel cord belt.

The development of a solid woven belt to meet this tensile strength was one part of the challenge although the most difficult aspect for the team was to design a belt of this strength which could also meet the required global underground fire safety standards. “We know that the steel cord belts that Fenner Dunlop manufacture at various plants around the world can easily handle the tensile requirements but these are generally not able to pass underground safety standards due to the steel cables used in the carcass” added Jones.

“We are therefore extremely pleased to announce that we have achieved European approval to the underground safety standard – EN14973 Class C1 for both PVC and rubber covered Type 18000 solid woven belt, the most demanding safety standard for underground use. This belt, along with all others in the Fenner Dunlop solid woven belt range, is certified to Class C1 and can therefore be used safely underground, in potentially explosive environments, without the need for secondary fire safety devices on the conveyor.”

To secure this approval, the belt had to pass demanding tests on flammability, gallery propagation and, perhaps most importantly, drum friction. It was the introduction some years ago of the drum friction test (which simulates a stalled belt and continually running drive drum) that has arguably been the major contributor to conveyor belt fire safety underground in recent times.

ASGCO®’s Impact Cradle Beds are (patent pending) designed to provide protection to conveyor belts from impact damage from large rocks, tramp metal, roof bolts or bucket teeth that can put a stop to operations. The modular style impact beds provide impact protection for the conveyor belt, as well as a tool to help control spillage in the conveyor-loading zone.  The Impact Cradle Beds support the conveyor belt across the entire width using ASGCO’s unique semi-U-shaped design that eliminates any unsupported areas between the rollers or bars on traditional impact idlers or traditional impact beds where damage can occur in the idler junction points. The cradle beds consist of a heavy duty frame with removable (slide-in or slide-out) sides and centre sections for ease of installation and maintenance.

• Improved Impact Cradle Beds – no pinch point or idler junction area using 17.5° bars for 35° idler systems; 10° bars for 20° idler systems and 22.5° bars for 45° idler systems
• Absorbs impact – with heavy duty steel designed framework and impact bars that are manufactured with absorbent, 40 durometer rubber that can really take the shock of large material
• Modular designed – cradles can be manufactured in 600 mm, 900 mm, 1,200 mm or 1,500 mm lengths, depending on the size of the material impact area
• Available in either standard duty or mine duty (twice the impact resistance).

The new ConquestXP™ primary crusher belt is backed by the power of Fortress™ Technology, an innovation in rubber
compounding and reinforcement technology.  ConquestXP is built to excel in impact and puncture resistance. Including one ply 330, oneply 440, two-ply 660 and two-ply 880, and available with Goodyear Engineered Products compounds like Defender®, Stacker®, Survivor® and Global X®, this belt is ready for anything you can throw at it, the company says.  ConquestXP conveyor belts are designed to withstand the harshest above-ground belting environments, developed using intense computer modelling and finite element analysis (FEA) software, extreme testing and backed by over 100 years of innovative rubber compounding research. It is designed for primary crushers, secondary crushers, mainlines, pit belts and many other high-abuse applications.

Veyance says “the new dual layer twill fabric gives ConquestXP improved load bearing and impact resistance. [It] has industry leading impact resistance. Loading point impact damage can be a major cause of belt failure. Design engineers used an enhanced dynamic impact tester to simulate loading impact force and its effects on belting.

“The dual layer twill fabric design enables high transverse tear strength. This minimises tears that result from material punctures as well as edge tears from misaligned belts.  “Scrap metal or debris often get ‘hung up’ in the structure of the conveyor, causing equipment damage and slits or cuts in long sections of the belt. Our fabric design helps dislodge and expel foreign objects and contain rips to a small area.”

Germany’s ContiTech Conveyor Belt Group is strengthening its conveyor belts business for industrial applications with the acquisition of Metso’s industrial conveyor belt operations based in Helsinki, Finland. The transaction includes a production plant in Kalkku, Finland, where ContiTech will continue to manufacture conveyor belts for use in the minerals industry. ContiTech also acquires the related sales and service locations in Finland. In total ContiTech will take over approximately 130 Metso employees. Both sides have agreed not to disclose the purchase price. Transfer of the business is scheduled for Q4 2013.

“The acquisition strengthens ContiTech’s industrial business and is the perfect complement to the Conveyor Belt Group’s current range of industrial conveyor belts and special belts. Furthermore, we are also improving our market presence in northern Europe and optimising the structure of our production sites,” says Hans-Jürgen Duensing, Head of the ContiTech Conveyor Belt Group business unit. “Our objective is to continue and further develop activities at the plant in Finland and gain access to new customer groups in the Scandinavian markets.”  In 2010, ContiTech took over business activities involving Flexowell and Pocketlift conveyor belts from Metso and has since then successfully expanded business in this area.

Conveyor Belt Monitoring (CBM) notes that together with condition based maintenance, planned maintenance comprises preventive maintenance, in which the maintenance event is preplanned, and all future maintenance is preprogrammed. Planned maintenance should be established for every item separately according to manufacturer’s recommendation or legislation. The plan can be based on equipment running hours, date based, or distance travelled.  A good example of condition based maintenance in conveyor belts is the amount of damage a belt suffers as the ‘warning sign’ before it is repaired or replaced, but how do we gauge these warning lights if there aren’t enough warning lights? A combination approach to monitoring internal damage and external damage is needed if real savings are wanted.

Interestingly, downtime costs recently surveyed on one particular mine were estimated to be A$130,000 per hour. We all like to save money but we can clearly see that saving downtime can pay monitoring systems back over and over again. Comparing simply outage time inspecting a belt at A$130,000 per hour doesn’t seem sensible; even if it’s only an hour per shutdown, say every two weeks, it adds up to over A$3 million/y in lost revenue.  Installing a low cost solution monitoring system will save a lot of money.

An innovative vision detection system, CBM’s Beltspy, has been designed to inspect conveyor belts for damage that could lead to catastrophic events.  Comprising of a single workstation, located in an office or control room, this system allows the operator to perform an inspection of the conveyor belt covers by visually analysing high resolution images anywhere along the conveyor belt. The system can be configured to inspect either carry or pulley covers, or both.

Beltspy captures the image ‘while the conveyor is in production’ allowing the operator to inspect damage and identify repairs without the need to stop the belt saving valuable dollars without downtime.  The system employs proprietary processing algorithms to automatically detect and flag clips, splices, damaged conveyor belt surfaces and belt edges. The system maintains precise conveyor belt metrics relative to reference location. The locations of all event distances are stored by the system thus providing instant access to event images. Sequential conveyor belt browsing is also available.

Inspecting the internal condition of the conveyor is, for obvious reasons, difficult and basing repairs solely on external diagnosis can be costly as there is no need to replace belt if the internal integrity is intact. Therefore internal condition monitoring is a prime way to save thousands of dollars.

24/7 monitoring of the steel cords is imperative and can provide immediate security against catastrophic damage and limit the amount of spliced repairs needed. Diagnosis of the cords can determine broken cords, cord corrosion and splice anomalies leading to splice failure. One of the worst fears for a site is belting coming apart and slipping down a drift or damaging structure, or worse, human injuries.  The cost of downtime and clean up is devastating to bottom line profits. 24/7 Steel Cord monitoring also offers (DED) Disastrous Event Detection to shut the belt down in the event of any cords broken bringing the integrity of the belt into question. So immediate temporary repairs can be made enabling the belt to perform until the next planned shutdown. Another unique feature to the 24/7 cord scanning system is the ability to auto stop a particular portion of damaged belt to the pre-designated repair station. This saves valuable downtime by not overshooting the repair station and having to cycle the belt again.

Phoenix Conveyor Belt Systems has launched what it describes as “a revolutionary conveyor belt monitoring system, the Phoenoguard PX. It is an all-for-one 24/7 device, which detects any deficiency of a moving conveyor belt – inside (-> steel cords, textiles, splices) and outside (-> rubber covers).  Alarms and recommendations are triggered as per the users requirements.”  Phoenoguard PX automatically detects, in realtime:

• Corroded or broken cables, protruding cables and cable misalignment
• Stuck foreign bodies
• Longitudinal cuts, grooves and slits, holes,punctures, edge damage
• Insufficient belt cleaning, excessive wear, mistracking, belt vibrations
• Deteriorating or opening splices.

At regular intervals, a detailed analysis of the entire or any specific part of the belt is provided.  This notes critical abrasion and wear (thickness profiling), and classifies damages – including a belt life forecast.  The unit is permanently installed and suited
for belt speeds of up to 10 m/s.  It operates contactless and is almost maintenance-free. It is a highly reliable and safe technology, Phoenix reports. “There are no manipulations of the conveyor belt required. The use of Phoenoguard PX increases conveyor safety, extends belt life, and drastically reduces maintenance costs and the number of conveyor shutdowns.

Flexco notes that rollers “tend to be one of the least-considered components of a conveyor system. In part, this is because individually they tend to be less expensive than other components and it is difficult to track their life and performance. But a failed or seized roller is no small matter. It can cause serious problems for an operation, from costly belt damage to extended system downtime –– along with posing serious safety hazards for employees. With conveyors comprising most of the haulage loads in this day and age, having rollers that wear longer and perform better can increase the efficiency of your operation.”

The company recently announced the addition of the CoreTech™ line of rollers to its wide range of products designed to maximise belt conveyor productivity. The next generation of troughing and return rollers is made of lightweight, high strength, corrosion- and abrasion-resistant composite materials.

Designed to overcome common issues with belt conveyor rollers, CoreTech rollers are durable enough to tackle a variety of environments, feature lightweight construction, require less energy, and emit less noise than steel counterparts. The rollers provide the same CEMA (Conveyor Equipment Manufacturers Association) ratings as steel rollers with no loss of functional performance, while providing a longer service life and superior wear when compared to steel.

Not only is the material durable enough to resist abrasion and friction on the surface of the roller, the field-proven seal design offers unmatched corrosion resistance and bearing protection on the inside of the roller. The centrifugal seal also prevents trapped material from damaging the end disk, which can result in premature roller failure.  Despite the heavy-duty construction and solid performance, CoreTech rollers are 40-50% lighter than steel. In most cases, a CoreTech roller requires only one person to lift, carry, and place, requiring less manpower and increasing productivity, while adhering to one-person lifting limits.

With low breakaway mass, the rollers also require less energy or torque to start rotation.  This, plus a low running friction, decreases power consumption and can contribute to lower electric bills.  CoreTech rollers also create far less noise than steel rollers. The notable difference can make an impact on worker safety and save an operation from costly fines associated with noise pollution.

Preventing spillage

Two global innovators in bulk material handling have formed a strategic alliance specifically to design and manufacture state of-the-art conveyor solutions for engineered transfer points. The news comes from Martin Engineering, a world leader in making bulk material handling cleaner, safer and more productive, in partnership with CCC Group, an internationally-recognised general contractor that delivers construction, manufacturing, design and engineering services.

By the terms of the agreement, CCC will design, engineer and install the chutes, with Martin Engineering delivering the transfer point components, including load zone and settling zone. “CCC will take the lead on all projects, with Martin support during system specification, design, installation and commissioning,” explained Martin Engineering USA Managing Director Mark Huhn. “We will be providing components such as impact cradles, engineered chute walls and trackers, as well as skirting and sealing technologies.”

The primary benefit to customers will be a very specific focus on transfer points involving two pioneers in material handling technologies.  “CCC’s focus and engineering expertise in chute design will be complemented by Martin’s experience and innovation in product design and service,” Huhn continued.

An innovative Martin Engineering impact cradle design is protecting conveyor belts and structures from falling material in loading zones, reducing equipment damage and downtime while stabilising the belt line to prevent dust and spillage. The EVO® Combination Cradle features steel-reinforced impact bars and adjustable wing supports to match standard trough angles of 20º, 35º or 45º.  “To minimise drag on drive motors, the cradles can be ordered with centre rollers instead of centre impact bars,” explained Martin Engineering Global Product Manager Chris Schmelzer. “In either style, eccentrics built into the supports also deliver 5o of wear adjustment, so the alignment between wings and idlers can be optimised for effective transfer point sealing.”

Combination cradles are typically installed so the bars or rollers in the centre are slightly below the unloaded belt’s line of travel. This helps the belt absorb impact, but avoids continuous drag and unnecessary wear if the conveyor is running empty.

Constructed on a base of heavy formed channels to deliver long service life even under severe operating conditions, impact bars are secured with two bolts each, facilitating easy service and replacement. Combination Cradles are available to fit belts from 500 to 2,000 mm wide, and may have as few as four impact bars or as many as 16, depending on cradle size and centre roll option.

Two bar constructions are available: both have steel or aluminium reinforcement, with an absorption layer and a sliding layer of UHMW polyethylene, which delivers a 0.5 coefficient of friction. The first option is manufactured with a 50 durometer SBR rubber absorption layer, and has a service temperature range of -29 to 60ºC.  The second option utilises an 83 durometer
urethane absorption layer and has a temperature range of -29 to 70ºC.

Combination Cradles employ Martin Engineering’s Trac-mount™ technology, allowing the units to slide in and out easily for maintenance or replacement. The modular components are light enough to be removed by one person, without using heavy lifting equipment.

There is also the rugged EVO High Speed Impact Cradle, engineered to withstand brutal operating conditions, reducing roller failures and service requirements. One customer estimates that the new cradles paid for themselves in just the first week of service at the company’s copper handling facility, due to the savings in maintenance and downtime.  “Under high-volume conditions, standard OEM impact idlers in the load zone simply can’t withstand heavy loads and lengthy drops, costing downtime for repairs as well as the expense of replacement components,” observed Martin Engineering Service Technician Doug Brown.

“The new cradle design only requires one person to change the rollers when the time comes,” said Brown. “The biggest problem solved is the downtime. In the past, when customers have needed to change rollers or frames, they had to shut down the conveyor for an extended amount of time,” he explained. “Old style frames can be difficult to remove, requiring that maintenance personnel pull the arms down, then jack up the assembly to pull it out.”

“We wanted something that was slide-in / slide-out,” added Schmelzer. “These new cradles were designed using Finite Element Analysis, so we could confirm that they’d be strong enough, without having to overbuild them,” he explained.  “We can make it as strong as it needs to be, without adding excess weight, so workers can remove and replace components without using heavy lifting equipment.”

The innovative load zone design’s elastomer bar suspension system absorbs and distributes the material load being transferred, greatly reducing the stress on the idlers’ rolling components and support structure. One patentpending design innovation is the use of connecting brackets near the top of the idler frame to hold the three rollers together. These special brackets are designed to allow multiple modular cradles to be tied together, so that the idlers throughout the entire load zone work together as a system.

“This cradle is simple to install, and the easy access to the centre roller makes the maintenance a one-person job,” Brown added.  “In addition to greater durability, it’s intentionally designed to facilitate service, making the task of changing rollers safer and easier.”

Richwood recently contributed to the protection of the assets of a gold recovery operation in the western US with its patented Impact Saddle®. The application uses a 2,400mm wide belt, discharging the primary crusher.  Lump size often exceeds 305 mm, and production is regularly at 3,000 to 4,000 t/h. Drop height here exceeds 8 m.

The previous impact idlers that were originally provided with the system were fabricated specifically for this application but had design flaws that prevented the system from being successful. Richwood says its design “addressed the design and operational flaws, then went on to set new serviceability and reliability levels. Once installed, the system improved belt tracking, belt carcass and top cover wear life, reduced spillage (from side travel), improved dust control (from improved belt support and sealing), greatly reduced downtime and service calls, and substantially reduced overall costs.”

Afterwards, Richwood impact and belt support systems were installed at every transfer in the plant.  Richwood further says Impact Saddle “is consistently successful in the field, even in the most severe applications, because it addresses the shortcomings of conventional idlers and impact beds.”

The Impact Saddle is a bolt-in replacement for conventional idlers and is distinguished by a curved surface supporting the whole area of belt contact. Installed in arrays, the Impact Saddle can replace impact beds or cradles of many feet in length.

Manufacturing of custom designed Weba Chute Systems for Assmang’s Khumani iron ore mine optimisation project (KOP) is well underway. Weba has an existing relationship with Khumani having previously installed a number of transfer points at this Northern Cape (South Africa) operation. The current contract includes the design of ten chutes and the manufacturing of a total of four chute systems which were delivered in the second quarter of 2013.

This latest project calls for three designs of completely new chute systems and a fourth design that will cater for the interface of a new transfer point with the existing Weba Chute system. “Careful consideration was given to the design of all four transfer points to ensure a perfect fit. Our team of engineers, who has extensive experience in designing customised chute systems and transfer points, leveraged this knowledge to ensure that the new system maximises productivity,” says Ted Cruickshank, Weba’s Projects Manager.

Cruickshank explains that in order to optimise the circuit, the conveyors needed to be moved around. “This allowed us to use a portion of the existing Weba system already in operation, which not only simplified the installation but also added to the cost savings for the customer. The top section of the existing chute was redesigned to accommodate any possible contamination while the sampler is in motion. In order to ensure that the existing and new chute systems work together seamlessly, the design tolerances had to be perfect.”

Weba Chute carefully considers the direction of flow and the velocity of the calculated volume and type of material in each application, while also taking into account belt width, belt speed, material sizes, shape and throughput. In this instance, three of the incoming belts are 750 mm wide with speeds of 1.93, 1.57 and 1.71 m/s, with a fourth one being 900 mm wide with a speed of 1.71 m/s. The material lump size varies from 8mm to a maximum lump size of 43 mm. The three 750 mm wide incoming belts have a maximum capacity of 500, 600 and 720 t/h onto outgoing belts of 750 mm wide with speeds of 1.57 and 2.12 m/s. The 900 mm wide incoming belt has a maximum capacity of 1,200 t/h onto an outgoing belt 1,050 mm wide with a speed of 2.4 m/s.

“In addition to the four chutes which were designed and manufactured, we also received the contract for the design of five apron feeder discharge chutes and one trifurcated head chute.  The five apron feeder discharge chutes have been specifically designed to minimise

dust, wear and direct belt impact when the ore body discharges from the apron feeder. The system is intended to reduce the speed of the materials being transferred and this will be achieved by utilising proprietary techniques and reverse flow principles,” Cruickshank says.

“These contracts demonstrate Khumani Mine’s faith in both our design capabilities as well as in the Weba Chute System. Controlled material flow speed, due to the ‘supertube’ cascade effect created by the system’s design, results in decreased dust as well as extended life of the belt. Customers benefit from increased uptime and productivity, together with decreased maintenance,” Cruickshank concludes.

Kinder & Co says “any investment made in your conveyor skirting system is a wasted expenditure unless the belt is properly supported at the loading zone points. The simple installation of belt support is too often overlooked as an unnecessary and overcomplicated piece of conveyor hardware.”

The company’s K-Sure Belt Support System simply uses the existing idler frames and load carrying centre roller, low drag and high performance polyethylene slide rails replace the wing rollers. The extra support created eliminates the belt edge sag and therefore helps your skirting system to work as effectively as it should. “The outcome is a fully functioning conveyor, achieving its full product potential, to control any spillage and contain dust leakage.” IM