Conveyors in Mining
There has been a trend toward long conveyor systems with high capacity single flights, reports Ulf Richter of ABB Automation1. “These conveyor systems are an efficient alternative to costly truck fleets. Also with deeper mines, the use of diesel driven trucks becomes more difficult. Another trend is in underground mining, where conveyors are an efficient alternative to drift hoists or dedicated rail systems.
“Selection of the right electrical, instrumentation and automation equipment directly impacts the performance, flexibility of operation, efficiency, reliability and total life cycle cost of the conveyor system. Conveying systems are required to be solid and dependable and use process repeatable technology, to ensure the highest availability, under the most diverse conditions.
“Based upon ABB’s experience, a comprehensive applications portfolio of conveyors solutions has been developed. The application portfolio includes integrated systems for different types and geometric configurations of conveyors in the mining industry.”
The portfolio includes: Drive systems; Conveyor interlocking, automation and optimisation; Material tracking; Instrumentation; Containerised drive and control system; Conveyor scan solutions. He explains that a lot of information is required to create a control system for several successive flights. “The starting sequence, mass flow separations, ascent and descent angles, bulk weights and distribution, changing operating conditions (particularly difficult to define are belt tensions and longitudinal oscillations) as well as emergency and repair modes and other critical factors must be taken into consideration. ABB uses modern simulation techniques combined with the latest drive and motor technology, such as frequency-converter driven AC motors to provide solutions, aiming for minimised wear, energy efficiency and maximised control. In addition to classic motor starting methods such as binary or the new ABB ECOSS electronic resistor starters, there are Variable Speed Drives (VSD) solutions in medium and low voltage designs satisfying a variety of applications including even the largest and longest conveyor systems.”
Variable speed control allows smooth starting, belt load profile optimisation, belt slack and anti-slip controls, all of which can increase reliability and lower operating costs. The choice between geared or gearless conveyor drive systems usually depends on economic life cycle evaluation and site requirements. Richter says “ABB’s high speed solution (geared) significantly reduces the mechanical stress on the complete drive train. The low speed solution would eliminate the need for maintenance intensive gearboxes and makes high drive powers even possible.”
ABB’s Mining Conveyor Control Program (MCCP) provides the conveyor main drives control. A sophisticated control loop is superior to traditional control methods (such as a basic master – follower) in control accuracy and flexibility. It provides adjustable conveyor speed and offers the potential “to tune a soft start profile (e.g. dwell function) and soft operation at the speed set point for optimal conveying with the maximum transport volume.
“In normal operation, the conveyor will operate in an interlocked mode. This ensures that as [it] is started, the single flights in a conveyor system will each start when the conveyor ahead of it has reached a critical target speed. Belt slip detection as well as running at the torque limit have influence to the interlocking of the upstream conveyor. When in interlocked mode, the whole conveyor system is controlled from a central control point.”
VSDs allow operation at any speed. “This means, for example, that the filling level of the conveyed material on the belt can be kept constant and so matched to the upstream volume and process requirements. This can save energy and will increase mechanical life.
“Material tracking, or Mass Flow Monitoring System (MFMS), is essential where material quality and conveyor load tracking is required. It provides input data for stockpile management or optimum conveyor load control.
The MFMS stores the current amount of material on each conveyor segment, including material properties and provides a virtual overview of current load and position of the load on all conveyors.” Its input data are load measurements provided at those places where the first conveyor along a conveying route is loaded. Laser scanners or belt scales can make this measurement.
“Electrical equipment, such as power distribution, drives and switchgear as well as the control system and auxiliary components need to be properly protected from the harsh conditions [of ] mining. Dust, shock and vibration, extreme temperatures and/or high altitudes require a containerised E-house which is fully air conditioned and vibration proof. It is difficult to create a ‘standard’ E-house solution, therefore each situation must be viewed as unique. Design considerations include factors such as the heat losses, size of the room, available space and reduced cooling capability and electrical strength of the air at higher altitudes such as those found in most mines in South America.”
Richter concludes that remote access to conveyor control is essential to reduce maintenance costs, decrease process downtime and provide ‘proactive’ service. “Avoiding unforeseen system failure and shutdown is the focus of ABB’s Conveyor Scan. [It] combines conventional conveyor monitoring practice with asset monitoring to enable failure prediction [and] to reduce overstressing the conveyor by assisting the operator or control system with helpful alarm functions.”
Reinforcing our comments about conveyors replacing trucks, ABB has won a $140 million order from Vale in the Amazon region in north Brazil, for the Carajas Serra Sul S11D project. ABB says “this is the first time a ‘truckless’ solution will be used on a large scale at an iron ore mine. Truckless systems significantly reduce operating costs and produce lower carbon emissions. If the S11D mine were to be operated using trucks, it would need around 100 offhighway trucks and consume 77% more diesel per year.”
The project will use shiftable conveyor belts instead of trucks to transport the iron ore from the mine to the processing plant. “This unprecedented project will use the latest ABB automation technologies to truly create the mine of the future, a benchmark in terms of productivity, safety and sustainability,” said Veli- Matti Reinikkala, head of ABB’s Process Automation division. “The project will allow Vale to increase production by approximately 90 Mt, while substantially reducing emissions and improving operational efficiency and process safety.”
ABB will provide the automation and electrification to transport the ore into the processing plant, and will completely automate all plant processes. The order includes a centralized 800xA control system for processing operations, so that personnel can be located away from the site, for improved safety and continued production. ABB’s solution also enables the automatic recovery and stockpiling of iron ore by controlling and positioning equipment through satellite signal and via GPS, and by using 3D scanning for field screening.
ThyssenKrupp explains that “gear reducers that have traditionally been used to drive conveyors are reaching their physical limits for demanding applications, such as steep angle or high capacity installations. For example, a conveyor system with a total drive power demand of 20,000 kW or more would require at least eight traditional gear reducer drives, each equipped with 2,500 kW motors.
“Gearless drives are an alternative and an attractive solution for conveyors with higher power requirements.” Of simple construction, a gearless drive system has not only higher efficiency, availability, and reliability, but also lower maintenance requirements in comparison to conventional drive solutions.
With such a system, a slow-running synchronous motor is directly connected to the shaft of the drive pulley. Because of the slow motor speed, a gear reducer is not required. The rotor of the synchronous motor is flanged onto the pulley shaft. Gearless drive technology is nothing new to mining, companies have been installing high power gearless drives for hoists, excavators, draglines, pumps and mill applications for many years. While the technology is similar, the requirements differ for conveyor applications. Similar to mills, conveyors require a lot of torque during start-up, especially in uphill applications. Advances in conveyor belt technology are also supporting the capabilities offered by gearless drive systems. Newly developed stronger belts (ST- 10,000) are now available that can withstand the higher stresses resulting from increased drive power requirements. For downhill operation, the drives are able to work in regenerative mode and supply the operation with additional electrical energy.
The overland conveyor for Xstrata Copper’s new Antapaccay mine in Peru was reported in this article last year (October 2011, p60). It has just been delivered, with a Siemens gearless drive system. Once commissioned it will convey up to 5,260 t/h of ore over a distance of some 6.5 km from the mine to the processing plant. The drive system comprises two low-speed synchronous motors – each with a rated power output of 3,800 kW – and the associated cycloconverters, motor cooling system, converter transformers and complete electrical house for the drive station. A closed loop control system improves load sharing between the two motors.
Superior Industries’ TeleStacker® is a new heavy-duty telescoping radial stacking conveyor. Built for high production, the TeleStacker conveyor offers the ability to stockpile 30% more material per move than similar radial stackers, the company claims, and an operating tonnage ranging from 200 to 5,000 t/h. It is available as a specially configured Mine Duty model designed and built for the industry and heap leaching applications in particular.
A key element of the TeleStacker design is the patented FB® undercarriage support system which offers added strength, stability and safety. Inspired by market requests for longer conveyors featuring wider belts and enhanced productivity, Superior strategically engineered the system with enhanced strength and support in critical stress points, “effectively reducing the deflection of the TeleStacker conveyor by 200% as compared to competitive units,” the company reports.
It is up to 35% heavier than most competitive conveyor machines, leading to enhanced stability and durability. Incorporating a wide base and heavy-duty internal conveyor support rollers, the unit offers heightened safety and stability both during operation and travel – even on rough terrain. Each support roller carries evenly distributed weight, reducing overall stress and extending the unit’s life.
The Mine Duty model is equipped with belt widths ranging from 7,315 to 21,946 mm. Additionally, every unit incorporates mine-duty 2.0 pulleys and idlers, manufactured by Superior.
David Brown, a leading global expert in gearing solutions and services, revealed its innovative conveying system, the CX series, at MINExpo 2012 held in Las Vegas in September. There, visitors to the David Brown booth saw firsthand the newly launched customised conveyor drive system which has been designed specifically for mining, where exceptional performance, improved bearing reliability and increased thermal life are primary concerns.
David Brown says its CX series gearboxes “are designed to operate at extremely highdefined levels of torque, speed, power and thermal ratings – exceeding competitor performance and representing a new, unique best-in-class model. The advanced technologies of the CX series provide key product solutions for mining operations, including: Up to four time longer bearing life; Up to 20% greater thermal capacity, reducing the need for ancillary cooling equipment; Precision gear tooth profiles reduce noise and maximise power transfer; Optimised rugged cast housing with superior power to weight ratio; A unique flippable design with modular mounting options.
Ian Chew, Director – Mining at David Brown said he “strongly believes” that the CX series “represents the best optimised capacities for conveying drives on the market today. It has already been proven to be extremely reliable and low in maintenance and stands to make a significant and positive impact in mining operations.”
Customers choosing David Brown’s CX series conveyor drive will also benefit from the company’s new and market leading three-year extended warranty package ‘3X’. This is available for any gearbox brand and model – even those of competitors – and provides access to David Brown’s unrivalled global network of service and repair centres for speedy, local service and efficient upkeep. The 3X also covers new installations, gearboxes designed and manufactured by David Brown.
Gearboxes will be installed, commissioned and maintained at regular intervals, as necessary, by a specialist David Brown service engineer under the warranty which includes the option to install CMaS, a remote conditioning monitoring system to gather critical information while the gearbox is in operation and help ward off unexpected failure.
ThyssenKrupp recently signed new contracts to deliver overland belt conveyors for Xstrata’s Las Bambas and the BHP Escondida expansion project. Las Bambas will use four gearless drives, each rated at 4,400 kW, while Escondida will install a total of five gearless drive systems – each with a total power of 5,000 kW.
Early this year Sweden’s LKAB commissioned Beumer to provide a curved pipe conveyor for the transport of olivine in summer and quartzite in winter, each at 800 t/h. These are used for to produce high-quality iron ore pellets. The system is at the company-owned trans shipment port in Narvik, Norway. It automates the storage of material and the filling of rail cars, which was done manually. These wagons transport the material to the main plants in Kiruna and Malmberget.
The complete system comprises the feeding area with vibrating feeders, the pipe conveyor with a centre distance of 341.2 m, the steel structure and a reversible troughed belt conveyor feeding the customer’s silos. The pipe diameter of the pipe conveyor is 300 mm, and its conveying speed is 3.1 m/s. Beumer said in the statement: “The decisive factor for the contract award to Beumer was an almost identical system that has been operating very successfully at another mining company for more than ten years. This reference, as well as the good work of the project team during the quotation phase, convinced LKAB. The complete system will be supplied, installed and commissioned by Beumer.”
At MINExpo Martin Engineering showcased its new EVO® Heavy Duty product line specifically designed for mine duty applications, both above ground and below. These products were designed with the same modularity, serviceability and ergonomic design as all other EVO products offered by Martin. “Our EVO product line has been expanded for high speed, high impact applications like mining,” said Martin President Scott Hutter. “Our mine duty EVO line rethinks the problems of traditional conveyor design from the ground up and places more emphasis on safety, control of fugitive material and ease of service.” he added.
In an example of more power equating to less consumption, for some months Rulmeca Motorized Pulleys have been under test at the Hunterston deepwater terminal in the west of Scotland. Hunterston bulk terminal is one of the UK’s foremost facilities for coal imports and the operator, Clydeport, moves coal with 27 conveyors at 3,000 t/h. Reliability of 24 hours a day and 365 days a year are an absolute must and under really hard conditions. Outdated equipment and the desire for modern solutions to minimise energy consumption, lower maintenance, and allow the possibility of networking with the SCADA control system called the Motorized Pulleys into action.
After five years of using Motorized Pulleys (75, 90 and 132 kW) Clydeport is absolutely satisfied, says Peter Little, Engineering Manager: “The Motorized Pulleys have more than proven themselves during this period”. Energy consumption has been significantly reduced. One reason is the minimal slippage on start up and efficiencies through the gearbox. In addition, there were no failures or unscheduled maintenance”.
That gave Clydeport confidence in the quality of the Rulmeca product and so the first 1000 HD Motorized Pulley (250 kW) was installed. This was for Clydeport and also for Rulmeca, not an ordinary installation. A good 4.5 t power-pack is hard to move. After nearly a year of using the Rulmeca 1000HD Little is still satisfied: “There are no problems to this day. Also the 250 kW Motorized Pulley is completely reliable. “
In addition to this, the application of this very strong Motorized Pulley has provided made many more improvements. “We were able to increase the throughput even more, the energy consumption has been reduced and except for routine checks no maintenance measures were required”.
Conveyor belts used in mining typically use considerable amounts of energy. Reducing belt weight potentially reduces energy use and CO2 emission. But before deciding to change to a lightweight solution, can you calculate the benefits? Yes, you can. To support you in the decision, Teijin Aramid has introduced the Customer Benefit Model (CBM). Based on eco efficiency analyses CBM automatically calculates the benefits.
In the CBM, alternative products or solutions can be compared. The model is quantitative and covers both financial and environmental aspects. In the case of conveyor belts, Teijin Aramid’s Twaron and Sulfron products can be used to lower belt weight and rolling resistance. The ecological value of the new solutions can be quantified, as well as the monetary savings and payback time. In this way the CBM can support a decision to change to new, lightweight belt solutions.
Twaron is a high strength aramid fibre with tensile properties close to steel, but five times lighter. This means that a Twaron reinforced conveyor belt weighs considerably less than a conventional steel reinforced belt. A lighter belt results in less mass in motion and reduced energy consumption.
For an existing steel-reinforced coal belt in South Africa – the transport distance is 5,280 m – the CBM calculations estimate that if the steel belt is replaced with a Twaron belt, an energy saving of 15% is achieved due to lower belt weight: the belt mass/m reduces from 32 to 19 kg. Adding Teijin Aramid’s newest aramid product Sulfron to the mix, the rolling resistance of the rubber can be reduced even further. The CBM calculated this nearly doubles the energy saving to 26%.
The power savings are accompanied by large CO2 emission savings. The CO2 savings are not only beneficial for the environment, but, due to emission trading schemes, can also have a financial value in an increasing number of countries.
Veyanceâ€™s new ConquestXPTM primary crusher belt is built “to excel in impact and puncture resistance,” the company says. Backed by the power of FortressTM Technology, Veyance says it is “an innovation in rubber compounding and reinforcement technology. ConquestXP includes one-ply 330, one-ply 440, two-ply 660 and twoply 880, and is available with Goodyear Engineered Products compounds like Defender®, Stacker®, Survivor® and Global X®, this belt is ready for anything you can throw at it.”
Phoenix Conveyor Belt Systems is introducing the brand new St 10000 conveyor belt to the market. It says “this belt will even top the world’s present strongest conveyor belt, a Phoenocord St 7800.
Some 40 years ago, the strongest conveyor belt was an St 4000, used in an underground coal mine in Europe (St 4000, the rating as per DIN 22131, stands for a minimum breaking strength of 4,000 N/mm of belt width). A Phoenocord St 5400 was supplied for the German hard coal mining group RAG, 15 years later. Like the St 4000 it was for a incline conveyor, carrying coal from underground straight to the surface. Another 10 years later, St 6300 belts were used on bucketwheel excavators in German brown coal mining. These giants were 3,200 mm wide, with a total belt strength of some 22,000 kN (2,200 t). They are carrying up to 40,000 t/h of material.
In 1999, the world’s strongest conveyor belt was a Phoenocord St 7800, carrying coarse copper ore downhill from a mine at 3,200 m above sea level. The system is about 13 km long and consists of three flights, of which the top two are equipped with the St 7800. The total drop is 1.3 km. The belt carries 11,000 t/h at a speed of 6.8 m/s downhill and hence is not consuming but generating power. The belt feeds the concentrator with more than 100 million kWh/y.
All the above mentioned super conveyor belts are specially protected with the Phoenotec integral active system consisting of special transverse synthetic single cords, which dramatically increases their resistance against impact and rip damage. Now, even the St 7800, with an actual breaking strength of more than 8,600 N/mm, is not the end. Phoenix has made another advance with the Phoenocord St 10000. To help visualise the strength of an St 10000: Seven Airbus A 380 passenger jets could be hung on a 2,000 mm wide St 10000 – and it would not tear, the company says! The advantages of such a belt are even longer conveying distances and a reduction in the number of transfer points. This drastically reduces belt wear of the belt, bringing down capital and maintenance costs, and increasing availability. Longer distances, until now considered only suitable for other means of haulage can now be managed by economic belt conveyor systems.
Loading the belt
David Morgan and Brian Pittenger, Senior Consultants, Jenike & Johanson comment that some of the fundamentals of conveying are adopting more importance as creative conveying solutions are implemented. New, innovative solutions are being developed to transport more materials, faster, along routes and across terrains that would not have been possible not long ago. The higher belt speeds and variability in materials makes it even more important to get the fundamentals correct, like getting the load centered on the belt quickly and efficiently at each loading and transfer point. Not only does this make the conveying easier but it also reduces spillage, belt wear, dusting and material attrition.
“Traditional methods of transferring bulk materials from one belt conveyor to another are to slam the material into a rock box to kill all of its momentum and then let it fall onto the receiving belt. The receiving belt is used to accelerate the material up to the belt speed. This does not work for high belt speeds and high tonnage rates.
“Dropping the material vertically onto a belt requires an ‘acceleration zone’ where large rocks bounce and roll, creating a belt wear problem, air is entrained in the fines to create a dust problem, and the particles exchanging energy can create a material attrition problem as well. These problems are compounded if the receiving belt is inclined.”
Any variability in the material, such as particle size or moisture content, will make the buildup in the rock box change and the flow through it different. If material drops through the rock box off-centre, the receiving belt will be loaded on one side. “This may result in spillage at the loading point, or if the belt is forced to ride up on the idlers eccentrically, spillage along the route. Trying to keep a large, high-speed belt centered with training idlers under these conditions is very difficult and will often result in more belt wear.
“A correctly designed and efficient transfer point will eliminate these problems because the transfer chute handles the load relatively gently in spite of the high speeds and correspondingly high accelerations.By placing the material on the belt centreline at a speed close to the belt speed, the belt can easily convey it efficiently without spillage.
“Instead of killing all the momentum of material entering the chute, momentum can be used to keep the speed of the flowing material close to the belt speed all the way through the chute. Slowing the flowing stream of material down requires that the cross sectional area increase. This is the beginning of a blocked chute. Also, slowing the material down and then accelerating it again so that the cross section changes rapidly, is an ideal way to entrain air and create dust.
“Balancing the friction in the chute that slows the material down with gravity accelerating the material as it drops from the level of the incoming to the level of the receiving belt can be used to keep the speed through the chute more-or-less constant. Keeping the material in contact with the chute surfaces as much as possible reduces the possibility of entraining air. This also reduces points of impact and the wearing away of the chute at those points.
“Placing the material on the receiving belt centreline at a speed close to the belt speed is also the best way to reduce belt wear and dusting at the interface between the material and the belt. If the chute is designed properly there should not be a need for an enclosed ‘acceleration zone’ with a dust extraction port.
“Jenike & Johanson continues a half-century of innovative bulk handling solutions for conveying applications with continued advances to chute designs both in robust designs and innovative modeling to support the latest in creative conveying technology.”
The Trellex ABC 70 is a patented Metso belt scraper known and appreciated for its effectiveness and long life. Metso states that it has now improved it further, by adjusting the design and materials to increase wear life by 25%, improve its stability and performance, and make it even easier to install. The company has also improved its own production process – making the new Trellex ABC 70 more easily available worldwide.
The Trellex ABC 70 is fully compatible with other Trellex Pre-Cleaners such as the ABC 90 and ABC 95, which means that no mechanical alterations are necessary if changing to a different blade type. Belt cleaning is very crucial to effective, secure and profitable conveying. Because of this, Metso developed a new type of belt cleaning called ABC – Absolute Belt Cleaning. The goal has been to design products with high efficiency, long operational life and a minimum of maintenance needs.
The efficiency of the cleaner in fact governs all its other qualities. The parameters which affect efficiency are amongst others, the angle of the scraper blade against the belt, its contact surface against the belt and its pressure against the belt. The ABC 70, 90 and 95 pre-cleaners keep these parameters as close to the ideal as possible throughout the cleaners’ entire operational life. Metso states: “This results in a very high cleaning efficiency from the day the cleaners are mounted until they are worn out. To further increase the efficiency the cleaner is divided into segments which moves separately for the best flexibility towards the belt. Less spillage means less clean-up and wear on the different parts of the conveyor, which means a lot of money will be saved.”
ASGCO’s Razor-Back MDX is a secondary belt cleaner designed for high speed and maximum tonnage mining systems running in the most aggressive underground and surface mining environments. It says “the heavy-duty, replaceable, carbide-tipped blades effectively clean the conveyor belt with our dual action tensioning systems to maintain even pressure across the entire belt surface.”
The aim is to provide complete cleaning with the combination of belt cleaning blades specific for the application (maximum belt speed 6 m/s) and dual tensioning action from the Spring-Shoc or Air-Shoc tensioner along with the impact absorbing rubber tensioning cushions and conveyor mounting system. The Quick- ChangeTM slide-out mounting system allows for simple removal of the cleaning cartridge from either side of the conveyor system, without having to break the plane of the conveyor structure, or having to remove mounting brackets or the main mounting tube.
Compatible and safe – for mechanically or vulcanised spliced conveyor belts and its slideout blade cartridge allows for improved safety by avoiding workers having to crawl into confined chute areas or underneath conveyor structures. Features include: Eliminates material buildup; Resilient blade support absorbs severestshock in toughest application of underground mining; Blades move independently to maintain contact; Durable, 89 mm thick square tubing for extreme environments; Universal mounting for easy installation; Heavy duty Tungsten Carbide or Hd400 blades available; MDX carbide blade system is three times heavier than any other in the industry, AGSCO reports; Tension by air for consistent control of carryback removal.
Belt and product monitoring
Becker Mining Systems has launched its latest belt rip detection system, the BRS 2. Its aim is to detect belt rips as quickly and reliably as possible. To monitor steel cable and fibre belts, inductive loops need to be embedded in the belt. Once installed the BRS 2 will detect the loops on the conveyor, define and number the loops and create its own image of the belt and its loops in real time. The BRS 2, using its realtime loop diagnostics, continuously monitors the belt’s health and in the event of a rip, stops the belt and reduces any further damage and downtime. Access and the monitoring of the system is simple, either locally with its 12in TFT screen, five shortcut buttons, mouse pad and virtual keypad or remotely via TCP/IP or Modbus. An IS version of the BRS is also available.
Scantech analysers, which can be used to monitor product on belts, allow operators to better use their available resources, meaning that mines can produce more consistent product, which increases efficiency in all downstream industries. Operating costs are thereby reduced along with associated environmental benefits of increasing mine life, reducing waste product, minimising the water used in washing processes and decreasing atmospheric emissions.
The company reported record earnings for the year ended June 30 and a strong forward order book in the opening months of the new financial year. Scantech’s Managing Director, David Lindeberg, said the company has been able to record excellent sales, margins and profits in 2012 “as it continues to improve efficiencies and to supply discerning customers with our quality products. We have many loyal customers and this year, in particular, has benefitted by repeat orders to existing customers that seek efficiencies in their operations in Australia and overseas.
“The company had made a most encouraging start to the new financial year with forward orders for equipment totalling A$7.7 million and the services division – which offers design, installation and radiation services to existing and new Scantech customers – also holding orders in excess of $1 million.”
Spillage and dust
Flexco recently released two new products to improve performance in belt conveyor load zones. It says “EZ Impact Beds provide simple and effective protection in the load zone, while Flexco EZ Slider Beds provide containment to reduce spillage.”
With the same durability found in Flexco’s heavy-duty DRXTM Impact Beds, EZ Impact Beds are available in light- and medium-duty options. Much like the DRX units, these beds feature impact bars for absorbing material impact, while the additional long-wearing UHMW slider bar seals the load zone. Specification and installation of the bed is made easier with adjustable trough angles and universal components. “Maintenance crews can simply lower the troughing angles to provide easy access to the bars and bolts for quick and safe maintenance,” said Ryan Grevenstuk, product manager for Flexco.
EZ Slider Beds are engineered to provide containment around the load zones. They also feature UHMW slider bars to effectively seal the load and provide longer wear life. They are available with optional CoreTechTM impact rollers for superior containment in light impact areas.
Martin Engineering recommends the use of insertable air cleaners on conveyor transfer points to overcome the maintenance problems and operating costs of centralised dust control systems. It recently introduced an updated version of its insertable air cleaner and says “the Martin® Air Cleaner is very effective in applications which create significant dust.”
Rather than carry dust-laden air to a central collector, insertable systems filter the air inside the transfer point where they can easily return material to the conveying system.
It is important to remember that a dust collector does not collect airborne dust; rather it solves the problem of airborne dust by keeping fine particles in the load, by returning them to the main material body, essentially cleaning the air of dust. An integral fan pulls dust-laden air through the filter elements. The air passes through the filter, leaving the particles on the filter element. Each filter element is then regularly cleaned by a ‘reverse jet’ of compressed air, which is injected into the filter element. This causes a momentary reversal of the air flow dislodging the dust cake back into the main material body.
“The Martin Air Cleaner is the next generation of the insertable air cleaners. It features a side access door, making units easier to service and more readily available for regular maintenance. Its rectangular design allows for more flexibility for expansion and it is available in four different configurations to control airborne dust at belt conveyor loading points and other bulk material handling operations.” It features mesh-like material in its filters “which cleans better while consuming less energy than conventional filter bags. The filters allow a reduction of the size of the fans used to move air through the filter elements and therefore reduce the power consumption of the collection system.
The Martin Air Cleaner feature a pulse cleaning system where a short pulse of air is sent back through the filter to dislodge accumulated material. Changing the filter is now a one-hand, no-tool procedure utilising the side access door of the air cleaner.” Insertable air cleaners could eliminate many of the problems seen with central baghouse collection systems, including long runs of ducting, large enclosures, maintenance difficulties and high power consumption. There is no large fan, no ductwork and no central bag house. Insertable filters are integrated into the transfer point enclosure, where they can easily return material to the conveying system.
Rather than carry dust-laden air to a central dust collector, the Martin Air Cleaner filters the air inside the transfer point and can effectively handle the heavy concentration of dust and high volumes of air arising at belt conveyor transfer points. The new line of insertable air cleaners was developed to handle heavy dust concentrations and air volumes at material transfer points. They are designed to remove 99.9% by weight of all dry particulates 0.5 µm and larger (based on a time-weighted average of a properly-installed, operated and maintained unit.) IM
1. Richter U, ABB’s belt conveyor systems portfolio, SME Annual Meeting, February 2012, Seattle, WA