Stockyard systems

ThyssenKrupp’s material handling equipment for Liberian port and mine

In Liberia, iron ore was already being produced before the Liberian civil war. Today,ArcelorMittal is again engaged in the production of iron ore and the product is being shipped as a raw material. In future, iron ore will be excavated from the Yekepa Mine, where it will be upgraded to a high-value concentrate product. It will then be moved by train to the port of Buchanan, whence it will be transported to further processing steel mills.

THE MATERIALS HANDLING EQUIPMENT SUPPLIED BY THYSSENKRUPP COMPRISE:

Mine site

• ROM iron ore blending yard stacker and bride type bucketwheel reclaimer; and
• product (iron ore concentrate) stockyard stacker and bucketwheel reclaimer.

Port site

• high capacity railcar dumper;
• product (iron ore concentrate) stockyard stacker and bucket wheel reclaimer; and v high capacity shiploader.

The mechanical, hydraulic and electrical equipment is engineered and manufactured in Germany and Western Europe, while the entire steel structures of the machines are fabricated in China. The steel structure and mechanical parts will be manufactured there under the permanent quality assurance/quality control of ThyssenKrupp and then assembled with all mechanical, hydraulic and electrical parts delivered from abroad. The iron ore concentrate plant at the Yekepa Mine is equipped with a blending yard and product stockyard. ThyssenKrupp will design and supply the blending equipment as well as the stockyard machines as follows.

The blending yard stacker is designed for stockpiling ROM (run of mine) iron ore in layers with a capacity of 8,300tph (tonnes per hour), while the bridge type bucketwheel reclaimer, with a design capacity of 5,600tph, will feed the concentrate process plant continuously for controlled mixtures of raw materials.

After the process plant, a stockyard is arranged with a stacker and a bucketwheel reclaimer for buffer storage of iron ore concentrates. The stacker receives the materials from the plant and stockpiles them at a rate of 2,500tph.

For the shipment of the product, a bucketwheel reclaimer takes the stockpiled material back to the conveyor system and further to the railway train loading station. To match the train loading operation, the reclaimer will feed the conveyor line at a design rate of 6,000tph.

The end product of iron ore concentrate will be transported to the port via railway for export. At the port, three key components from ThyssenKrupp will be constructed for operation: v one high-capacity railway car dumper;

• stockyard equipment consisting of one stacker and one bucketwheel reclaimer; and
• one high-capacity shiploader

VibraFLOOR was selected to provide the technology to reclaim pelletized biomass from the concrete dome buffer storage vessels currently under construction at Drax Power Station, located near Selby in North Yorkshire, UK.

The project to convert three of the power station’s generating units to run on sustainable biomass in place of coal includes the construction of a biomass fuel unloading, handling and storage facility.

The VibraFLOOR system was chosen by both the client and Shepherd Construction Ltd as the preferred bulk reclaiming option following extensive due diligence, because of the significant advantages over other existing reclaiming technologies.

The advantages included the ability of the system to achieve 100% clearance of stored product without generating dust or degrading the pellets. The capability of removing dust residue safeguards against the risk of self ignition of dust in a storage vessel.

Another decisive advantage is the ability of VibraFLOOR to remove product at very high rates, up to 4,600m3/h.

VibraFLOOR works by creating a wave in the flexible surface plate of each module, instigated by a low power centrifugal vibrating motor, which undermines and collapses the leading edge of cohesive and free flowing material through a low pressure zone, creating a progressive avalanche of the stored material. The collapsed material is gently swept away by the wave action (much as the effects of erosion on coastal cliffs), without causing any product degradation or dust generation, constantly undermining any obstruction or bridged material held in the store.

This flagship project is the first of a number of major developments for utility and port facility companies that VibraFLOOR are involved with, demonstrating the confidence amongst major operators within the UK, Europe and the US in VibraFLOOR’s capability to reclaim pelletized biomass safely and efficiently.

OTHER ACTIVITIES

The marine sector is another field of intensive activities, with six ships on order ranging between 2,000t and 5,000t, all to be delivered in 2014. A woodchips barge is under commissioning in Chile, with a 2,000m3 unloading capability, and a second barge is under construction in Valdivia harbour.

Amongst new developments, self-unloading woodchips trucks are been equipped in Brazil, and self-cleaning flour containers with a single side opening are being fitted with VibraFLOOR in Indonesia.

Conductix-Wampfler is part of the Delachaux Group, which was founded in 1902. The company specializes in the design and production of power, data and media transfer systems for mobile applications. Active on every

continent, the company has Centres of Excellence, responsible for production, R&D, engineering and central support functions located in Germany, France, USA and Italy, with dedicated production centres in Ireland, India, UK, China,Australia and Brazil.

Conductix-Wampfler’s activities are market driven, with emphasis on five focus markets: mining & bulk material handling; ports & container handling; automotive industries; intralogistics; and overhead cranes. The company also works in other markets, such as theatre and stage, people carriers/transit, offshore and construction.

STOCKYARD APPLICATIONS

COMMODITIES HANDLED

Conductix-Wampfler’s solutions are used on a wide variety of mobile/moving equipment, handling the full range of dry bulk materials, from coal and iron ore, to sulphur, pelletized fertilizers, wood chips and grain, plus any other material which requires bulk handling equipment that traverses, slews or rotates during operation. 

SOLUTIONS

With the benefit of a wide range of potential solutions, Conductix-Wampfler’s choice for each application can be made dispassionately, being wholly dependent on the operational and engineering requirement of the application and/or customer preference. The company’s portfolio of products includes:

Motor & spring-driven reels and reeling cables & hoses

For long travel of customers’ equipment, Conductix-Wampfler’s range of cable reels is capable of accommodating reeling lengths of 2,000m or more. There is a range of power and control options, from variable-frequency drive, torque motor and hydraulic drive to the company’s patented MAG drive magnetic coupler. The company was the first to patent this technology in 1974 and its designs include monospiral, level wind, 323 and random or semi-wide spools.

Festoon systems and cables/hoses

Conductix-Wampfler’s festoon systems are used extensively in the stockyard environment. Large I-beam festoons feature on such applications as car dumpers, stacker/reclaimers and trippers, providing multi-cable solutions in

the harshest environments. Conductix-Wampfler’s festoons are hot dip galvanized and have the additional benefit of stainless steel fasteners as standard. Available with a range of roller diameters and configurations, they can be set up to accommodate a wide range of I-beams, with either parallel or tapered flanges, as specified either by the customer, as suggested by Conductix-Wampfler or to fit an existing installation.

Energy guiding chains and cables/hoses

For short travel distances or on applications that require a slewing capability, Conductix-Wampfler can offer a range of steel cable chains, complete with cables designed specifically for this challenging application. Available in hot dip galvanized or stainless steel, the range also includes chains with ATEX certification. For slewing applications, the company has supplied many circular chains on stockyard machines.

Slip ring assemblies

Where applications require infinite rotation of assemblies, for example circular stacker/reclaimers, Conductix-Wampfler can offer a range of solutions engineered in line with operational requirements. Site environmental conditions can be accommodated with a range of Ingress Protection (IP) ratings up to IP67 and with ATEX 21 and 22 certification.

Conductor rails

Conductix-Wampfler also produces a wide range of conductor bars in a variety of materials, specifically designed to accommodate the power requirements and difficult environmental conditions associated with this field

MAJOR CLIENTS

Conductix-Wampfler’s major clients are spread throughout the globe, from major mining houses such as BHP Billiton,Vale, Rio Tinto etc, through ports operators such as ABP, Kinder Morgan etc, to mineral end users such as Tata Steel and numerous power generators.

RECENT CONTRACT AWARDS

Conductix-Wampfler has recently been awarded a contract to supply five motor cable reels for FAM Förderanlagen, Magdeburg, Germany. The reels, which are in two different designs — three with level wind and two with monospiral spools, are to be installed on stacker/reclaimers at Minera Escondida, Chile. The stacker/reclaimers demand a 3.6kV supply, with a run length of up to 891m. The cables are HV (3 phase +PE) core cross section up to 240mm2, with integrated single control core and 24 single mode fibre optic cores for data transfer. Due for delivery in March and April 2013, the reels will be produced in the Centre

of Excellence for cable reels in Belley, France.

CONTINUOUS IMPROVEMENT

Conductix-Wampfler is continuously improving its products. Its patented magnetic clutch system has undergone numerous changes since its initial design and the CN version is the latest incarnation. This is now available as standard on many of its reels. Conductix-Wampfler’s fibre optic rotary joint, the TFO, is wholly designed and manufactured by Conductix- Wampfler and has been specifically designed for use on reeling drums. The company’s competitors do not have such a unit and need to rely on technology which is ‘borrowed’ from other applications. The TFO provides high integrity transfer of fibre optically transferred data between the rotating spool and the static part of the reel. The TFO has also recently undergone a makeover, with a re-engineering exercise which has resulted in a smaller, more easily installed unit.

FOCUS MARKETS

As mentioned above, Conductix-Wampfler has recently undergone a major internal reorganization, implementing a focus market organization, which is designed to enable closer customer focus across the globe. The appointment of a global market manager and global application specialist dedicated to each of the focus markets will ensure, along with the nominated local market managers in each of the specific focus regions, that the company provides the service that its customers expect.

Now, wheel loaders carry the coal to the Telestack tracked mobile hopper feeder which then feeds onto a radial telescopic stacker which stockpiles the coal at speeds of up to 500tph (tonnes per hour) at 1.0t/m3.

With the new Telestack conveyor technology now in place, the wheel loader use is limited. Therefore, there are no wheel loaders driving over the product which means there is no degradation or compaction of the coal, leaving a higher-quality product to fuel the power station. End product quality is further improved by the steeper angle of storage and consequent improved water drainage.

The tracked mobile hopper feeder has a hopper capacity of 18m3 and 21m incline conveyor. The hopper feeder is very versatile and, with the luffing (up/down) facility, it allows the operator to use the unit as a link in the feed system to the TS542 telescopic conveyor to gain distance. It also allows AES to use it as an independent stacker on its own, with a maximum stockpile height of 9m.

The radial telescopic stacker allows AES to stockpile to a maximum height of 12.3m, which enables it to differentiate between the different types of coal better. Also, as coal from different countries, vary in quality and BTU levels; it is important that the stockpiles are segregated to improve the efficiency of the power station. The Telestack system also allows the power station to blend various grades of coal if it desires.

The radial telescopic stacker has an onboard generator (fully sound-proofed), which leaves it totally self powered. It has crawler tracks for easy manoeuvrability around the site. Also, the automatic stockpiling system reduces the labour required to operate the equipment.

RECLAIMING

Before the Telestack system, wheel loaders had to carry the material to the fixed conveyor system. Now,the wheel loaders carry the material over a much shorter carry distance as the new Telestack system makes up a length of 66 metres. This has increased productivity and reduced the downtime necessary to manoeuvre into position.

With fewer loader movements in the stockyard, the site becomes a safer site to work on with less noise. With the new Telestack stockyard system, it also leaves the site more environmentally friendly as it reduces the carbon footprint.

In addition, with the fully mobile Telestack system, AES is able quickly and easily to relocate the equipment around the site.

Telestack offers a range of mobile bulk material handling solutions which are in operation across the globe handling materials such as coal, iron ore, aggregates, fertilizer, grain etc in mines, ports, quarries, power plants, steel mills and cement kilns.

Bedeschi in Indonesia

GRESIK, INDONESIA

In July 2012, Petrokimia commissioned Bedeschi to upgrade an existing fertilizer handling plant. The stockpile will have a length of 200m, width of 50m and storage capacity of 50,000 tonnes.

The design phase of the two independent booms and all the other parts is currently in process and the plant will be supplied by the end of summer 2013.

BEDESCHI IN KRAKATAU INDONESIA

Dong Yang has commissioned Bedeschi to supply four semi-portal lateral scraper reclaimers at a new plant for Posco Steel Company located in Krakatau.

These new machines are equipped with double receiving hoppers with tilting plates. The machines are very particular, because they can unload all material in two different parallel receiving belt conveyors through the double hopper and double lifting impact tables.

This installation required particular effort from Bedeschi’s designer staff in studying the solution that could offer the best performance.

Currently Bedeschi’s technicians are in Krakatau busy supervising and mounting all the parts; the company has therefore fulfilled its required obligations, much to the satisfaction of the client.

CITEUREUP, INDONESIA

In February 2012, Bedeschi signed a contract with Indocement (Heidelberg Group) for the supply of a cement additives crushing storage stacking/reclaiming and transport system.

The system will improve a capacity expansion of the existing plant located in Citeureup Indonesia. Under the collaboration between Bedeschi and its subsidiary, CTP Team has supplied all the filters for the equipment detailed below:

The project will consist of the following:

The crushing group is particularly noteworthy, as the primary roller size has been installed above the secondary one, together with an apron feeder and the circular limestone storage facility that will replace an existing one supplied by a competitor.

Loibl ASH, based in Straubing, Bavarian city of Germany, manufactures a wide range of equipment, largely focused on mechanical bulk solids handling. Its equipment includes a variety of stockyard equipment.

The company, formerly known as Anlagenbau und Fördertechnik Arthur Loibl GmbH (Loibl) prior to its November 2011 acquisition by Diamond Power International, Inc (DPII), offers equipment and systems including:

Loibl ASH’s stockyard equipment is used to handle a wide variety of products, including alternative fuels like RDFs, waste wood and bulky waste. The company’s products include systems for silo and storage technology, processing plants with grain size fractioning, FE and NF discharge or separation, as well as the required crushing technologies and their handling systems.

CONVEYORS

Loibl ASH manufactures conveyors for: power plants; biomass and waste-fired plants (WtE); salt mines; the sugar industry; general industry (e.g. steel); and dry mortar plants. Conveyor systems used in bulk handling stockyards represent a major part of the company’s portfolio. Loibl knows that conveyor belts are extremely important, as a joining element between material handling processes. At the same time, high equipment availability is vital. Loibl makes plants of all types for the industry, including troughed belt conveyors and flat belt conveyors. Belt widths vary from 0.2m to 2.8m+, as well as centre distances of up to several thousand metres. Conveying capacities are up to 10,000tph (tonnes per hour), showing the huge possibilities of Loibl’s conveyor belts. Depending on requirements, the company can deliver stationary, reversible, mobile, swivelling and telescopic systems.

Loibl knows that it is essential to have accurate overall planning and appropriate detail engineering for trouble-free conveyor operations. Its conveyor systems are used in all industrial branches to handle materials such as slag, gypsum, recycling materials, aluminium, sugar or beets, sewage sludge, foundry sand, scrap, alloying aggregates, soot and much more.

Loibl’s expertise has been combined with that of the ContiTech Group to develop the Sicon® system. This innovative system ensures dust-tight and protected material conveying from feeding to discharging without transfer points and environmentally harmful pollution.

Troughed chain conveyors represent an economical solution for many jobs in the bulk handling process. They are ideal, for example, for dust-free conveying, distributing, feeding and cooling of bulk materials. For all fields of application, Loibl’s troughed chain conveyors are made as single- or multi-strand conveyors with centre distances of up to 250m. Depending on the requirements or the conveying capacity, Loibl delivers trough widths of up to 3m. In their construction, St 37 (steel), wear- retardant, anti-corrosive and heat-resistant materials are used, as well as forged fork-type plate bush conveyors or round link chains. Additionally, feldspathic ware, or cast basalt linings are used, depending on the respective application and material.

Other conveying systems offered by the company include worm conveyors, screw conveyor systems, bucket conveyors, vertical life conveyors and sidewall belt conveyors.

SILOS AND HOPPERS

Loibl supplies round and rectangular silos, as well as feeding hoppers of all sizes and with a capacity of up to 10,000m3, with diameters of up to 6m. It also offers individual accessories, such as filling and emptying systems, level sensors, discharge aids, heated or cooled versions and supporting structures of sectional steel, insulation and special linings.

ELEVATORS

Loibl manufactures vertical bucket elevators for the widest fields of application, either for bulk material or, in special cases, for unitized materials. Solutions are always tailored to customer request and specification.

BUCKET ELEVATORS

Loibl produces chain and belt bucket elevators up to a bucket width of 1.25m and a centre distance of up to 80. Fields of application include: processing plants for foundry sand; concrete works; drying plants for sewage sludge; coaling plants; the sugar industry; steelworks and the metallurgical industry.

RECENT ORDER FOR HOPPER CARS

In recent years, Loibl was awarded an order by an internationally operating German crane manufacturer to supply two laterally displaceable hopper cars including discharge conveyor and transfer chute with garland stations towards the following quayside conveyor for a Danish coal-fired power plant in Skodstrup.

Via coupling rods, the hopper cars are connected with a customer-supplied double jib level luffing crane.

Scandinavia, the UK and Poland are strongly growing markets, setting high standards especially for environmental protection and is very conscious of dust and noise emissions as well as of the energy balance.

In order to reduce possible dust emissions, the feeding onto the conveyor belt for the transfer to the longitudinal quayside conveyor has also been equipped with a fogging system.

Special single-component nozzles spray water with a droplet size distribution of 100–500μm.

The booster stations required for the fogging system, valves, valve unit with solenoid valve for atomizing start and stop as well as diaphragm valves for pressure setting are located in heated pump containers.

The hot-dip galvanized piping to the nozzles is protected against damage due to freezing by means of an insulation and heating.

The fourth water-side front wall of the hopper is designed as spillage flap and can be opened and closed via hydraulic cylinder.

The necessary hydraulic units are installed at the respective hopper car. A cover grid with a mesh size of 200 x 200mm retains larger grain sizes.

For noise emission reduction <94dB(A) the hoppers are lined with wear-resistant and sound-absorbing rubber-steel sheet elements and the hopper corners with polyurethane-steel sheet elements to minimize the product deposits.

Additionally, two pendulum-type vibrators on the two lateral faces of the hopper are used to remove the possible coal residues. If necessary, these can be operated alternately and temporarily.

The hopper is monitored with a weighing system including evaluation unit and, if there is the danger that the material will pile up, the crane discharge is stopped.

Weighing electronics are integrated into the control system via Profibus.

For winter operations, the hopper walls and the water atomizing system are provided with an insulation and are heated with a flexible resistance heating cable.

Furthermore the hoppers are equipped with the required stair accesses and maintenance platforms each.

Hopper discharge is made with a sturdy discharge conveyor, which is suitable for use in winter, of 1,600mm belt width and a centre distance of 12,000mm with upstream needle weir. The discharge conveyor is designed with rubberized pulleys, thick- layered rubber belt, inner and outer belt cleaners, closed bottom, corrugated steel sheet cover and all necessary monitoring and safety equipment, as well as a discharging chute with buffer idler garlands and chute walls with wear-resistant and sound-absorbing rubber-steel sheet elements for sound emission reduction <94dB(A).

The overall system is designed to be operated at ambient temperatures from –25°C to +40°C, with a possible air humidity being up to 100% due to direct vicinity of the water.

Power supply to the hopper cars is supplied through the cranes and the speeds of the discharge conveyors are controlled by frequency converter included in the scope of delivery.

The electrical switching and control system to operate the hopper cars, as well as the fogging system, hydraulic system, heating system and lighting system were included in the scope of delivery.

For handling of other bulk material, such as wood pellets, the described version of the hopper cars can alternatively be equipped with an additional dedusting system. In this case, the cover grids of the hopper opening would be replaced by a Flex-Flap System and to reduce emissions a dedusting system with integrated filters be used.

Initial start-up of the sturdy hopper cars combined with the harbour cranes took place in March 2010 and proved their suitability for use in harbours.

CUSTOMER SERVICE

Loibl’s customer support does not end after completion and delivery of the plant. It is at that point that a service begins which Loibl considers especially important — after-sales service. It offers maintenance and service of equipment that it has delivered, as well as for systems from other suppliers. Decades of experience are essential for satisfied customers placing orders with Loibl on the basis of fixed cost or cost-plus-work accounting.

The diversity of stockpile installations poses many challenges for the bulk materials handling industry. Stockpiles are used in many different areas, such as power stations, refineries and manufacturing facilities and for many different types of material. These challenges are well known to Cleveland Cascades Limited, the Teesside (UK)-based manufacturer of bulk materials loading chutes.

“The original Cleveland Cascades chutes were designed for shiploading applications” says Commercial Manager, Chris Wise. “Our customers required a safe and controlled loading of problematic bulk materials, but with the added timescales demanded by port logistics. With stockpile loading, there may not be the exact time- bound demands of ship loading and demurrage charges; however, the requirement for efficient bulk materials loading is still the same, as it is for all our applications”.

Materials that are stockpiled outside, for example coal and coke, tend to be of larger particle size, and maintaining this large particle size during loading and stocking is of high importance to operators, such as steelworks and power stations. The Cleveland Cascades Cascade System allows a controlled yet efficient transfer of material from conveyor to stockpile. The material is supported the full length of the chute by means of an arrangement of oppositely inclined cones. The material is loaded at a low velocity, yet high volume and this means products can be transferred with minimized generation of dust emissions and also minimized degradation and segregation of product. “Since we designed and manufactured the first Cascade shiploaders in 1992, we have seen continued growth from all bulk handling applications, especially stockpile loading chutes. The year 2012 was another record for the business, not just with our Cascade chutes, but also our range of Freefall loading chutes.”

Cleveland Cascades Freefall loading chutes are ideal for robust materials such as iron ore and limestone, or for materials with relatively high moisture content. Recent Freefall installations include limestone loading in the Middle East, iron ore in Russia and metal concentrates in Canada. Freefall systems can be designed to a ‘C’ (cone) specification or ‘T’ (tubular) specification, depending on the installation type, loading rate and material handled. Material distribution is further optimized with the addition of trimmer spouts and skirted outlets at the base of the chutes.

“We offer the customer the widest choice of stockpile loading chutes, from Cascade Systems to Freefall Systems, which can accommodate materials loading at rates from 50 to 6,000 cubic meters per hour. Our approach is for our commercial, design and engineering teams to work closely together, and with their customer counterparts, from project inception right through to project commissioning. What we believe sets us apart from our much larger competitors is that we are able to draw on our previous experience but we are constantly bringing in new ideas and incorporating those of our customers.” 

Conveyors remain the most effective method of on-site cargo transportation, but their reliability can be critical factors in both productivity and cost management. The conveyor belts themselves are often the most vulnerable component because they have to cope with materials that can be very abrasive and, very commonly in cargo transshipment, products that can seriously damage the belt because they contain oil.

During recent years, the technology used to manufacture conveyor belts has advanced enormously and today’s users of belts should rightfully expect a much higher level of performance and longer operational life. Apart from catastrophic accidental damage, conveyors used to transport coal, for example, should be able to run for many years before needing to be replaced. Sadly, this is often not the case. Getting the best advice and guidance is not always easy because for many suppliers and service companies, conveyor belts that last longer and require less maintenance are not good for business. All too often, their philosophy seems to be ‘sell cheap and replace frequently’.

As if to confuse us even further, conveyor belt suppliers (and the companies that fit and maintain them) also seem to have developed a language all of their own. So, for the benefit of our readers who may not necessarily be conveyor belt experts, we asked for help from Netherlands-based Dunlop Conveyor Belting, one of the world’s major conveyor belt manufacturers.

Below, Les Williams from Dunlop explains conveyor belt construction and gives some valuable guidance on how to select belts that will provide the maximum operational life and significantly reduce the amount of money that your company spends each year on conveyor belts.

CONVEYOR BELTS — THE BASIC STRUCTURE

wear caused by abrasion (the most commonly used type), tearing and cutting, heat, fire and oil penetration. These different covers are generally referred to as ‘cover grade qualities’.

MAKING THE RIGHT CHOICE

Selecting the best type of outer cover will largely determine the operational lifetime and ultimately provide the truest test of its value for money. The wear resistance quality of a conveyor belt is usually the single most important factor that will determine its life expectancy. As a general rule, 80% of conveyor belt surface wear occurs on the top cover of the belt with approximately 20% of wear on the bottom cover.

Wear on the top cover is primarily caused by the abrasive action of the materials being carried, especially at the loading point or ‘station’ where the belt is exposed to impact by the bulk material and at the discharge point where the material is effectively ‘accelerated’ by the belt surface. Contrary to popular belief, short belts (less than 50 metres) usually wear more rapidly compared with longer belts because they pass the loading and discharge points more frequently. For this reason, the selection of a belt that has the highest possible resistance to abrasion is even more essential than usual.

Wear on the bottom cover of the belt is mainly caused by friction contact with the drum surface and idlers. The rate and uniformity of this type of wear can be adversely affected by many other factors such as misaligned or worn drums and idlers set at incorrect angles. Factors such as ozone penetration or an unclean environment where there is a build up of waste material can also dramatically accelerate wear. Belt cleaning systems, especially steel edged scrapers, can also cause wear to the top cover surface.

THICKER IS NOT ALWAYS BETTER

The difference in thickness between the top cover and the

bottom cover should not normally exceed a ratio of more than 3:1. In theory, the more abrasive the material and the shorter the conveyor, the thicker the cover should be. In reality, the actual abrasion resistance quality of the belt cover is much more important than the thickness. Many conveyor belt suppliers offer belts with covers that are thicker than are actually necessary in an effort to compensate for the poor abrasion-resistant qualities of the belt rubber that they are using. Having belts that are thicker than really necessary can potentially cause other operational problems.

DIFFERENT TYPES OF ABRASION

It is a common misconception that a belt specified as being ‘abrasion resistant’ should naturally be expected not to wear quickly. In actual fact, because of the variety of materials that are carried on conveyor belts, there are a number of different causes of wear and abrasion. For example, heavy and/or sharp objects such as rocks can cause cutting and gouging of the belt surface whereas materials such as aggregate, sand and gravel literally act like sandpaper constantly scouring the rubber cover. For this reason, there are different types (grades) of abrasion resistant cover.

There are two internationally recognized sets of standards for abrasion, EN ISO 14890 (H, D and L) and DIN 22102 (Y,W and X). In Europe, it is the longer-established DIN standards that are most commonly recognized and accepted. Generally speaking, DIN Y relates to ‘normal’ service conditions and DIN W for resistance to abrasion, cutting, impact (from high drop heights), and gouging caused by large lump sizes of heavy and sharp materials.

To provide a longer lasting and therefore more cost-effective solution, Dunlop’s approach has been to develop a range of abrasion-resistant covers specifically designed to deal with both specific and combined causes of wear. As a result, Dunlop belt covers exceed international quality standards by a very significant margin. An excellent example of this is their RA ‘standard’ abrasion resistant cover, which exceeds the DIN Y standard by more than 50%.

For extremely abrasive and/or sharp materials, Dunlop’s RS cover exceeds the highest abrasion standard (DIN W) by nearly 30% and the equivalent ISO ‘D’ standard by more than 40%, which under normal operating conditions should directly be reflected in the working lifetime of the belt.

THE IMPORTANCE OF OZONE RESISTANCE

At ground level, ozone is a pollutant. The level of ozone exposure can vary depending on geographical and climatic conditions and is usually most concentrated in cities and coastal areas. Conveyor belts being operated in ports can be particularly affected. Scientific research has shown that exposure to ozone increases the acidity of carbon black surfaces and causes reactions to take place within the molecular structure of the rubber. This causes surface cracking and a reduction in the tensile strength of the rubber, which has a direct impact on the performance of the belt and its working life. There can also be significant environmental and health and safety consequences, especially when conveying materials such as grain because fine particles of dust penetrate the surface cracks, which are then discharged (shaken out) on the return (underside) run of the belt.

Because of the growing importance of ozone resistance, Dunlop introduced mandatory testing to EN/ISO 1431 international standards using an ozone testing cabinet some years ago and by using special additives in its rubber compounds, it has ensured that every Dunlop belt exceeds international standards by a considerable margin.

OIL RESISTANCE

Conveying materials that contain oil and fat can also have a very detrimental effect on the performance and life expectancy of a conveyor belt because it penetrates into the rubber causing it to swell and distort. This, of course, is a common problem within the dry cargo industry. Because ISO or DIN standards do not exist for oil resistance, Dunlop applies the ultra-demanding American ASTM D 1460 standard.

Oil and fat resistance can be divided into two sources — mineral oils and vegetable and animal oils and fats. Dunlop uses a very special compound formula in the ROM cover grade quality, which is specifically designed to resist the penetration and therefore minimize the damage that vegetable oils and fats can cause. Mineral oils are the most aggressive, and therefore demand a particularly high level of protection. As a result, Dunlop developed a special compound to create the extremely successful ROS cover quality.

AN OFFER YOU CAN’T REFUSE?

It is important that buyers of conveyor belts remember that DIN and ISO standards are only the minimum benchmark of acceptability. Wear-resistant covers that conform to international standards still often have to be replaced after unacceptably short periods. Despite the claims of the manufacturers and traders, laboratory tests reveal that more than 50% of belts tested are found to be significantly below the minimum standards.

The direct connection between the quality of the raw materials used to make a belt and the selling price is highly significant. Although there can never be a fixed formula due to the wide variety of individual belt specifications, a general ‘rule of thumb’ is that raw materials represent approximately 75% of the production costs whereas labour costs generally only represent around 15%. For this reason, prices that seem ‘too good to refuse’ should always be treated with considerable caution.

When a supplier is quoting a price that is significantly less than a competitor (often 25% lower or more) for apparently the same DIN or ISO-compliant specification, it is logical to conclude that raw materials of questionable quality and/or dubious origin have been used to keep that price as low as possible. In addition, materials such as essential (but costly) chemical additives needed to create vital physical properties such as ozone resistance will have either been used in insufficient quantities or most probably not at all. The chances are that the ‘irresistible’ offer will result in a belt that needs to be repaired, re-spliced or totally replaced significantly sooner than the seemingly higher-priced option.

SEEK ADVICE

What is clear is that there is a lot more to conveyor belts than meets the eye and that the days when conveyor belts just seemed to be long lengths of black rubber is certainly a thing of the past. The attraction of low prices can prove to be a very expensive mistake. As often as not, the quality of a belt is reflected by its price so it is always worth the effort to check the original manufacturers specifications very carefully and ask for documented evidence of compliance and the length of the warranty.