Innovative conveying solutions
May 15, 2013
Several of the innovated bulk-solids handling systems used in other industries can be used by the grain handling industry. This article will look at some of those interesting and innovative handling systems.
The RopeCon: A high-tech Austrian system that combines rope technology to transport people and loads on hanging ropes with conveyor belt technology. The conveyor system allows passing over geographical obstacles such as rivers, roads, buildings, valleys with spans of up to 1,000 meters between supports, in one section.
The Pipe Conveyor: A Japanese design that overcomes several problems, including spillage of material, belt training, limited horizontal and vertical curves, and limited angles of incline. The open belt passes through a series of transition idlers to form a pipe shape, making it fully enclosed for the length of the conveyor.
The Manutube: A design from France that includes an enclosed belt conveyor with a belt running inside a plastic tube with no idlers, fully enclosed.
The Overland Conveyors/Curvoducts: A design also from France that is effective for very long distances with horizontal curves of low radius.
All of these systems are designed to minimize dust emissions, reduce environmental challenges, improve safety and reduce costs.
When a project includes a difficult layout, with long distances and/or many obstacles on the way, such as buildings, tanks, roads or even rivers, valleys, hills, etc., a conventional solution is very difficult to implement. If the material also is difficult to handle, such as very corrosive, hygroscopic material, or even toxic products with strong environmental precautions that need a dustless solution, creative and innovative solutions are needed.
A first solution that is usually more expensive in the long run is going back to systems of individual loads in trucks. The use of continuous bulk handling systems is usually driven by lower operational cost, as opposed to systems such as trucks which have lower initial capital but much larger operational costs.
In general, the longer the distance and the higher the capacity, the more likely it is that a continuous system will be the most effective option. Sometimes many large deposits with a relatively low price per tonne become not feasible if they are too far away from the port terminal or rail line. This article will review the new, different types of continuous transport systems and the factors that influence their selection.
Troughed conveyor belts are the most widely used continuous transport system for bulk materials. Since their inception in the beginning of the 20th century, they have grown enormously in length, installed power and capacity while reducing their specific energy consumption. Their main disadvantage is their limited ability to achieve vertical and horizontal curves. This ability is reduced as capacity and belt tensions increase. Main applications are in the mining industry, where belts would allow for very long flights without intermediate drives. The length of individual sections is limited by economic reasons, as the savings on transfer stations are neutralized by the additional cost of the high-tension belts.
There are installations in the mining industry with capacities achieving 40,000 tonnes per hour (tph), but long-distance conveyors are normally limited to 25,000 tph. In the mining industry, the products handled have high densities: between 1.5 to 2.5 tonnes per cubic meter, which is twice or triple the grain density.
Developments in belt fasteners technology allow the use of high-tension belts, with large installed power. Better understanding in the design of belt conveyors and their dynamic behavior and loading systems have allowed the use of faster belts, with successful references of up to 8.5 meters per second for overland conveyors.
TMSA in Brazil is installing a belt conveyor of 20,000 tph for iron ore (density 2.20 tonnes per cubic meter) and 3,100 meters long for Porto de Açu, a huge port terminal in the Rio de Janeiro state. TMSA is working with France-based RBL-REI, which has much experience working with long conveyors with curves, for what they call “Curvoducts.” RBL-REI just finished in China, what it considers the longest belt conveying system in the world — 40 kilometers in only three sections of 10 kilometers, 13 kilometers and 17 kilometers.
In the agribusiness industry, there are not projects with as long of conveyors as the mining industry, but there is a need for solutions exceeding 1 kilometer.
Pipe conveyors overcome several of the problems commonly associated with conventional conveyors, such as spillage of material, belt training, limited angle of incline, horizontal curves and multiple flights.
There are well over 1,000 pipe conveyors in the world. Invented in the early 1980s and known initially as ‘Japanese Pipe Conveyors’ (JPC), owned by Bridgestone Japan, the technology is mature and applied to a variety of applications.
The conveyor resembles a conventional troughed conveyor at its tail end where the material is loaded. The open belt then passes through a series of transition idlers to form a pipe shape which is maintained for the length of the conveyor. Just before the discharge pulley, the belt opens up again and allows the material to be discharged in the normal fashion. On the return side, the belt is again formed into a pipe shape.
The material being transported by a pipe conveyor is fully enclosed by the conveyor belt for the major portion of its travel. This has several benefits including minimizing environmental pollution as dust generation and spillage are eliminated; protection from outside contamination and possible theft; and product can be transported in the return pipe.
Pipe conveyors are able to do tight vertical and horizontal curves. A single pipe conveyor can thus replace several conventional belt conveyors, reducing the need for multiple transfer points, the power needed to lift the product, degradation of the product and dust generation at transfer points and costly chute liner replacements. Pipe conveyors can also operate on vertical inclines of up to 30 degrees.
The main disadvantage of pipe conveyors is their cost in many applications and their higher power consumption when compared to conventional conveyors. The longest pipe conveyor in operation is 8,200 meters long.
In past years, typical capacities ranged between 100 and 1,000 tph, but today there are several systems above 2,000 tph in operation. TMSA in Brazil has supplied pipe conveyor systems for a thermal power plant of 2,400 tph of coal in four sections totaling 7,115 meters long and in an export port terminal handling 2,400 tph of alumina.
Developed during the 19th century, ropeways were widely used before the advent of the conveyor belt in the mining industry. Today, they still hold a niche on transport in a high-slope landscape, where civil works and supporting structural requirements are more expensive than the requirements of a ropeway. Installations achieve capacities of up to 1,500 tph for bulk materials with single loads of up to 50 tonnes. Rope spans between support towers can be achieved up to 3,000 meters.
It’s an old technology that becomes a new solution, with quick loading and unloading stations.
RopeCon is a new technology developed in recent years by Doppelmayr, of Austria, a world market leader in ropeways. The RopeCon is a bulk material and unit load handling conveyor which combines the benefits of well proven technologies: the ropeway and the conventional conveyor belt (hence the brand name RopeCon). A flat belt with corrugated side walls and integrated wheel sets runs on anchored track ropes guided over towers. The hauling function is performed by the belt.
Main features of the RopeCon include conveying length up to 30 kilometers, conveying capacity up to 25,000 tph, vertical rise in one section up to 1,000 meters, inclination of more than 60 degrees and belt speed up to 8 meters per second. The tower spacing can reach up to 1,500 meters.
The RopeCon operates off the ground, thus minimizing space requirements and easily crossing buildings, roads, rivers or other obstacles. The top of the support towers is attached to the track ropes, and at the bottom hinges are mounted. Top and bottom belts each run on two track ropes. Full-locked coil ropes act as track ropes (support function). Drive/tensioning equipment is in the loading or unloading station.
This combination of the technology of cable transportation with the simplicity of a conventional conveyor is a merging of two technologies that result in an incredible system that looks like a “flying carpet,” having the ability to overcome rough terrains and difficult obstacles.
The RopeCon system should not be confused with the ‘Cable Hauled Belt Conveyor,’ developed in the 1950s. In this system the belt just sits on steel drive ropes that move and are supported by regular intervals along the conveyor route by grooved pulleys or fixed wheels (an equivalent to idlers) that turn but do not move.
The RopeCon system is the opposite: the cables do not move but are fixed, under tension, working as a rail, and the wheels, (working as an equivalent to the idlers), roll on the steel cables.
Manutubes are a dustless conveyor technology, which consists of a belt conveyor, fully enclosed, transporting material through a plastic tube. The belt slides inside the tube with no idlers, generating a natural airflow. It is a dust-tight technology that can guarantee less than 1 mg of dust per cubic meter of air, for cleaner working area and longer lasting equipment.
They come in different versions with belt return open with protection grid or belt return totally closed and return casing with a dust cleaning/reclaiming system. Manutubes are particularly adapted for applications involving powders or dust generating materials. Capacities vary from 10 cubic meters per hour to 3,000 cubic meters per hour.
The configurations are infinite: self-supported, curved on a vertical plan, inflected, and with or without walkways.
Main features include a belt conveyor with no attrition on the product; reliable transfer for bulk material with proven sealing capabilities; transfer of dangerous material with no environmental contamination; dust level control; controlled inner atmosphere, if necessary; mastering of explosion risk by dust, hygrometry and oxygen control.
Manutubes are optimum for conveying fragile, corrosive and hygroscopic products. The equipment is lightweight with no idlers that can be used at inclinations up to 60 degrees. Free span between supports of up 50 meters is possible and no sidewalks are needed.
Because they have a low number of moving parts, maintenance is easy and inexpensive. The half-tube trough shape provides for transport of higher volumes for the same belt size. Most versions are designed for difficult, high-care and high-value products. Other versions are used for bulk commodities in place of traditional conveyors for the low maintenance, reliability and proven confinement.
The Manutube conveying system for bulk products, together with flat surface hoppers with a flat-surface feeder, developed by ABSAM Engineering, of France, are also used for loading trucks, ships, barges and railcars.
Stackers and ship loaders with counter balancing weights allow a high overhang. A hydraulic pump with power engine (electric or thermal) allows an easy setting of the inclination according to the ship loading level and tides, with a maximum angle of 35 degrees.
Different options can be added, including: “Concorde” nose, directional wheel, automotive main wheels, telescopic chute, decompression housing, and a material projecting device.
The surface hoppers, which can be mobile or fixed, combined with the flat-surface feeders and the Manutube enclosed belt conveyors, will change future designs of the reception pits, avoiding underground hoppers with expensive civil works.
It is difficult to make a simple comparison between alternative technologies, as the factors that influence their performance are extremely dependent on each application. However, a few key parameters can be analyzed to show indicative comparisons. Conventional belt conveyors and Ropecon’s have a clear advantage in the large capacity range.
Many factors determine the capital cost of a conveying system. The most important factor is the type of system to be used. If you consider only mechanical and structural elements over a relatively flat terrain with a moderate inclination and no curves, the conventional trough conveyor belts present a clear cost advantage. On similar systems, this cost advantage tends to increase as capacity increases.
Pipe conveyor belts are more competitive when you have several curves of short radius and you need to avoid transfer points and spillage. The Manutube is the solution to convey capacities up to 2,000 tph and materials with explosion risks, contamination risks and strong environmental issues.
Civil and earthworks costs must also be considered. Depending on the terrain profile and soil properties, the civil works can be a determinant factor in the cost equation. There are projects located on difficult terrain, with large earth movement requirements and poor soil conditions, where the civil cost can be more expensive than the design and equipment supply cost.
The need to use elevated structures to allow free passage of people and/or vehicles or to deal with flooding and drainage issues can also influence the decision of the type of system to be used. In this type of application, the ability of pipe conveyors and the Ropecon system to adapt to difficult terrain might be decisive when choosing the best alternative. The Manutube, due to its lower weight, allows spans of 50 meters and lighter support structures.
In any of the alternatives, the use of single flights normally presents the lower capital and operational costs when transfer stations can be avoided.
Transfer points are very expensive, generate wear and tear in belts, require support towers, electrical controls, more energy consumption and dust control systems.
Manutubes reduce and simplify transfer points, as they do not need dust control, can go steeper with up to 60 degrees inclination, and are lighter units, with less support towers. They can weigh half of the conventional conveyors, allowing bigger spans between towers.
Pipe Conveyors can reach up to eight kilometers and can avoid transfer points due to their capability of curving the conveyor.
Overland/Curvoducts, in long routes, above one kilometer long, have the ability to curve and follow the lines of minimum land inclination, reducing the number of transfer points and civil works.
The main advantage of continuous systems is the lower operating cost when compared to discontinuous systems such as trucks. A large part of the cost is constituted by the power requirements.
Pipe conveyors present higher power consumption when compared to conventional conveyors due to the increased number of idlers due to the higher forces involved. But the fact that it is enclosed and reduces transfer points provides a savings.
Manutubes have fewer moving parts. The belt slides inside a plastic tube so there are almost no idlers — only in the head and tail sections.
Ropecon systems and ropeways present the lowest specific power consumption among the alternatives compared, an average of one-third of conventional conveyors.
For the Conventional Belt Conveyors, including the Overland Conveyors, progress has been made in recent years and better designs present power consumption significantly lower than older installations. They need heavy steel support structures with towers spaced 25 to 30 meters.
Maintenance along the conveying routing is normally associated with spillage and material carry back. In this regard, Pipe conveyors, Manutubes and Ropecon present a lower maintenance requirement than conventional conveyors. Ropecon systems are virtually maintenance free along the conveying route. Operational costs can be 10 to 15 times less than conventional systems.
Ropecon systems require little intervention in the landscape on undulating terrain or when obstacles such as buildings, roads, tanks, and rivers are involved, and are considered having the minimum environmental impact, as they pass over these obstacles. The presence of fugitive material, dust emission and spillage can be the most damaging environmental impact, depending on material transported and location of the system.
Manutubes and pipe conveyors, with their totally enclosed transport system, are frequently the best alternative when transporting fine and/or contaminating materials in sensitive areas.
A Ropecon system can be supplied fully enclosed with special covers, adding this feature to all the other advantages.
Reliable and sustainable operation, with maximum safety, can be obtained with any of the systems discussed. The issue is the selection of components and design of auxiliary and safety systems that are similar for all of them. Some systems have better proven sealing capabilities, especially in the handling of dangerous materials with no contamination of the environment and, if necessary, under controlled inner atmosphere.
The mechanical advantages of each system depend greatly on the number of moving parts, thus easy and cheaper maintenance can be achieved. A Ropecon has one-fourth or one-fifth fewer moving parts than conventional conveyors. A Manutube has about one-third fewer moving parts.
Most of the presented systems are specially designed for difficult, high-care and high-value products. Some versions are used for any other bulk material in place of traditional conveyors for its low maintenance, low operational costs, reliability and proven confinement.
A major evolution has been undertaken in recent years, mainly in the application of technologies from other industries by the grain handling and processing industry. Some of these technologies could replace conventional conveyor belts, while other technologies might not replace belt conveyors, but rather complement them under specific conditions.
The proper selection of a conveying system has to be done by a proper analysis on a case-by-case basis, which includes cost but also the mechanical/structural aspects of the project, operational costs, environmental and social issues, civil works and land access.
It is very inspiring to see what other industries do and how other far-away professionals solve the same problems. It is a good way to grow and improve, looking outside the box.