Full Line Conveying and Packaging Considerations

To succeed in an international environment, suppliers of aggregates, and products that incorporate aggregates, need high-capacity equipment that guarantees long service life, even under extreme conditions. Cost-effective transport of bulk goods involves many different scenarios – such as conveying coarse-grained material through rugged terrain from the quarry to the factory grounds, moving hot materials from a kiln cooling system to a silo and effectively packaging these materials using machines capable of delivering high levels of uptime and productivity.
    
Selecting the right equipment for these tasks calls for considering key technical and system criteria – for both the individual systems, and also how well those systems can be integrated together to maximize the overall effectiveness and performance of your operations.
    
Equipment reliability and individual component integration issues can create unnecessary risk and downtime. Component integration problems can pose serious risks to the operation, resulting in downtime, and thereby affecting the bottom line.
    
There are advantages to assessing not only the performance of the individual systems required to move raw material from mine or quarry to finished container, but also how that equipment works together as a complete solution. This is especially critical when new conveying and loading or packaging equipment is being implemented — the longer it takes for all the pieces of the system to work together fluidly, the longer it is for processors to begin earning returns on their capital investments.

Complete Bulk Materials Transport Solution
A complete transport solution will incorporate two types of systems: The means to move the input materials through processing, then package the final product once it's produced. Input materials are typically stored outdoors, in silos, or are in the source quarry or mine. These materials, in their raw and crushed form, are conveyed to the location where they will be processed – and both conveyors and bucket elevators are usually used to accomplish this task.
    
Once the aggregate or bulk product has been processed to final form, it is packaged via an automated process. There are a range of fully automatic packaging systems used for this process: Empty bag placer, bagging machine, bag cleaner, check weigher, palletizer, and pallet packaging machines. Systems will vary depending upon the application. Each of these machines really function as components in a complete processing system, transporting raw and refined materials between different processing systems, until the finished materials are ready for packaging, as well as interacting with the manufacturer’s processing equipment.

Transport Equipment Options
Many aggregate producers use components like heavy-duty conveyors and bucket elevators for the transportation of bulk materials used in their process. It is essential that these systems work well together and are of high quality.
    
Three types of conveyors are in wide use in aggregate transport applications: Overland belt, pipe, and apron.

Apron: Typically used to carry hot clinker material from rotary or vertical kilns to a silo, with inclination angles of up to 45°, and up to 60° in extreme cases. Apron conveyors are designed with overlapping and reinforced steel cells, preventing spillage during transport and discharge. They are typically moved by single or dual chains. For extreme long-distance and high lift applications, or when increasing capacities in existing systems, steel cable reinforced belts are utilized due to their high speed capabilities.

Overland belt: In principle, overland belts are regular troughed conveyors, but they’re specifically designed to negotiate around obstacles on their way from source to plant. Whereas a series of single straight conveyors need transfer towers with dust collection occurring at each, the overland conveyor carry the bulk materials on a single belt through vertical and horizontal curves, thus eliminating material transfers and excavation work along the way. Curved overland belts have reached distances of more than eight miles, carrying thousands of tons of rock around or over hilly terrain to the final destination.

Pipe: Pipe conveyors are utilized for the same purposes as overland belts. However, when severely limited with the curvature or steep angles for the system is limited, or for in-plant transportation, then pipe conveyors are the preferred choice of transport. Due to their closed top and bottom belt line, the pipe conveyor protects or prevents material to be exposed to the open environment.      

The other critical transport system commonly found in bulk material and aggregate operations are bucket elevators. These systems are ideal for transporting fine grained and coarse materials vertically in excess of 200 m. Central chain elevators are typically used for handling for very hot, abrasive or granular materials of up to 80 m, while belt elevators handle fine grained materials up to 200+ m. Coarse materials are typically fed into bucket elevators by belt conveyors, while fine materials are fed by air slide conveyors.
    
The design, engineering and “ruggedized” elements of these systems need to be carefully considered, to ensure they deliver high uptimes and long service life. The use of high-quality components fabricated for use under demanding conditions is important: Some suppliers secure the buckets to the belt using forged segment mountings. This ensures even weight distribution of retention forces in the belt. Belts are typically reinforced with integrated steel wires that can be extended endlessly by heavy-duty mechanical splices. Coarse materials are typically fed into bucket elevators by belt conveyors, while fine materials are fed by air slide conveyors.
    
Apron conveyors and bucket elevators are equipped with safety devices, such as speed control, belt alignment, and overfilling protection, but they are controlled by the main control system of the plant. Overland conveyors usually have their own integrated controls because of their complex functions.    

Packaging System Considerations
Once the materials are processed into finished product, they must be packaged. This step is crucial: After the product is processed, it is in its highest value added state. The proper packaging and equipment will ensure that it reaches the customer in that same state.
    
Bulk and aggregate material--whether coarse or fine--is often packaged in a variety of bag, constructed of different materials and in a range of dimensions. Examples of typical materials bagged are finished cement products and concrete mixes. Bagged products usually go to smaller contractors or home improvement stores. Bulk materials usually go to main construction sites or ready mix concrete plants.     
    
Three widely used bagging machines are valve bagging and form-fill seal and bulk bags packaging systems. Typically bag weights for valve bags are up to 100 lb, form-fill seal up to 50 lb, and bulk bags up to 2000 lb. Valve bagging machines were designed for industries with fine grained and abrasive materials which require high filling rates.
    
Valve bagging machines designed for highly automated, high-speed bagging will have features such as automatic weight adjustment controls per spout and self-cleaning and de-dusting systems. Valve bags are made using Kraft paper. At very high capacities, the filling is accomplished by rotary bagging machines. Bag applicators shoot the bags onto an empty spout. The bag is filled by weight while rotating, and then discharged onto the conveyor traveling to the palletizer.    
    
A form, fill, seal (FFS) bagging machine easily handles abrasive materials, special flow characters, and low dimensional stability, such as sand. FFS bags are usually made of PE or PP plastic material and come from a roll of tubular film attached to the machine. The FFS machine retrieves the required length, seals the bottom, fills the material, and finally seals the top. These types of packaging machines also feature integrated weighing units to ensure filling accuracy. Its robust design extends maintenance intervals, a necessity for the aggregate industry.

Palletizing Systems
Once the product is filled the bags need to be efficiently stacked onto a pallet. Strong, stable pallets are essential for ensuring that the packaged material can be safely shipped to end-user customers while retaining its full value. The typical pallet building machines fall into two broad categories: Palletizers and robotic pallet builders. Robotic systems are ideal for small areas and provide a lot of flexibility as they can be easily retooled or reprogramed for handling different product sizes. Typically used for lower throughput rates (up to 1400 bags/hr), robotic pallet building systems can be fitted with different product grippers for a wide range of applications.
    
Palletizers are designed for high throughput rates, up to 5600 bags/hr, while providing gentle bag handling and high stack quality. Typical robot pallet building machines handle one or two bags at a time, at a lower speed, without layer compression. In contrast, palletizers can handle many bags at the same time, at a higher speed, compressing each layer, and therefore creating better stack quality.
    
While some pallets can be shipped without further processing, it is also common to wrap completed pallets prior to shipping, which helps improve stability and provides product protection from the environment. Whereas stretch wrapping provides somewhat of a sealed cover, a stretch hood is totally sealed and is tamperproof. Hooding can also be done at a much higher speed. There are a number of pallet wrapping systems in use. However, a more recent advance on this technology is the pallet stretch hood system.
    
With stretch hooding, a single layer of plastic film tubing, smaller that the dimensions of the load, is stretched open above the load and pulled down over it. With this method, greater load stability, weather protection, intrusion protection, and improved aesthetics are some of the benefits.

Selecting the Right System Provider
With all of these components on a single line, it can be a complex and timely process to manage and source them from multiple vendors. There is also risk to the operation from extended downtime due to unforeseen integration problems. If possible, there are advantages from sourcing these systems from an overall supplier with experience integrating the systems.
    
Key capabilities to evaluate when selecting a total transport and packaging systems vendor can include:

What percentage of major components do your prospective suppliers produce themselves? If they produce all major components in house, this reduces an integration risk when introducing different products from various suppliers.

Demonstrated system reliability is crucial – what are the typical uptimes and maintenance intervals for systems that the vendor has installed?

Long-term durability should always be factored into a purchase decision.
What kind of product testing and validation processes does the vendor use? If a vendor can validate each product prior to shipment, this can help you reduce downtimes, faulty parts and unnecessary costs.

A vendor with an ISO 9000 certifications will be committed to quality management by increasing productivity, reducing unnecessary costs, and ensuring quality of all products and processes

What type of after-sales support is provided? These are complex systems, so the ability to supply in-house service contracts and domestic technicians is important to evaluate, including technical hotline support 24/7 year-round. Full customer training should be offered to ensure fully effective handoff once installation is complete

Conclusion: Focus on Complete Solutions
Converting bulk and aggregate material from raw mine or quarry source material into finished, packaged products palletized for transport to customers is a complex process that involves moving heavy, difficult-to-handle materials through multiple steps in an efficient and productive manner. There are significant advantages to treating the transport and packaging of these materials as a single, integrated systems challenge and then selecting equipment that has the demonstrated ability to be seamlessly integrated and operated as a complete solution.
    
Anthony Branch is Director of Sales, Palletizing & Packaging, BEUMER Group, Somerset, NJ. For more information, call 732-893-2800 or visit www.beumergroup.com.

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