Product category:
Powder and Solids Handling
News Release from: Chronos Richardson | Subject: BAGS of CHOICE
Edited by the Processingtalk Editorial
Team on 06 February 2004
Optimising semi-bulk distribution in
flexible bags
The use of flexible packaging to transport, distribute and market dry solid products has expanded rapidly over the past decade and this trend is set to continue to rise
The use of flexible packaging to transport, distribute and market products such as chemicals, minerals, foodstuffs, pharmaceuticals, animal feeds, fertilizers, grain, plastics, cement, growing media, horticultural products and building materials has expanded rapidly over the past decade and this trend is set to continue to rise It plays a vital role in any supply chain and can be used effectively for short, medium or long distance transportation by air, sea, road or rail
This article was originally published on Processingtalk on 2 Jul 2008 at 8.00am (UK)
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Flexible packaging can be a substitute for, or complementary to, bulk transportation and storage, providing fast availability of the right product at any given time - with minimum stock holding.
Flexible packaging is 'flexible' in more senses than one, offering both manufacturers and users optimum operational convenience.
The reasons for the steady growth are quite diverse; the main factors being increased globalization of manufacturing, the rapid growth of 'hub and spoke' logistics, improvements in flexible packaging technology and increased ability to meet regulations such as health, safety and hygiene.
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Wide Choice.
Products can be packaged in a wide array of bags, sacks, bales, big bales, big sacks, big bags and octabins, with typical capacities ranging from 1 kg up to 2000 kg.
A diverse range of packaging materials is available including paper, polypropylene (PP), polythene (PE), composites, jute and hessian.
The packaging has a number of important roles to play and therefore the choice of the correct type for a particular application must take into account all the relevant requirements.
These include the type and characteristics of the product, transportation methods, ongoing handling requirements and destination, product hygiene, the environment, final use of the product, market forces- including brand image- as well as health and safety and other legislation.
Packaging integrity is of paramount importance and any unwanted failures can have far reaching consequences.
Added to this is the growing importance being placed on the recycling of packaging and the costs associated with meeting legislation such as the EU Packaging Waste Regulations can be significant.
As a result, reusable packaging such as FIBCs, which do not involve secondary packaging, are very cost effective for certain applications.
Packaging Technology.
Significant improvements and innovations in packaging technology continue to play a vital role in the increasing use of flexible packaging.
In today's market, manufacturers are faced with the problems of increased legislation and greater demands from their customers, coupled with reductions in capital expenditure and pressure on earnings.
Gone are the days when companies could afford the luxury of individual dedicated packing lines for each product and they now expect to be able to package different products in different ways - all with the same line.
Equipment now has to handle diverse bagging materials in all shapes and sizes, including sacks made of paper, high-density polythene and jute.
Product line changes have to be quick and easy without problems with cross contamination.
To meet these diverse demands, equipment ranges from individual filling stations, up to fully integrated high speed bagging lines incorporating peripherals including automatic bag placers, bag stretchers, de-aerators, sealers, stitchers, conveyors, palletisers and shrink wrappers.
De-aeration.
Filling bags and FIBCs with powders presents a number of challenges.
Entrapped air makes bags balloon and therefore difficult to handle and stack.
There are number of proprietary methods employed to remove the air and maximise product density.
One system uses a patented shockwave technique, which removes the air before filling by alternately subjecting the product to vacuum and then atmospheric pressure.
This process using pressure waves increases the density of most powders to their maximum packed density in a single cycle, without damaging the product.
This is especially effective with traditionally difficult products such as Titanium Dioxide, calcium carbonate and fluffy carbon black, with bulk volume reductions of over 60% being possible.
Optimising semi-bulk transportation.
Palletized Bags.
The most expedient way to provide effective handling and transportation for bags up to 50 kg is to stack them on pallets.
As result, automatic palletisers are a vital part of any bagging line and ensure safe and expedient loading of bags onto a wide range of different pallet types.
In a way, shrink wrapped pallets can be seen as compartmentalised big bags.
Palletisers fall broadly into three categories, robot, low level and high level.
In addition there are compact palletisers, which use a combination of robot and traditional palletising technologies and of course manual techniques.
The choice depends on factors including product characteristics, product throughput speed, available budget, space limitations, point of sale considerations and required flexibility.
Optimising the stacking of bags on a pallet must also take into account the bag shape and configuration.
Robot palletisers.
The use of Robot palletisers is growing steadily and they offer optimum user flexibility for many lower speed applications.
They take up less space than most fixed palletisers and are ideal for palletising speeds of up to 800 bags an hour (this may increase to over 1000 bags per hour under ideal conditions).
Robot palletisers are very effective for palletising bags coming from more than one bagging line, especially if the bags are different sizes.
They can also handle different types of containers as required and are effective in stacking bags inside boxes and containers.
Low level palletisers.
Low level palletisers provide a cost effective and space efficient solution for lower speed applications.
The bags are transported via a low-level infeed conveyor and the layers are formed directly on the pallet.
High level palletisers.
High level palletisers provide the fastest speeds.
For small 1 kg bags, speeds of up to 9000 bags an hour can be achieved while even for 25 kg bags, rates of 5000 bags an hour are achievable.
These speeds are achieved by ensuring a continuous process without bottlenecks.
Complete layers of correctly orientated bags are formed on the layer table before being is pushed onto the pallet, which in turn descends as each layer is added.
The perfect palle.
For efficient palletising, correct bag orientation and positioning is vital, especially with non-uniform bags.
If bags have uneven product distribution or include lifting handles for example, slight overlapping of the bags ensures optimum packing density and pallet stability.
Compact palletisers are ideal for this process where the robot gripper technology allows precise positioning of the bags.
When palletising bags with formed seals, the bags can be orientated so that these folds or seams face towards the middle of the pallet.
This gives smooth clean outside faces to the pallet and ensures that any product spillage from seal failure is contained within the pallet pile.
Another important process in the palletising sequence is to ensure the bags and individual layers are uniform in shape and size.
This can be achieved by first flattening the filled bags as they come from the filling line by means of a bag pressing device.
The bags are then correctly orientated and made up into layers.
Dams incorporated in the layer-forming unit then compact the layer laterally on all four sides.
The layers are formed in alternate interlocking formation to give optimum pallet stability and after loading, the complete pallet can be further compressed.
For small bags, layer formations may contain up to 72 bags, while for bags from 5 - 50 kg typically layers are made up from three to ten bags to suit either standard euro or customer- specific pallets.
Palletisers are available, which can recognise different products coming into them from two separate lines.
As the bags arrive, they are identified via their bar codes and the palletiser automatically selects the correct pallet type from the pallet magazine.
Palletising bags is only one part of the logistics equation.
Where appropriate, palletisers can be adapted to work in reverse and take bags off pallets for distribution within the process.
Bales.
When packaging compressible natural or synthetic products such as growing media, wood shavings, animal bedding, kevlar and cellulose, ensuring maximum bag content density is an important factor, which impacts on storage space and freight costs.
Automated baling machines provide an ideal solution and finished bale compression ratios can be as high as 30:1.
A hydraulic ram is used to compress the product to the desired compaction before the bag is folded and sealed.
The finished bales have square sides and edges, making them stable and easy to stack or palletise.
Use extensively for bales of 75-200 litres, the technology has now been extended to produce larger semi-bulk bales with compressed volumes of over one cubic metre.
These can be stacked one on top of the other to maximise transportation.
FIBCs.
Flexible Intermediate Bulk Containers have been in use now for almost half a century and it is now estimated that over a quarter of billion tonnes of product are transported in FIBCs throughout Europe every year.
The term FIBC is primarily used for describing so called' big bags' or 'bulk bags', with capacities typically up to three cubic metre and load capacities ranging from 500 to 2000 kg.
Although their initial cost is relatively high, 'big bags' are designed to be reused a number of times, especially in closed circuit systems, where problems of control logistics, prevention of contamination, cleaning, safety issues and liability for loss or damage can be defined between the shipper and receiver.
Other important future considerations are the costs associated with meeting the EU Packaging Waste Regulations.
Big bags are transported by carrying loops and therefore do not usually involve pallets or secondary packaging, which is becoming increasingly expensive to recycle.
The bags themselves can be recycled and after use they can be automatically flattened to minimise shipping costs.
The standard diameter of FIBCs is such that two bags can be fitted across a lorry or shipping container and specially configured containers are available to suit the shipping of FIBCs.
When transported by ship, FIBCs can be 'gang-loaded', with up to 14 bulk bags on a spreader bar and in this instance they are classed as break bulk.
Versatility.
Most of us are familiar with the basic open type big bags we see at DIY superstores and builders merchants, used for delivering sand and gravel.
However the available options are extremely diverse and the scope of FIBCs can be significantly broadened by the use of specifically designed inner and outer liners.
One of the main purposes of these barrier liners is to maintain the chemical and physical properties of the product by providing protection against oxidation, moisture ingress and toxic spillage whilst also preventing odour transfer or other contamination.
There is a wide range of liners available, including open top with conical bottom, filling spout with conical bottom, open top with flat bottom, filling and discharge spout.
The designs take into consideration storage and transportation conditions and, where appropriate, liners can be replaced after each use.
The materials used for liners are as diverse as their designs and include LDPE compounds, multi layer compounds such as PE-PA-PE, solvent free aluminium compounds, black conductive compounds, and laminated foil.
One recent innovation combines micro-pored PET and PE film with aluminium, which provides excellent static electricity control without product leakage.
The patented micro-perforation process allows static charge to penetrate the insulating plastic layers before being carried to ground via the aluminium layer.
Safety.
Safety is an important issue, especially given the 'global' nature of FIBCs.
Clear guidelines on a range of safety issues have been established by associations such as EFIBCA, FIBCA and PIRA.
Bags used for hazardous materials are required to carry the UN mark and meet their requirements for the Transport of Hazardous Goods.
Unfortunately this is very much open to interpretation and different countries have their own national rules.
Therefore, at the end of the day, safety often depends on a voluntary code of practice, adopted and policed by the bag manufacturers, shippers and users themselves.
Many FIBCs are filled and discharged in dusty environments and equipment used must meet the statutory health and safety regulations including ATEX.
The bags themselves must also meet strict requirements to avoid them being the source of any potential sources of ignition.
Peripheral Equipment.
As the use of FIBCs increases, so does the range of peripheral equipment for filling, discharging, handling and transporting.
As with any packaging process, key issues are speed, accuracy, flexibility, safety and cost.
Equipment includes mobile discharge stations, automatic pallet dispensers, de-aerators, automatic bag flatteners and folders.
Octabins.
Although FIBCs are extremely versatile and cost effective, an alternative container is finding increased application in the food and chemical industries.
Cardboard octabins are now widely used especially in the plastic resins industry and offer certain advantages over FIBCs.
Octabins can be described as semi-flexible intermediate bulk containers.
As the name suggests, these containers have eight sides and resemble giant hatboxes.
Although made of card, they are extremely durable and can be used for capacities up to 2000 kg in widths up to 2000 mm.
An inner sleeve or liner is typically glued and stitched to the container Before and after use, the sides, bases and lids can be transported and stored flat.
Once assembled they provide an extremely light yet rigid container and, as with FIBCs, a variety of special liner inserts can be used to provide specific protection for products.
Unlike FIBCs, which can be difficult to stack, the shape and rigidity of octabins makes them safely stackable.
Filling octabins is very straightforward and there is no need for special support frames.
Once the octabin has been filled, the liner evacuated and sealed, the product is free from contamination or moisture.
The addition of free-flow bases to standard octabins allows them to be discharged from underneath their support pallet.
The bases come complete with a polythene control valve to regulate the discharge rate.
If the product is likely to settle during transit and storage, two piece telescopic octabins can be used.
After filling has taken place, the top sleeve is released to settle onto the top of the contents, thereby avoiding any unwanted void in the top of the bin.
Conclusion.
Effective flexible packaging is becoming an increasingly important part of any manufacturing process.
The advances in technology, coupled with improved world-wide logistics, are providing important benefits for both manufacturers and users of bulk materials.
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