Customers often ask for a bag of a specific size, specifying the target weight. Products have very different bulk densities. A 1000 kg bag can have a capacity of 200 liters or just as well as 2500 liters. Therefore, the basic information when developing a specification is the bulk density of the packed product. On this basis, we can calculate the capacity of the bag for the desired total weight of the package. After selecting the type of pallet, e.g. EURO, we can determine the height of the bag.

Most bags have a load capacity of up to 1000 kg, this is the most popular value. This also results from the fact that a truck usually holds a maximum of 24 pallets, i.e. 24 bags, i.e. 24 tons. Of course, big bags are also produced with a load capacity of 1500 kg, 2000 kg or even more.

This is a safety factor. In short, it tells you how much the packaging can withstand in a tear test. SF 5:1 means that a 1000 kg bag withstood at least 5000 kg. This is the minimum factor for big bags. A bag marked SF 5:1 is designed for single use. Bags marked SF 6:1 can be used multiple times. Bags marked SF 8:1 are designed for intensive multiple use and can be repaired. The latter are rarely used.

The standards do not specify how many times a package can be used. It depends on many factors, such as: the load-bearing capacity of the package, working conditions, type of packaged material. It is important that the condition of the bags is monitored, especially around the bottom and discharge chimney. In case of doubt, it is always safer to use a new package. In the case of food packaging, an additional factor is the hygiene and cleanliness of the bag. In the case of multiple use, production batches will be in contact with each other, which may affect the quality of the product and lack of traceability. The solution in such cases may be the use of disposable foil liners. The bag can complete many cycles, while the liners are treated as a disposable barrier.

Sometimes it can happen that a big bag is difficult to empty because the goods tend to clump or get stuck in the lower chimney. In such cases, a wide discharge chimney or, for example, a cone-shaped bottom can be used. The last resort is packaging with an apron-shaped bottom. However, such a solution can be problematic in the case of goods with a high bulk density.

There are two factors that influence whether a bag is suitable for food packaging or not. The first one concerns whether the components used meet the requirements for contact with food. This is related to the content of heavy metals or the results of specific and global migration. Organoleptic properties are also important, i.e. whether the contact of the food product, e.g. with the fabric of the big bag, will not affect the taste or smell of the product. Many customers only take into account the first factor, forgetting that the conditions in which big bags are created are equally important. The production of big bags is still based on human work and manual processes, therefore there are many threats in terms of physical, chemical or microbiological contamination. Therefore, it is a necessary condition that big bags are produced in controlled conditions, where a hygiene management system is implemented. Such manufacturers work on the basis of food standards such as ISO 22000 or BRC. Only meeting these two conditions means that the packaging is safe in terms of food packaging and the big bag is a so-called food grade big bag. The packaging may meet the first condition, i.e. be made of components that are suitable for packaging food, but big bags may be produced in conditions where there is a high risk of contamination, e.g. with remnants of threads, hair, mould or bacteria.

Many food companies choose big bag models made only of fabric, often coated with sealed seams, to pack their products. This is a reasonably priced option, also appreciated in terms of functionality and recycling (such a big bag is 100% made of polypropylene). However, it should be remembered that they are not without flaws. First of all, in terms of barrier properties, it is rather primitive packaging (the elements are joined by sewing and the holes after the needles are filled with a special sealant). However, it should be remembered that they are not without their flaws. First of all, in terms of barrier properties, this is rather primitive packaging (the elements are joined together by sewing and the holes left by the needles are filled with a special sealant). Similarly, when it comes to their cleanliness, they are incomparable to packaging equipped with an liner. Especially in the case of goods with a small fraction, e.g. milk powder or starch, we recommend using bags with an liner. This is also very important in the case of packaging products that will be transported by sea or that are to be stored for a longer period of time. In such cases, the bag should be equipped with at least an liner made of polyethylene (PE). More demanding products that are sensitive to moisture (as a result, causing clumping), odours (loss of aroma), oxygen (e.g. resulting in the decomposition of fatty acids) should be packed in liners made of more advanced films or laminates that contain, for example, polyamide, EVOH, PET or aluminium. The reluctance of some customers to use liners is partly due to historical experiences when liners were placed inside bags and were just a simple sleeve. This design could cause the liner to move during packing and the liner to fall out during discharge, or, on the contrary, it could also clog the exhaust chimney. These concerns are no longer justified, currently manufactured liners are profiled in the chimneys, so their shape and dimensions reflect the shape of the external big bag. This, combined with the assembly of the liner, by gluing the liner or sewing it in, makes it an integral part of the bag. Packing such a big bag and emptying it is basically no different from big bags without an liner.

Big bags, commonly called antistatic, are those that provide protection against the negative effects of electrostatic discharges, which in extreme cases can cause an explosion during filling or emptying of big bags. Electrostatic charges accumulate during filling and emptying of big bags. If the packed product, or the atmosphere around it, has a sufficiently low minimum ignition energy (MEZ), then an explosion can occur at the moment of spark jump. Most products packed in big bags can be packed in Type A big bags, which do not provide any protection against static electricity. The factor that determines this is the minimum ignition energy. At low values ​​of this parameter (details in the IEC 61340-4-4 standard), it is necessary to use type B (antistatic) big bags or more advanced models such as type C (dissipative, which require grounding) or D (dissipative, which do not require grounding). It happens that customers use the wrong types of big bags. This is sometimes due to ignorance, and sometimes to habit ("we have always used such big bags and there has never been an accident"). It should be remembered that the fact that there has been no explosion up to this point does not mean that such action is safe.

Big bags of type B, C and D can be equipped with liners, however, it should be remembered that just as the big bag itself requires a suitable construction, the films also require a special composition (recipe). Antistatic films (including permanently antistatic) or electrostatic discharge films are usually used.

Hazardous substances defined by so-called UN codes such as the popular UN 3077 can be packed in big bags. Of course, not all so-called UN codes listed in the ADR Book can be packed in big bags, some products require, for example, rigid plastic or metal packaging. If a given substance allows the use of a big bag, then the manufacturer can design packaging adjusted in terms of volume, bulk density and target load-bearing capacity of the package. It should be remembered that the package should be fully filled. A UN-certified big bag has a stronger construction than a standard big bag, this is primarily due to significantly higher strength requirements. During certification, the bag undergoes six different tests. The most difficult of them is usually dropping the bag from a height (depending on the toxicity of the product, e.g. II or III packaging group, this height is different, the more toxic the product, the higher the required height). UN-certified bags should be correctly marked, which is also precisely described in the ADR book. It is worth remembering that some UN codes, such as UN code 3077, require the bag to be equipped with an liner. When buying bags with the UN mark, we should always check whether the packaging manufacturer has a current certificate.

Recently, it has become possible to collectively pack big bags, octabins or other large containers using vacuum or inert gases. Paktainer offers big bags, liners or hoods equipped with special valves that use technology developed by VQM packaging. It allows for quick creation of a vacuum or "flushing" the contents, e.g. with nitrogen. The aim of such actions is usually to reduce the oxygen content in the package, which results in a longer shelf life, and can radically change the technology and production processes on the customer's side. As a result of the vacuum, the customer can also maintain a significant reduction in the volume of the packed product, as well as inhibition of undesirable processes such as the development of mold or fungi. Examples of beneficiaries of these solutions are producers of e.g. coffee, tea, seeds, hemp or nuts.