Before designing a big bag, we need to specify its structure, which will help answer the following questions:
1) What raw material will be transported in it?
– type – physical state, fraction, volume, weight 1m3, weight in the SWL bag – required internal dimensions of the bag, ease of spilling / emptying, for food purposes, possibility of explosion under the influence of electrostatic discharge, whether it is a dangerous raw material – UN standard.
2) How many times will the bag be used and will it be stacked during storage – how yes, how many times or how many layers of storage?
3) Mode of transport and amount of storage space – can the bag stick out of the pallet outline (depends on the fraction and state of aggregation of the raw material?
4) Method of loading the bag with raw material – the method of backfilling, hanging (forks of the trolley, charging station) – by manual filling, tubular backfills – as in which diameter and length, other
5) The method of unloading raw material from the bag – manual, pipe dumps – as in which diameter and length, other.
6) Is there a need to provide additional protection for the hopper or dump.
7) Others – e.g. size, quantity and location of the document bag, printing on the sides of the bag – quantity, pattern.
Answers to the above questions will allow you to design the bag:
Ad. 1. Fabric selection – coated / uncoated / openwork / electrostatic
- fabric weight
- grade (I / II)
- lifting tape lifting capacity
- the need for a seal
- width / length and method of cutting elements – initially or one, two or four-sling sack
- Label information and UN certification
Ad. 2. Choice of fabric cont. – coated / uncoated / openwork / electrostatic
- fabric weight
- safety factor SF
- possible additional reinforcements and safeguards
Ad. 3. The need for stabilization barriers.
Ad. 4,5 and 6. Method of bag construction:
- top / top construction
- bottom / base / bottom construction
- number of slings / handles / ears
- flat fabric or sleeve
Ad. 7th Size, number and places of placing bags for documents, printing on the sides of the bag, etc. Bags must be made according to European standards, e.g. ISO 21898 standards based on tests and relevant certificates.
Materials, construction and design.
All categories of big bags should be made of flexible materials with written specification. The big bag manufacturer should have an authorized certificate of compliance for each batch of materials.
The properties of materials can be modified by adding additives to increase the resistance of materials to e.g. destruction by heat and sunlight, and to reduce the effect of electrostatic properties. All materials should be tested for breaking strength according to relevant international standards and should be able to withstand at least 85% of the original
breaking strength after complete immersion in water for 25 +/- 1h. This measurement should be taken after the first drying of the test sample, and then conditioning it for 60 +/- 5min at 23 +/- 2 degrees Celsius and relative humidity 50 +/- 5%.
All big bag carrier materials after testing in accordance with the test described in Annex A shall retain at least 50% of the original breaking strength and elongation of the materials. Materials should be selected and combined in such a way that
it was possible to repair them.
All seams and joints should be finished by closing or reversing sewing (sewing back) or finished with a 20 mm “tail”. All seam ends should be secured. Surfaces attached by welding, gluing or welding should be clean.
Designing the height of the big bag.
The designed height of the filling should be within 0.5 to 2 times the short horizontal dimension of the big bag.
In the case of a big bag with a circular cross-section, the shorter horizontal dimension is the diameter of the base of the big bag. In the case of a big bag with a rectangular base, the shorter horizontal dimension is the shorter side.