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The current problems in the design of domestic FIBC

The current problems in the design of domestic FIBC

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  • Time of issue:2021-08-10 16:09
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(Summary description)In the planning of FIBC, from the selection of original materials, formulas, weaving, to the distribution of the force structure of the whole bag and sewing planning, especially the rules of commodity

The current problems in the design of domestic FIBC

(Summary description)In the planning of FIBC, from the selection of original materials, formulas, weaving, to the distribution of the force structure of the whole bag and sewing planning, especially the rules of commodity

  • Categories:Company news
  • Author:
  • Origin:
  • Time of issue:2021-08-10 16:09
  • Views:
Information

In the planning of FIBC, from the selection of original materials, formulas, weaving, to the distribution of the force structure of the whole bag and sewing planning, especially the rules of commodity aging, all are linked to the quality and competitiveness of negotiation. The following points are particularly prominent. The design of my country's FIBC companies should pay attention to the articles I have written (the following key points should be paid attention to in the design of tonnage bags), these factors are essential to the design of high-quality FIBCs!

1. For the safety factor

"Safety factor" is the ratio between the maximum capacity of the product in the experiment and the extra planned load. It refers to the maximum load that the container bag can withstand before it loses its function. It is indispensable in the planning of FIBC, and it is decided according to the use of the commodity and the environment of use. Within a certain period of time, provide important skills to ensure the safety of internal goods and hoisting workers. The safety factor has an important internal connection with the structure of the bag body. It changes with the influence of the bag body's own strength, planning structure and material formula. The setting of "safety factor" in similar standards at home and abroad is usually 5 to 6 times.

The national standard GB10454-2000 "Film Bags" mentions the question of "safety factor", but the degree of attention is worth discussing. The specification is in clause 5.5.1: "Periodic lifting experiment", the rule "fill the contents evenly into the container bag to full load, hang a load equivalent to 2 times the maximum load, limit the use of the bag 70 times, one-time Use the bag 30 times and increase it repeatedly. Whether the container bag is qualified or not, firstly depends on whether the contents and the bag body are abnormal, whether the connecting part is damaged or not, it means that this experiment has been passed."

In clause 4.3, the rule "the safety factor of the pulling force of the sling and sling is 6". In this way, the product has gone through the final experiment in all experiments subject to 3 times the extra load. Then, in a relatively (shorter) commodity service life, due to natural aging, when the strength of the commodity drops to 50%, its ability to ensure safe use is only 1.5 times, and the instantaneous stress that occurs during lifting is now close. This value. Coupled with the inherent functional difference between individual products, this means that the share of broken packages will be increased, and the safety of the products will be greatly reduced. Of course, this is only a theoretical estimation. In reality, due to the differences in the internal materials and the application environment, as well as the functional tolerances between commodities, it is necessary to grasp when the function of a batch of commodities in use has dropped below 50%. Difficulty. However, the container bag with a safety factor of 5 times can be used safely for longer than a product with a safety guarantee of 3 times. The container bag filled with UV-resistant additives has a wider range of applications and is an indisputable reality. Therefore, they There is also a wider world market.

The calculated tension (according to the planning method) of the sling (rope) of the rule 10454-89 of the "Bulk Bag Specification" should be greater than or equal to 6 times the extra load to be allocated to the tension on a single sling (rope) of different types and different rings , And give a safety factor of "6". In practice, this safety factor is different from all lifting experiments. The 6-fold factor of the hoist ring cannot prove that the whole bag has a 6-fold safety factor. It only represents the higher tensile target that the sling needs to reach during independent inspection. . When the sling is connected with the bag body, there are various types of top hanging, side hanging, bottom hanging, etc., and they are connected by stitching. In the side suspension and ceiling suspension, if the base fabric and sutures do not reach a certain level of strength function, the high strength of the sling alone cannot ensure the high performance of the entire experiment; furthermore, the sling and the base cloth are based on different For sewing patterns and sewing methods, the strength loss is also between 10-30%. Therefore, the whole bag lifting experiment needs to hang 3 times the full load and repeat the increase, and the detailed structure of the product is neglected when determining the function of the sling. In the revision of the 2000 version of the "FIBC" specification, in order to ensure the safe loading and unloading of bags, the top-hanging bag and side-hanging bag in the original specification were cancelled. This method seems inappropriate. To ensure quality, we should first rely on proven manufacturing skills and reliable data quality. Top-hanging method bags and side-hanging method bags still have their merits in the processing process and cost, especially in light-duty bag products. Normative guidelines should point out the direction, and should not restrict the useful performance of planners' ingenuity by rules and regulations.

In addition, there are probably clear rules for the "speed" during the overall lifting test of the bulk bag and the "filling" during the falling test of the bulk bag. Experiments have proved that the filling of the sample is massive, granular or powdery, which has an important influence on the experimental results, and the physical density and looseness of the contents also have significant differences in the overall experimental results. We believe that the speed of the experiment should follow the practice hoisting speed of the crane at the port and port, and the function of the filling can be as close as possible to the goods that the customer wants to load. In order to prevent controversy, the specification should describe a kind of "standard filler" dedicated to experiments, as the basis for judging the function of the container bag, and make the technical specifications as good as possible to meet the challenges brought by the market economy.

The "safety factor" is used to ensure the safe use of goods, and it determines the mechanical functions of the various components of the bag body under different construction methods. It reflects the inductive function of the commodity, which is concise and clear. Therefore, it is an important basis in commodity planning. The primary force structure has an important relationship with it. The planning first determines it, and then surrounds the strength assigned to each component. Based on the minimum unit weight that can be guaranteed by the company's drawing ability. Other detailed plans should be arranged in detail around this goal. As for the product, if the "safety factor" experiment can be qualified, it should have an effect on other experiments.

2. For all test methods

In addition to the periodic lifting, there are 5 experiments in the "National Standard" GB10454-2000 clause 5.5 of the "all experimental methods" rule, including the falling experiment, the pressure experiment, the orthographic experiment and the tearing transmission experiment. According to the product experiment of, you can be satisfied with other experiments if you are satisfied with the overall lifting experiment with a safety factor of 5 times.

In the lifting experiment, because the 5 times the load is the force of all parts of the collective, the force per unit area is 5 times that of the extra load. If this experiment can be passed, then the height is separated in the falling test and the dumping test. When it is 0.8M and 3M, with an additional load in its free fall, the sum of its own weight and gravitational acceleration is much smaller than that of 5 times the load. The force allocated to the components of the whole bag is also much smaller than when the load is 5 times the load and from the inside to the outside, which poses no threat to the product.

The meaning of the experiment is to imitate the status of commodity internships. The chord of the world's ocean freighters is more than 0.8M or 0.3M higher than the dock. This kind of experiment has little meaning. If the bag really falls off when the port is hoisted, there are only two options: one is the port operation is wrong, and the other is the product fails the lifting experiment.

can reach a safety factor of 5 times, so two of the 4 rings or one of the 2 rings must also have an extra load of 2.5 times or more of the pulling force. In the upright experiment, the bag is lying on the ground, and the 2 or 1 hoisting ring on the side close to the ground is lifted up with the hook until the bag is lifted off the ground. There is no doubt about the bag. When the bag body is lifted off the ground, due to the skew effect of the single ear lifting, a non-straight component force will occur to damage the structure of the root of the ring. The size of this force component is related to the inclination of the bag body, and is also related to the inner packing plane and the ring. The relative position of the root stitch is related to the unevenness. Usually this tearing force is equivalent to 20-25% of gravity, which will not pose a threat to the sling that has been inspected with a safety factor of 5 times.

In tearing transmission, if the force of more than 5 times the load distributed on a certain part of the carrier 10CM is F, then the force distributed at that place when the extra load is lifted for tearing transmission is 1/5F. The direction of gravity of the contents of the bag is mainly downward, and there is a certain pressure on the sidewall fabric but the contrast is small. The size of this pressure is related to the uneven surface of the content material, the size of the bag body cut surface, and the powdery, granular, and Lumpiness is related to density. At the same time, this pressure is affected by the longitudinal and longitudinal directions of the warp and weft yarns, and the separation of the end of the knife edge at 45 degrees from the straight central axis of the bag body will generate two component forces to transmit to the flat yarn in the warp and weft direction of the bag body. After comparing the messy calculations, we can get the size of these two components. The tearing transmission is part of the overall force analysis of the bulk bag. The comments are compared to “messy”, but the practice proves that the knife edge will not extend.

To sum up, there are many items of all experimental methods in the "International Standard for FIBCs", which include each other in function, and the inspection is messy, and they are all important veto items in the inspection based on the standard. There are many experiments in the whole bag, the experiment period is long, and the experiment cost is also high. This is no longer suitable for the fast-paced and low-cost era characteristics of today's society. In the contract environment, it has the function of concise, clear, and quick to determine the quality of goods, which is the direction of the standard development at that time.

3. The usual rules for the strength of the base fabric, the function of the flat yarn, and the aging of the woven fabric

First of all, in order to satisfy the safety factor, the base fabric should have a higher strength, but not the higher the base fabric, the better. Subject to a specific base fabric component, under the usual rule that tension and elongation are inversely proportional. The flat yarn used for weaving should maintain a good elongation while seeking absolute tension. Without a good elongation, if the tension is over-heated, it will pull out the seedlings and promote, and the aging function of the product will be greatly reduced. When no additives are added, elongation is one of the primary goals for judging the function of the fabric. Once the strength of the base fabric is determined by planning, in the predetermined width, the sum of the tensile force of each monofilament cannot be equal to the measured strength of the base fabric, and there will be 5%-15% weaving loss. This is related to the difference in equipment structure, the degree of newness and oldness, and the material melt index (softness and hardness of the material), the ratio, and the technical method of the flat yarn. The other weft directions have relatively greater strength loss than the warp directions.

Secondly, it is necessary to resolutely eradicate the increase of recycled materials in the production of bulk bags, because this involves safety issues. As we know, although polypropylene material has better mechanical properties, its ability to resist natural aging itself is very poor. If you want to insist on using the function for a relatively long time, scientifically and reasonably participating in the additives is an inevitable choice. If recycled materials are used, one is that the ingredients are difficult to control and the functions of the product are difficult to grasp. The second is that the molecular chain is plasticized twice or even repeatedly, even if the "anti-aging agent" is added, it is uncontrollable.

Third, anti-natural aging is an unpopular subject involving multiple theories and complicated mechanisms. I don’t have a deep entry, but I know a little bit about the anti-aging of plastic woven products. In the seventh issue of "China Plastics" in 1998, there was an article "A Preliminary Study on Polypropylene Fabric Anti-Natural Aging", which commented on the mechanism and effect. doubt. The main idea is: 1. Adding anti-aging agent to the fabric and not adding anti-aging agent, the application effect is significantly different; 2. There are several domestic famous brands of materials that are better than usual materials without adding additives. The function should be relatively strong; 3. The method of adding additives in the quality guess is very important, not only to mix evenly, but also to ensure that it can enter the barrel; 4. The proportion of additives should be appropriate, and the effect of less is not significant, and more It is spoiled; 5. Stabilizer grades should be appropriate. The wavelength to be prevented by the additive should be the sensitive wavelength of all materials; 6. Determine the appropriate stretch ratio, and adhere to the satisfactory elongation under the condition of satisfactory strength requirements, and make it tend to be common; 7. Relative product fabric When it is thicker, the loss of function is relatively small; 8. The anti-aging resistance of the laminated material is better than that of the non-laminated material, and the PE film is better than the PP film; 9. The flat surface of the product is better than the product with wrinkles; 10. Elongation The rate (appropriately) is better than the elongation rate is small; 11. The strength of fibrillated flat yarn is lower than that of non-fibrillated; 12. The anti-aging function of the product should be determined based on the regional climate characteristics.

Fourth, the determination of the inspection results

In the national standard, the judging clauses on whether the bulk bag is qualified or not are 4.2.1, physical function of the base fabric; 4.3, construction skills requirements; 4.4, sewing skills requirements; 5.3.5, all experimental methods, etc., we think these veto items are determined Some of the clauses require simplification and mergers. Scientific planning comes from application internships. The scientific experimental method should be based on the practical application status of the commodity, and the scientific physical and chemical function inspection should be strictly based on the results obtained in the laboratory. The relatively messy inspection methods in scientific experiments should be carried out outside of the norms as much as possible. When implemented in commercial activities and highly operational norms, they should be concise, and the contents of the inspection results that can be repeated with each other. The final inspection should be used as the basis for the determination.

The "Code" itself serves as a standard for inspection. The basis for determination under contract conditions should not restrict the producer's fantasy space and planning creativity. Together, it probably has a strong and significant logic.

For example, some individual companies are restricted by equipment conditions, and the strength of the base fabric of the FIBC is lower. Planning methods such as strengthening the belt can be used to compensate for the lack, and then all the items in the whole bag experiment are satisfied, and the application is not affected. But if the two terms of base fabric strength and all experiments are the basis for determination in GB10454, if the supply and demand sides have a dispute about this, which party should the standard be used as the basis?

The tensile strength of the sling sling should be greater than or equal to 6 times the additional load. The tensile force assigned to each single sling according to the method of the sling should also take into account the loss of strength after sewing, and this loss is also numerical under various technical conditions. Not all in common. It is appropriate to give a reference value or formula for intensity loss as a specification.

The sewing strength of the main body and bottom of the bag should be included in the determination of the overall lifting experiment. The lack of sewing strength of the bag body can be compensated by planning methods such as the bottom hanging type. The commonality of sampling in the sewing part is inherently difficult to grasp, and because the circular and arc-shaped stitches are not evenly stressed, the sampling must increase the probability of inaccuracy in the experiment.

As part of the function of the product can be adjusted by changing the planning method and product structure, the part function of the product should only be given the standard value for reference, and it is recommended that the producer refer to and adopt the method to adjust its own product. The entire experiment is representative of the user, imitating the application status, and if it is unqualified, it will become a veto item and become a guidance basis for adjusting the bag body parts and materials. The determination clause in the current FIBC specification uses part of the condition that can be changed with constant elements to reflect the original value of the determination of the overall condition of the product, which is worth discussing.

5. For appearance inspection and safe storage and transportation

The rules for the appearance inspection of FIBCs are probably further clarified, the inspection criteria are drawn up, and the inspection items are listed based on the inspection characteristics of various methods. For example, square-shaped bags, round-shaped bags, cut-out bags, and bottom-hanging structural bags, etc., some of their dimensions, which important parts should be inspected, and the error of some dimensions, may be regulated. Although these inspections are very important, But it should not be a veto item.

The vague sentences and words in the sentence narration of the "Guidelines" should be clear. For example, "sewing needs are straight", "no significant lack of warp or weft", "no significant defects" and "no abnormalities", and questions about the description of straight, significant, and abnormal words in the meantime, It should be restrained to a certain extent, and then prevent the gums that can be used.

It is accurate that the weight of the FIBC is not restricted in the specification, which can encourage the creativity of the company, show the company's respective expertise and talents, and participate in the competition with lower costs and excellent planning. However, the component error of the FIBC is probably restricted. Although the FIBC has more component data, the difference in function can be compensated by the structure. But after all, weight is not only an important factor in determining the price of a commodity, but also affects the function of the commodity and the competitiveness of the market.

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Time of issue:2022-08-06 11:27:16

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