【Haichuan Chemical Accident Update】Fly ash silo collapses in Wuwei, Gansu

According to industry experts, accidents such as the collapse of steel plate silos have their objective causes, but there are also certain human factors involved. These are summarized as follows: For fly ash silos, 1) the design strength is almost always severely insufficient. After inspections by professional technicians of the collapsed steel plate silos, it was found that in most of these cases the design strength was greatly inadequate; many of these silos had serious deficiencies in both their circumferential tensile strength and vertical compressive strength, with particularly large differences in terms of stability. 2. Unreasonable structure of the storage tank and improper selection of load parameters: Different steel plate silos experience significant variations in the forces exerted on their walls due to the different materials stored within them; similarly, the loads on the tank roof also vary greatly. Design must be carried out based on the characteristics of the materials stored. When designing each steel silo, it is necessary to take into account not only the properties of the materials but also the characteristics of the industry; otherwise, collapse accidents are likely to occur. The storage silos made of steel plates in the building materials, grain, and petroleum industries should not have their intended use altered without conducting relevant calculations. 3. Impact of low-temperature environments: Low temperatures are an important factor that contributes to the collapse of steel silos, but it can be said with certainty that they are not the decisive factor; otherwise, any type of steel silo or steel structure in most cold regions of our country would be unable to function properly and would have already been damaged by freezing. In the collapsed steel silos, technicians observed on-site that the fracture surfaces of a few damaged steel plates showed signs of brittle failure; the steel plates had been \"damaged by freezing.\" However, in most cases, the collapse was caused by structural limitations in the design, which led to localized damage in the steel silos and subsequent collapse. For silos made of steel plates that are used in low-temperature environments, the structural design must take into full account the effects of expansion and contraction on the structure. With a proper structural design and sufficient strength, the destructive impact of low-temperature conditions on the structure can be eliminated, allowing the structure to be used safely. Of course, if low-temperature steel plates are chosen for use in such environments, the safety of the silo is further ensured. 4. Improper material selection: Some of the collapsed steel silos were constructed using Q235B steel plates. It is possible to use ordinary steel plates for such silos as long as the strength requirements are met; however, using low-temperature steel plates ensures that the silos can avoid the problem of cold brittleness during use, thereby reducing the likelihood of structural failure. Therefore, during construction and reinforcement, it is recommended to use low-temperature steel plates; in particular, Q345 series low-temperature steel plates are the preferred choice, as they are safe and also help to reduce costs significantly. 5. Construction quality defects: In recent years, due to the accelerated pace of construction of steel silos, there have been many instances of inadequate construction management. Additionally, some users failed to make proper preparations in advance and wanted the structures to be put into use as quickly as possible, which prevented the contractors from carrying out the work at a proper pace and made it difficult to ensure quality ； On the other hand, due to the varying technical levels of the construction firms, project owners choose those offering lower prices in order to save on costs, which further leads to a decline in project quality. As a result, several steel silos are built at the same time, with those completed faster being emptied first, while those of slightly better quality being emptied later. In such cases, no matter how well the initial design and material selection are done, if the quality control during construction is inadequate, it is not surprising that accidents occur with steel silos. 6. Improper use: Some users, during the operation of steel silos, arbitrarily increase the loads on these structures after they have been built. This includes adding equipment on the silo roof, constructing walkways or imposing loads on those walkways, increasing the loading capacity during storage (often due to excess volume and insufficient strength in the design), adding loads to the sides of the silo, and making arbitrary openings in the silo structure. Such practices increase the risk of accidents, and therefore require high levels of vigilance. In summary, while there may be certain natural environmental factors contributing to the collapse of steel silos, the root cause lies in human factors – specifically, the substandard quality of construction work. To prevent such incidents from occurring, it is essential to choose reputable, professional manufacturers with strong capabilities and advanced technical skills for constructing steel silos.