Regarding the selection of safety factors
Thread Content
In the new revisions to the \"Safety Technical Inspection Regulations for Fixed Pressure Vessels,\" adjustments were made to the safety factors. For conventional design of steel materials, the safety factor for tensile strength was reduced from 3.0 to 2.7, while the safety factor for yield strength was reduced from 1.6 to 1.5. For analytical design of steel materials, the safety factor for tensile strength was adjusted from 2.6 to 2.4, with the safety factor for yield strength remaining unchanged at 1.5. So what determines the selection of the safety factor? As the author understands it at present, the selection of the safety factor depends on the method used for stress calculation and its accuracy, as well as on the severity of structural failure. It also depends on the properties of the materials and the nature of the loads; for chemical containers, the corrosive effects of the medium must also be taken into account. Of course, the selection of the safety factor is a matter that requires great caution, as it represents the level of design sophistication of a pressure vessel and serves as a comprehensive impact factor. The safety factor is a comprehensive factor that takes into account materials, design, manufacturing, non-destructive testing, pressure testing, operation, and regular inspections. It can be said that the safety factor is present throughout the entire life cycle of a vessel, serving as the foundation for its design. For designers, it is far from sufficient to merely know the value of the safety factor; it is also important to understand why that value exists. Of course, these are just my personal opinions – I encourage everyone to share their own views on the safety factor.
Hehe, you’re interpreting it in too complex a way. In fact, it’s simply put: the higher the safety factor, the more conservative it is.
Although a higher safety factor is better, it can lead to waste of social resources; it’s sufficient to meet the needs
The selection of the safety factor for pressure vessels should comply with **standard regulations**, as these standards are established through extensive research and analysis. However, over time, the properties of the materials used have changed; therefore, the safety factor for pressure vessels can be determined based on the actual operating conditions. Yet, it is necessary to have sufficient data, experimental support, and a solid understanding of safety aspects to make such decisions.
From the original text posted by the author, it seems that what is being referred to is the coefficient used to determine the allowable stress; however, based on your subsequent explanation, there seems to be a misinterpretation involved. In general, the selection of the safety factor reflects the level of material manufacturing and the quality of experimental simulations. It is also determined by taking into account the accuracy of the analysis and calculation methods for stress conditions, as well as the uncertainty of external loads. Factors such as corrosion mentioned by the author have no relation to this coefficient. This is just my personal opinion; feel free to correct me if I’m wrong!
The claim about the fifth floor seems to be more accurate; it is also related to **energy policies and trade barriers. For example, the level of material manufacturing, testing capabilities, and design methods in the United States are all higher than those in China; the basic data related to materials is also more systematic and scientific there. However, the safety factors used in the United States are higher than ours, while those in Europe are relatively lower.
The safety factor should be a **comprehensive reflection of design techniques and methods, as well as the quality of material production and equipment manufacturing. Although reducing the safety factor can enhance the competitiveness of manufacturing enterprises in the international market, various factors such as material production, equipment manufacturing, and design technology also need to be improved. In recent years, the production level of pressure vessel materials in our country has improved significantly; specialized standards for such materials have been established, with requirements in some areas being even stricter than those for corresponding materials abroad. There have also been significant improvements in design techniques and methods; computer technology has been widely applied, design standards have been established for various types of equipment, and structural design takes increasingly comprehensive and rational account of various loads. However, the manufacturing standards for pressure vessels are not satisfactory. Due to the development of the market economy, various sectors and enterprises are focused on improving efficiency, paying insufficient attention to quality; some older enterprises have even seen a decline in quality. Quality supervision agencies also fail to provide adequate oversight of these enterprises. In some places, it is possible to obtain a manufacturing license by paying a small fee, and some enterprises even operate without such licenses. In the Jiangsu and Zhejiang regions alone, there are three to four thousand enterprises with and without licenses. Therefore, considering the current level of manufacturing, reducing the safety standards in this way seems somewhat hasty.
“It cannot be entirely agreed that the safety factor is a reflection of the **design quality of pressure vessels**; rather, it reflects more the **manufacturing and testing standards of such vessels**.