Square and Round Curl Analysis of Closed Steel Drums
Ma Jianxiang
In China, there are two main types of 200-liter closed steel drums: square (rectangular) and round. According to the production situation in more than a dozen steel drum manufacturers in Xinjiang, both square and round designs are commonly used together. But how do these two types perform differently? What are their advantages and disadvantages? Based on years of inspection experience, when it comes to three key physical tests—airtightness test, hydrostatic test, and drop test—there isn't much difference between square and round curled drums in terms of leakage resistance during the airtight and hydrostatic tests. However, the drop test reveals a significant difference. Square curled drums have a higher probability of cracking or leaking compared to round ones. Why is this the case? Let's take a closer look at the differences in the crimping process.
When materials undergo deformation, internal stresses are generated. These stresses tend to concentrate in areas where deformation occurs. If the material is deformed beyond its yield point, cracks may form. This is especially important in the design of steel drum edges, as stress distribution plays a critical role in durability.
In the case of a round curl, the stress from material deformation is evenly distributed along the entire edge. This prevents stress concentration at any single point. On the other hand, in a square curl, the stress tends to accumulate at the curled ridge, leading to higher local stress levels.
When a steel drum filled with liquid falls from a certain height, especially at a 45-degree angle, the square curled drum is the first to make contact. The impact force causes deformation, and due to the high internal stress, the force can exceed the material’s allowable limit, potentially causing the metal plate to crack. Even if no crack forms, the combined forces may cause severe deformation of the curl, pulling apart the layers and resulting in leaks. In contrast, a round curled drum distributes the external impact force evenly around its circumference. This reduces the likelihood of exceeding the material's strength limits, minimizes curl deformation, and maintains the compact structure of the rolled edge. As a result, the round curl is less likely to crack or open.
Based on long-term inspections of most steel drum factories in Xinjiang, it has been observed that round curled drums perform better during drop tests. According to national standards, when filled drums are dropped from a height of 1.2 meters, round curled drums show significantly fewer issues compared to square ones. This is why many manufacturers consider round curled drums to have a higher safety margin. From the perspective of real-world loading and unloading processes, once filled with liquid, round curled drums demonstrate better impact resistance and can withstand rough handling, while square curled drums are less adaptable in such conditions.
Of course, from a manufacturing standpoint, producing round curled drums requires higher precision in the chamfering of the rolling wheel. Since the rolling wheel is a wear part, the process can be challenging. Operators may encounter difficulties in maintaining consistency, which is why some production facilities opt for square curls instead of round ones.
Square Curl
Round Curl
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