What are the limits for minor dents in aluminum alloy tubes?

In the context of aluminum alloy tubes, the acceptance criteria for minor dents are generally defined to ensure the structural integrity and performance of the tubing. Minor dents can affect the flow characteristics and mechanical properties of the material. The limits you mentioned—10% of the wall thickness and 20% of the original diameter—are established safety standards in the guidelines for maintenance and inspection of aluminum alloy tubes.

When looking at these criteria together, both measurements serve as a way to quantify the severity of the dent. The 10% wall thickness limit relates to how much material strength could be compromised locally due to the dent, while the 20% diameter limit considers the overall structural integrity and potential for kinking or failure in conditions of stress.

This dual standard allows for a comprehensive assessment, ensuring that any dent that falls within either of these limits can be classified as minor and therefore does not necessitate immediate replacement. Consequently, recognizing that a dent can be evaluated based on either of these metrics explains why both thresholds are included in the correct answer.