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What is ISO 5817:2016?

ISO 5817:2016 is an international standard that defines the levels of imperfections in welded joints. It provides a classification system to evaluate the quality of welds and sets the criteria for their acceptance or rejection.

Importance of ISO 5817:2016

ISO 5817:2016 is crucial in industries where welding plays a significant role, such as construction, manufacturing, and automotive sectors. It ensures uniformity in welding quality assessment worldwide, promoting safety, reliability, and efficiency in welded products.

Classification Levels

ISO 5817:2016 establishes three quality classes based on the size and number of imperfections in a welded joint: Level A, Level B, and Level C.

Level A:

This is the highest level of quality standard, applicable for critical structures where safety is paramount. Welded joints in this class must have zero unacceptable imperfections.

Level B:

Joints in this class are allowed to have minor imperfections that do not impact functionality or strength significantly. It is suitable for general applications where safety is still important, but not at the same critical level as Level A.

Level C:

This class permits a higher degree of imperfections compared to Levels A and B. It is typically used for non-critical applications or environments where the appearance or minor defects do not affect the function of the welded structure.

Acceptance Criteria for Imperfections

ISO 5817:2016 defines various types of imperfections and specifies maximum allowable sizes and quantities for each class. Some common imperfections include cracks, lack of fusion, excessive penetration, and porosity. Welders, inspectors, and manufacturers refer to the standard to determine if a weld meets or exceeds the specified acceptance criteria.


In conclusion, ISO 5817:2016 plays an essential role in ensuring the quality of welded joints worldwide. It provides a standardized classification system that helps professionals assess and categorize the imperfections observed in welded structures. Adhering to this international standard promotes safety, reliability, and consistency in welding practices across various industries.


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