Structural integrity of pressure vessels is of great importance in ensuring their safe exploitation. Due to this, a number of standards are developed in order to define the criteria according to which materials, technologies and test methods are selected for pressure vessels, particularly when it comes to welded joints. Because of the nature of the welding process, welded joints will typically contain different types of defects, some of which could greatly endanger their integrity. Cracks in particular are the cause of pressure vessel failure.
The goal of this paper is to present the standard SIST EN ISO 5817:2014 and emphasize the changes and additions that are made, compared to the previous version, SIST EN 5817:2007. The standard includes recommendations and requirements related to the presence of multiple types of defects in welded joints subjected to fatigue loading. Since fatigue crack growth greatly contributes to failure of pressure vessels, for the first time this standard covers a very important topic. Some of the earlier work related to multiple defects in welded joint is also shown in the paper, and used as examples.
Keywords: fatigue cracks, welding defects, SIST EN ISO 5817:2014, structural integrity