Application of advanced NDT methods to assess structural integrity of pressure vessel welded joints

Abstract

The review of non-destructive testing of pressure vessel for compressed air is given, as well as the assessment and analysis of defects on the integrity of the vessel itself. The focus here is on welded joints, as the most critical areas in pressure vessels, especially if thickness is large, like in the case considered here (50 mm), cylindrical air storage vessels made of HSLA steel. Toward this end conventional NDT methods, such as UT and Radiography are used in the first phase of this research, providing valuable data for structural integrity assessment based on detected unacceptable defects in welded joints. Anyhow, since few unacceptable defects were found by conventional UT, there was a need to use advanced NDT UT methods, such as Phased Array Ultrasonic Testing (PAUT), to evaluate defect position and size more precisely. In this way risk of failure can be assessed more reliable, which is of utmost importance for pressure vessel where probability of failure is low, but the consequence of failure is potentially catastrophic, like in the case considered here.