Three aspects ascertainment of interior defects in welded joints of pressure vessels — an application of the technique of 3–dimensional radiographic detecting

Since welded seams of pressure vessels are generally rather narrow, for the longitudinal weld the general formulas based on the technique of stereoscopic radiography can be directiy applied for determining the location of the point defect. But for circular weld, owing to that films during photo-taking are curved ones whereas they are to be made flate during observation and measurement on a 3–dimensional detector, so some further equations must be established to satisfy the relations between the stereographic curevd films and the assumed flate films and thereby to determine the spatial point location for the defects in pressure vessels. With these epuations and by surveying of the point image of defects, coordinates ZA, XA and YA can be determined and hence the real position of defects in vessels. Ascertainment of point location of defects is the background for the dimensional location and quantitative analysis of defects. Once ascertained, such geometric parameters as depth of defects, height of defects themselves, their orientation, size and spacing can all be determined consequently.