1引言简体环缝进行射线探伤由于受到曲率的影响，需要保证X射线垂直透照被检区域并使透照、贴片的内外中心重合。目前简体环缝确定透照部位内外中心的方法是：首先在环缝的外侧或内侧选定位始点（如T接缝为始点）；标出需透照部位的中心；然后测量出透照中心至定位始点的弧长， 1 Introduction Simplified girth radiography Due to the influence of the curvature, it is necessary to ensure that the X-ray vertical transillumination of the examined area and make the transillumination, the inner and outer center of the patch coincide. At present, the method of determining the inner and outer centers of the transillumination site is as follows: Firstly, select the start point outside or inside the annular gap (such as the beginning of the T-joint); mark the center of the site to be transilluminated; then measure the transillumination center Positioning the starting point of the arc length,