1, SGB test block This standard adopts SGB test block and SRB test block, SGB test block is used to determine the flaw detector, press the probe system performance and do high speed and calibration of food. Six different SGB test blocks were made according to the different curvature of the inspected pipe fittings. 2. SRB test block The material of SRB test block is cut parallel to the axis on the inspected part. The test block is used to compare the depth of the underpenetrated test block at the root of the weld. Figure 8-2 shows its shape and dimensions. 3, longitudinal defect test block 4, horizontal defect test block