| 摘要 |
<p>The workpiece moves longitudinally through sets of probes which travel periodically in a transverse direction, and differential signal voltages are created by the probes. The probes consist of two longitudinal rows, each contg. eight sensors aligned in the same direction as the welded seam; and the sensors in each row are connected in pairs to obtain the differential voltages. One pref. method of connection is to join alternate probes, i.e. in a row a-h, the connections are ac, bd, ce, etc. The pref. inspection appts. uses a rotating head contg. the two rows of probes which feed signals to an electronic circuits. Used for the inspection of seam welded pipe using the tray magnetic flux method. The invention reduces the disturbance due to the seam to 1/2-1/20th of that in known appts. so defects of 5% of the wall thickness are detected with certainty.</p> |
