PLUG FLAW AND WEAR DETECTOR FOR ROLLING MILL FOR MANUFACTURING SEAMLESS STEEL PIPE

PURPOSE:To enable a flaw or wear to be detected reliably and accurately, by irradiating a traveling plug by a flash light of a strobe means, picking up a stationary image of the plug by an ITV camera, and processing this image by a CPU. CONSTITUTION:When a plug 6 attached to the distal end of a mandrel bar 5 enters the field of view of an ITV camera 11, a flash light 12 emits light and, in synchronism with this, the stationary image of the plug 6 is stored in a memory 16' when the plug 6 has not yet been used, and in a memory 16 when it is in use. The two images are subjected to a profiled extracting processing in an image processing circuit 19, and an amount of offset between the images is then obtained. An object image is moved so as to coincide with a reference image, thereby correcting the offset, and a difference therebetween is then obtained. This difference is processed, e.g., binary-coded, and areal calculation is carried out to obtain quantitatively the size of a flaw or wear. When the obtained value exceeds a preset value, an alarm is sounded. Accordingly, the detecting operation can be automatically conducted, and detection can be carried out reliably and accurately on the basis of a predetermined reference value.