PURPOSE: To detect a plugless rolling condition in a piercer by fetching the image of the shell of a pipe stock delivered from a piercer into a sensor and computing a measuring value corresponding to the outer diameter of pipe stock for comparing the computed value with a set value.
CONSTITUTION: The image of the shell 3b of a pipe stock 3 delivered from the piercing rolls 2, 2 of a piercer 1 is fetched into an image sensor 7a through the lens 7b of a linear ray camera 7. The image is converted into an electric signal, which is outputted, as a timing signal, in sequence at every fixed time. A controller 8 compares the number (n1) of voltage-pulse (measured value) outputted from the sensor 7a with the number (n0) of previously set pulses (set value), to output an alarm signal to an alarm 9 when n1<n0. The alarm 9 is actuated by the signal to output an alarm through light or sounds, etc. Accordingly, the piercer 1 is stopped at once when a plugless rolling condition is informed.
YOSHIDA MASATO
HATANAKA MASAYUKI
KAWABATA SHIGEO
