| 摘要 |
PURPOSE:To enable the shortening of a blanking time as much as possible by detecting a pipe end by a flaw detection signal itself to eliminate effect of disturbing factors of conveying speed or the like. CONSTITUTION:In a conveying path for a steel pipe 1 being carried by a conveying roll 2, a photo sensor 3 to detect the passage of the front and rear ends of the steel pipe 1 and a through coil 4 to detect flaws are disposed in this order from the upstream side. Component coils 4a and 4b of a coil 4 are connected so as to be opposite arms of a bridge circuit 7 respectively and the coils 4a and 4b are energized by a high frequency current outputted from an oscillator 19. Under such a condition, the tip of the steel pipe 1 is detected and in addition, when a signal generated from a flaw detector meets specified requirement, this signals used as detection signal for the tip to start the detection of flaws in the steel pipe 1. The rear end is detected and in addition, when the signal emitted from the flaw detector meet specified requirements, this signal is used as detection signal for the rear end to end the detection of flaws in the steel pipe 1. |
