MONITORING METHOD OF THICKNESS DEVIATION GENERATION OF SEAMLESS PIPE

PURPOSE:To reduce the generation of a defective product by thickness deviation with taking quickly the counter measure for thickness deviation prevention by measuring the displacement quantity with providing a displacement measuring instrument on the outlet side of a inclined roll and by monitoring the thickness deviation generating state based on the measured value thereof. CONSTITUTION:The laser beam generated at the laser beam generating part 61 of a displacement measurer 6 is irradiated on a hollow shell S or mandrel bar 3 through an irradiating lens 62. The reflected beam thereof is projected on the detecting face of the optical detecting element 64 which is provided in parallel in the moving direction of the hollow shell S through an image forming lens 63. The displacement quantity in the shaft core direction of the hollow shell S and mandrel 3 can be taken as the displacement quantity in the shaft length direction and with detecting the signal thereof by a position detecting part 65 the detecting signal is recorded to a recording meter 70.