OUTER CIRCUMFERENTIAL LENGTH MEASURING METHOD OF SPIRAL STEEL PIPE AND ITS DEVICE, AND MANUFACTURING METHOD OF SPIRAL STEEL PIPE AND ITS EQUIPMENT

摘要

PROBLEM TO BE SOLVED: To provide an outer circumferential length measuring method of a spiral steel pipe and its device capable of measuring the outer circumferential length of the spiral steel pipe just after welding the outer surface, and a manufacturing method of the spiral steel pipe and its equipment capable of correcting successively a molding condition of a strip corresponding to fluctuation of the outer circumferential length of the spiral steel pipe. SOLUTION: A transmitter 19 and a receiver 20 of a surface wave are arranged on the outer surface of the spiral steel pipe 18, and a propagation route of the surface wave is set on a section substantially vertical to the steel pipe axis of the spiral steel pipe 18 across a weld bead part 23 of the spiral steel pipe 18, A propagation time of the surface wave from the transmitter 19 to the receiver 20 is determined, and the route length of the propagation route is calculated by using the propagation speed of the surface wave, and the outer circumferential length of the spiral steel pipe 18 is calculated from the distance between the transmitter 19 and the receiver 20 and the route length. COPYRIGHT: (C)2006,JPO&NCIPI