Valve insertion method and cutting tool

Abstract

A valve insertion method without stopping passage of fluid, wherein, first, a part of an already-installed pipe is enclosed air-tightly with a valve casing, a milling type cutting tool which has cutting edges on a free end surface and an outer circumferential surface thereof, and a gate being housed in the valve casing with the gate and the cutting tool fixed thereto. The gate and cutting tool are provided in positions spaced from each other in the axial direction of the already-installed pipe. A worker then feeds the cutting tool in the radial direction of the already-installed pipe as he has the cutting tool make cutting motions for cutting the pipe by the rotation of the cutting tool. The valve casing is then turned in the circumferential direction of the already-installed pipe as the cutting motions are kept made, whereby a cut groove cut in the direction of the range of the whole circumference of the pipe is formed. After the grooving operation is finished, the worker takes out the cutting tool from the valve casing, and then closes an operation valve. After the grooving operation is finished, the worker transfers the valve casing in the axial direction of the already-installed pipe, whereby the gate is transferred to a position which corresponds to that of the cut groove.