PURPOSE: To ease the residual stress of joint parts and improve grain bounary type stress corrosion cracking resistance by applying even presure through an elastic material over the range of a fixed length to the inside surface of pipes with the welded joint part coupling the pipes in the axial direction as a center.
CONSTITUTION: The relieving device consisting of a pipe expanding medium 15 being elastic material, pressing rod 16, backup ring 17, sleeve 18 and hydraulic cylinder 19 is inserted into pipings 5, 6, after which the piston of the cylinder 19 is operated, by which force F is given to the pressing rod 16 to move it axially. As a result of this, the force is exerted to the pressing rod head 16a and the pipe expanding medium 15 is compressed in its axial direction. By the expansion in the radial direction along with this, the pipings 5, 6 and butt weld zone 7 are force expanded evenly in the radial direction, whereby plastic deformation is given and the residual stress to the weld zone is relieved.
KANBARA HIDEAKI
MURAKAMI YUKIMASA
MATSUMOTO TERUO
TAMAI YASUKATA
