Abstract: Provided is a method for manufacturing a cylindrical member which includes end bending of respective end portions of a plate material in a longitudinal direction, primary grooving of respective end surfaces of the plate material subjected to end bending, bending of the plate material to a ring shape, secondary grooving of respective end surfaces of the plate material subjected to bending in a ring shape, and joining of respective end surfaces of the plate material. Therefore, it is possible to manufacture a high-quality cylindrical member.

Abstract: A welding system of cylindrical structures which welds a welding end surface of an upper cylindrical structure and that of a lower one in an axial direction thereof, includes: two or more welding apparatuses opposite to the welding end surfaces and disposed at equal arrangement intervals in the circumferential direction thereof; a moving device configured to rotate the upper and lower cylindrical structures relative to the welding apparatuses in a circumferential direction thereof; and a control device configured to control the welding apparatuses and the moving device. The welding apparatus has a filler metal and a heating source therefor, and melts and fuses the filler metal on the welding end surfaces to weld them, and the control device is configured to continuously rotate the upper and lower cylindrical structures an angle of the arrangement interval by the moving device, while welding the welding end surfaces with the welding apparatuses.

Abstract: Provided is a method for manufacturing a cylindrical member which includes end bending of respective end portions of a plate material in a longitudinal direction, primary grooving of respective end surfaces of the plate material subjected to end bending, bending of the plate material to a ring shape, secondary grooving of respective end surfaces of the plate material subjected to bending in a ring shape, and joining of respective end surfaces of the plate material. Therefore, it is possible to manufacture a high-quality cylindrical member.

Abstract: A distortion correction method includes: a reference surface forming process for fabricating a reference surface as a circumferential surface in an outer circumference of a raw pipe having both axial ends to which fitting members are welded; a connecting member installation process for installing a reference surface of the raw pipe in a roller contact member that rotatably supports the raw pipe; a measurement process for measuring a tilt of the fitting member rotating along with the raw pipe by virtue of the roller contact member with respect to an axial direction of the raw pipe; and a distortion correction process for performing TIG welding for a weld portion between the raw pipe and the fitting member on the basis of a result of the measurement in the measurement process to correct the tilt of the fitting member with respect to the axial direction of the raw pipe.