A double-wall spiral welded pipe includes a first steel belt layer and a second steel belt layer which have equal widths, are arranged in parallel and align with each other; at least two supporting steel bars perpendicular to the first steel belt layer and the second steel belt layer are arranged between the first steel belt layer and the second steel belt layer; the supporting steel bars are arranged on end parts of two sides of the first steel belt layer and the second steel belt layer and extend together with the first steel belt layer and the second steel belt layer; and the first steel belt layer, the second steel belt layer and the supporting steel bars on the end parts of the two sides are mutually welded to form a double-layer composite steel belt with a rectangular section in an extending direction.

An apparatus for automation of weld seams machining of a wind turbine tower is provided. The apparatus includes an automated arm; a machining tool fixed to the automated arm; a compensator system fixed to the machining tool or being part of the automated arm; a joint visor that identifies and locates the weld seam; and a control unit to coordinate the movement of the machining tool with the compensator system and the joint visor. A method of performing a welded circular seam machining in a wind turbine tower with the apparatus is also provided.