Abstract
An ultra compact orbital welding equipment for butt welding of water-wall tubes of power generating boilers at erection sites has been developed. The minimum radial clearance of the welding head is 17mm, and this value is minimum in the world. To achieve the 17mm radial clearance, the new arc length control mechanism and the flat welding torch of 7mm thickness have been developed. The differential motion mechanism was used for the arc length control, and the driving gears were set up in the part fixed to the tube. To make the flow of the shielding gas a laminar flow, the filter was set up at the gas blow exit of the thin torch. Using the developed orbital welding equipments, several thousand joints of water-wall tubes of power generating boiler have been successfully welded at erection site.
