The present invention is generally related to welding torches and more particularly to flexible welding torches.
In nuclear steam generators, the tubes are expanded at the level of their tube sheets to form a tube to tube sheet weld. After the steam generator has been in service for a certain period of time, the steam generator and tubes must be examined for the presence of defects that may have occurred during use. The detection of defects in a tube may require the tube, or a portion of the tube, to be removed to allow for closer inspection of the tube defects and/or for replacement of the tube. By relaxing the tube expansion, removing the tube to tube sheet weld, and cutting the tube to the sample length desired, the tube sample can be removed using a hydraulic jacking sequence. The preservation of any tube defects is vital during the removal of the tube sample. Therefore, it is advantageous to reduce the amount of pull force necessary to remove the tube sample. The most common way of accomplishing this is by making various passes such as vertical, spiral, and zig-zag passes on the inner diameter of the tube with a torch. The melting of the tube inner diameter and subsequent solidification causes the tube to contract and pull away from the tube sheet. A tungsten insert gas (TIG) torch is the most suitable type of torch for insertion into a tube and for producing the necessary heat. TIG torches presently known in the industry require 24 to 42 inches of vertical clearance. This presents a problem when tube samples must be removed from the periphery of the tube sheet since the curvature of the steam generator head provides a limited vertical space. Also, some known TIG torch assemblies require the entry of personnel into the steam generator to position the weldhead on the tube sheet. This is undesirable due to the increased radiation exposure.
Accordingly, there exists a need for a TIG torch assembly that requires little vertical clearance and that can be remotely positioned along the tube sheet after it has been placed inside the steam generator.
USPTO Backgrounds
USPTO Backgrounds