Heat treatment area after patching of internal-pressure vertical vessels
Thread Content
After a circular hole is patched in a vertical container, heat treatment is carried out according to the requirements of the original design. How should the area for local heat treatment be determined? Just this patched area?
Welds and heat-affected zones in the repaired area.
This depends on the location of the patch; if it is on the cylinder body, local heat treatment should be applied to the entire circumferential area of the cylinder body, including the patch area. If it is on the head, considering local heat treatment of a circular area within the patching region is an option.
On each side of the circumferential seam, it shall be not less than 2 times the plate thickness; for joints, accessories, and repair welds, it shall be not less than 6 times the shell plate thickness. It shall form a continuous circumferential heating zone, with the temperature gradient at the edges being not less than 1/2 of the insulation temperature