The leakage of some heat-exchange tubes in high-pressure heater has appeared during repair process in one power plant.The solid Cr18Ni9 steel plug and stainless steel electrode were used in original plugging process

and cracks have occurred in weld-joints of leakage-plugging due to different materials of the electrode and the tube-plate

thereby

having larger difference in expansion coefficient.After improvement of the technology

the hollow plugs of no.20 steel and J422 electrode are used

the materials are similar to that of the tube-plate

and cracks haven't occurred after weld-plugging.The stress analysis using finite element method shows that the residual stress of welding with hollow plugs is lower than that of plugs with solid structure.