Directing against problems of frequent leakages occurred in operation and the repair quality of header handholes being difficult to ensure on the boier of a 25 MW unit in Huating Power Plant

the header handholes have been retrofitted

removing the caps of original handholes of the header

and welding d133mm×13mm short tube of 20G type on end face of the header

and spherical sealing heads being used. Meanwhile

in order to resolve the problem of stress corrosion rupture between the blank pipe and the end cover resulting from accumulated water

the blank pipe has been shifted upward

making the inner wall to be aligned with the lower side edge of handholes

Vshaped bevel welding is used between the sealing head and the blank pipe. After retrofitling

the effectiveness is excellent

having thoroughly solved the leakage problem of handholes.