(1) before open the slot should drill a stopper hole at both ends of the cracks, diameter 8-12mm. It should be deeper than the depth of the crack.

(2) foot diameter tank should be as small as possible, but the cross-sectional shape and the groove wall angle and bottom rounded corners should meet the welding requirements.

(3) For the original crack repair welding area, close to the base metal, when openning the slot should be appropriate to extend the base metal area.

(4) When using an electric arc to dig and shovel the slot, carburized layer and hardened layer must be rubbed off with a grinding whell and polish.