Why does the uneven welding surface of the cfb boiler water wall cause wear?

　　(1) The fins at the variable diameter of the water wall are not evenly butted up.

　　(2) The on-site installation hoisting hole was not polished and smooth when repairing the fins.

　　(3) After the lower fins were separated during the installation of the water wall screen, the welding process wasn't done well enough.

　　(4) The welded junction of the water wall is not polished and smooth, resulting in erosion and wear.