Generally, the cylinder where the manhole of a typical oil tank connects with the tank wall penetrates through the tank wall. This type of manhole is not conducive to the lifting and sealing of the floating roof. A core-equipped manhole features an additional core plate inside the manhole cover that matches the curvature of the tank wall and is flush with it. For ease of opening and closing, a rotating arm and lifting lug are installed on the connecting cylinder at the orifice, allowing the manhole cover to remain attached to the oil tank during operation. It is installed approximately 2400 mm from the bottom plate of the oil tank for maintenance personnel to inspect the floating roof.