Breathing port structure of zero-emission normal-pressure tank

The utility model relates to the technical field of normal-pressure tanks used in oil production, storage and transportation processes. The utility model relates to a breathing port structure, in particular to a zero-emission normal-pressure tank breathing port structure. The device comprises a breathing port main pipe and a breathing bag, a fixed flange and a clamping flange are respectively arranged on the breathing port main pipe; a tank flange is arranged at a tank opening of a normal-pressure tank, a contraction opening of a breathing bag is formed between a fixed flange and a clamping flange, the contraction opening is connected to a breathing opening main pipe through the fixed flange and the clamping flange, the fixed flange and the clamping flange are connected with the tank flange, and the breathing opening main pipe is connected to the breathing opening of the normal-pressure tank; an inflation valve and an emptying valve are further arranged on the breathing opening main pipe. The connecting and s