Rubber cap device suitable for magnetic flux leakage inner detection for pipeline

The utility model discloses a rubber cap device suitable for magnetic flux leakage inner detection for a pipeline. The rubber cap device comprises a rubber cap equipped with a cap bottom, a cap wall and a cap edge. A first stage anti-blocking groove is arranged in the inside surface of the cap wall close to the cap edge and is arranged along the peripheral direction of cap edge in the inside surface of the cap wall. The groove depth of the first stage anti-blocking groove is half or two thirds of the thickness of the cap wall. The rubber cap device suitable for the magnetic flux leakage inner detection for the pipeline has following beneficial effects: the rubber cap device is capable of automatically eliminating resistance and driving a detector to continuously operate during process of thickness changes of a joint, a pipeline wall and a valve and avoiding shutdown and burst of the pipeline.