Three-section marine drilling riser expansion device

The invention discloses a three-section type marine drilling riser telescopic device which comprises an inner barrel assembly, a middle barrel assembly and an outer barrel assembly which are sequentially arranged, the inner barrel assembly and the middle barrel assembly are connected through a locking pin shaft, the middle barrel assembly and the outer barrel assembly are connected through a locking pin shaft, and an annular space is sealed between the inner barrel assembly and the middle barrel assembly through an upper packing assembly. An annular space is sealed between the middle cylinder assembly and the outer cylinder assembly through the lower packing assembly. According to the telescopic device, a three-section structure of the inner cylinder, the middle cylinder, the outer cylinder and the like is adopted, the stroke is the sum of the stroke between the inner cylinder assembly and the middle cylinder assembly and the stroke between the middle cylinder assembly and the outer cylinder assembly, and com