Outer pipeline crawling robot

The invention discloses an outer pipeline crawling robot which comprises three layers of annular bases arranged in sequence in the longitudinal direction, every two adjacent layers of annular bases are connected through a lifting telescopic cylinder arranged in the longitudinal direction, the center of each annular base is provided with a through hole allowing a pipeline to penetrate through in the longitudinal direction, and a plurality of climbing foot assemblies are arranged around the circumference of each through hole in an array mode; each climbing foot assembly comprises a foot rod, a friction foot pad, an elastic piece and a foot lifting telescopic cylinder, the foot rod is transversely pivoted to the annular base and forms a first supporting arm downwards and obliquely extending from the pivoted position to the through hole, the friction foot pad is fixed to the tail end of the first supporting arm, and the elastic piece is arranged between the foot rod and the annular base and drives the foot rod to