Device and method for measuring centrality deviation of butt-joint pipelines with different pipe diameters

The invention discloses a centrality deviation measuring device and method for butt joint pipelines with different pipe diameters. The centrality deviation measuring device comprises a first storage disc (11), a second storage disc (12), a rotating disc (2), a light beam emitter (51), a reading dial (52) and a folding telescopic rod assembly. A rotating disc is rotatably and concentrically embedded in a first storage disc (11) and a second storage disc (12), a light beam emitter and a reading dial are concentrically embedded in the rotating disc, a plurality of sets of folding telescopic rod assemblies are circumferentially connected to the first storage disc and the second storage disc, and the folding telescopic rod assemblies synchronously stretch out and draw back in the radial direction of the first storage disc and the second storage disc. The first storage disc and the second storage disc are concentrically arranged in the pipeline (6) through the folding telescopic rod assembly, and the light beam emi