The impact of pipeline bend on bi-directional pig and the theories for the optimal pig design

As a kind of pipeline robot, pig is needed to perform operations such as dewatering, cleaning and internal inspecting to improve the efficiency and ensure the safety of oil and gas pipeline. A pig with improper geometry will easily get stuck in the pipeline and the attached electrical equipments may also be damaged by the crash, especially when passing through pipeline bends or elbows. This is not only harmful for the pig itself, but also threatens the transportation security of pipeline. In this paper, avoiding getting stuck in the pipeline bend, the detail process when the bi-directional pig passing through pipeline bend is discussed. The proper method for determining the geometry size of the pig body is proposed and displacement of the bi-directional pig when passing the bend is presented after a force analysis of the sealing discs. The related theories for the pig design can provide some references to determine the size of pig body and make an appropriate setup of discs.