The blockage risk in the elbow of the Bi-directional pig used for submarine pipeline based on the modified Burgers-Frenkel (MB-F) model

Abstract

The blockage accident is a knotty problem for the pigs employed in pipeline inspection and dewatering operations. Compared with the onshore pipeline, the rescue operation of the blocked pig in the submarine pipeline is extremely difficult and needs enormous costs. It is important to evaluate the blockage risk of the pig when passing through the elbow, which is beneficial for ensuring the security of the pipeline and the pig. However, the blockage risk assessment in current engineering practice mainly relies on the structure size examination and experience judgment. In this paper, a novel dynamic analysis model which describes the traveling attitude and force state of the pig in the elbow is derived based on the modified Burgers-Frenkel (MB-F) model. Four typical blockage forms were introduced on the basis of a quantitative index system established according to the pig frictional contact characteristics after a series of calculations. In addition, a quantitative assessment method for predicting the blockage risk of the bi-directional pig was presented through the weighting approach of subjective and objective evaluation using the analytic hierarchy process (AHP) and entropy combinational method. Then, the sensitivity analysis was conducted to determine the importance and the influence rules of the different factors.