Failure analysis of high-drop pipeline in the process of dewatering

A new built gas pipeline exploded twice in succession at the late stage of dewatering after the pressure test. On the basis of the field data and description, the hydraulic state of the pipe flow was deduced. Thereafter the mechanical model characterizing the motion of the liquid plug and the compressible flow dynamic model describing water hammer have been established. Development, propagation, reflection, transmission and interaction of water hammer wave have been presented by the models. The field phenomenon that a lot of water and gas spurted intermittently from the outlet could be explained by this study. The dangerous position prone to explosion is determined and accordant with the fact. It is found that the essential cause for the explosion is the restricted delivery capacity of the air compressor and the big elevation change of the pipeline, which lead to cavitation and column separation. The instantaneous ultrahigh pressure due to water hammer results in pipe explosion.