Fracturing, missing, rescue and retrieve of inner inspection tool of gas pipeline

During the operation of the inner inspection tool in gas pipelines, it is vulnerable to sticking or local fracturing in the positions with higher resistance, e.g. pipe wall deformation, elbows and slopes, and consequently serious potential safety hazards are caused to the pipeline operation. Therefore, it is necessary to carry out positioning and rescue as quickly as possible. In this paper, four steps (i.e., reason analysis, interval positioning, scheme formulation, rescue and retrieve implementation) were carried out to retrieve the inner inspection tool which was locally fractured and lost in one certain SINOPEC gas pipeline. And it was retrieved safely and effectively in time. The following research results were obtained. First, under higher tensile force, the inner inspection tool is vulnerable to fracturing at the mechanical joints. Second, the lost inspection tool can be positioned accurately using the magnetic-signal detection instrument. And third, the pigging devices selected for the rescue shall be prepared specially according to the weight of the rescued equipment and the operation state of pipeline to make sure successful rescue in one trip. It provides the experience and reference for the rescue of inner inspection tools missing in gas pipelines.