Abstract: There is described an improved pipeline isolation tool for plugging a pipeline at a predetermined location, comprising a housing adapted for movement through a pipeline, the housing having first and second ends, seals disposed annularly about the housing, the seals being radially expandable into fluid sealing contact with an inner wall of the pipeline, and a plurality of braking members including grips for frictionally engaging the inner wall of said pipeline to lock the isolation tool in position against fluid pressure in the pipeline, the braking members being selectively and repetitively movable between a first position in which the grips are disengaged from the inner pipeline wall and a second position in which the grips engage the inner wall.