FOLDABLE, DOUBLE-BLOCK AND BLEED PLUGGING TOOL

摘要

An isolation tool (10) for temporarily isolating a section of pipeline has foldable semi-circular sealing element halves (17, 37) that, when unfolded, combine to form a primary and secondary sealing element (61, 67). The element halves (17, 37) unfold by rotating an inner bar (11) about the axis of an outer bar (31). A bleed hole (71) permits any fluid which leaks past the primary sealing element (61) and into the annular space between the sealing elements (61, 67) to enter a longitudinal bleed passageway (73) located within the tool (10) itself, thereby eliminating the need for a bleed port or valve to be welded onto the pipeline. The tool (10), which is pressure balanced, is well adapted for use in applications in which the lateral access opening is significantly smaller in diameter than the pipe diameter.