| 摘要 |
A method for cutting an opening in the side of a pipe carrying gas under pressure, providing a bypass through the cut, and terminating the bypass when the pipe has been repaired, and apparatus for performing steps of the method. A branching saddle is bonded to the pipe, and a fixture is mounted on the pipe at the saddle. The fixture comprises a barrel through which various tool-insertion assemblies may be inserted. The tool-insertion assemblies typically include a shaft carrying a tool on one of its ends, a driving hub affixed near its opposite end, and a sealing plug slidably mounted axially on the shaft between the tool and the driving hub. The tools enter into the fixture's bore through a tool inlet, into which the sealing plug of the insertion assembly is screwed for a pressure-tight fit. The tools are individually inserted, in succession, through the fixture's bore and through the wall of the pipe. Lowering of the tools by means of the insertion assemblies into and out of the pressurized pipe is made possible by manipulation of a gate valve in the fixture, which allows the upper part of the bore to be depressurized prior to removal and during the insertion of different ones of the insertion assemblies.
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