| 摘要 |
A method is disclosed 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, along with apparatus for performing steps of the method. To provide the bypass, a branching saddle is bonded to the pipe, and a fixture is mounted on the pipe at the saddle. The fixture comprises a barrel having an inlet at one end, into which the pipe stub of the branching saddle extends, and a second inlet at its opposite end, through which various tool-insertion assemblies may be inserted, and an axial bore connecting the inlets. A gate valve, housed within a drum around the midsection of the barrel, is operable to divide the barrel so that the bore region in its upper part is pressure-isolated from that in its lower part. 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 it tool inlet, into which the sealing plug of the insertion assembly is screwed for a pressure-tight fit. Typically, one of the tools is a shell cutter, and another one is a bypass plug. They are individually inserted, in succession, through the fixture's bore and through the branching-saddle pipe stub, first, to cut, and later, to bypass, 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 the gate valve, 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. Through a primary, valved port in the side of the barrel, gas may be diverted from the pipe, through the fixture and through a conduit, to a similar fixture on the other side of the break. A secondary valve, in communication with the upper part of the barrel above the gate valve, permits depressurization of that part of the barrel during insertion and removal of the various tool-insertion assemblies while the gate valve is closed.
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