British Gas Plc

Lattice Intellectual Property Limited

Brian E McGuire

A lining method for a host pipe ( ) including lubrication of the host pipe prior to insertion of a thermoplastic liner ( ) using tight fit techniques. After allowing the inserted liner to relax, the liner is partially pulled from within the host pipe using puller ( ) and clamped with an internal clamp ( ) to allow fitting of a special flange ( ) to the liner ( ) by butt fusion, for example. Threafter the liner is allowed to revert so as to abut a flange ( ) fitted to the host pipe ( ). The technique is repeated at the other pipe end.

Pipe lining

A method of lining installed pipework which includes the steps of taking a length of liner pipe made from a memory retaining plastics material of external diameter greater than the internal diameter of the pipework to be lined, drawing the liner pipe through a swaging die which is attached directly or indirectly to the pipe to be lined using pulling means under tension attached to the leading end of the liner pipe and threaded through the pipework to reduce the external diameter of the liner pipe by up to 15%, the tension applied by the pulling means being such as partially to restrain the radial expansion of the outer surface of the liner pipe after its emergence from the die, drawing the liner pipe after its emergence from the die, drawing the liner pipe through the installed pipework with its outer diameter reduced to and/or maintained at a dimension less than that of the inner diameter of the pipework and thereafter allowing the liner pipe to expand within the pipework by relaxation of the said tension followed by memory induced expansion at ordinary atmospheric pressure and at the ambient temperature of the pipework.

Method for the lining of existing pipes

Cutting apparatus is provided for cutting a hole or `window` in the wall of a pipe, for example prior to joining a branch pipe to a host pipe. The apparatus comprises a chassis frame 14 carrying a cutter unit 42 supporting a cutter tool 62. The chassis is attached to and movable around the pipe 12 by means of `roller` chains 24. The cutter unit is movable with respect to the chassis frame by means of the associated slider block 38 which is slidable along longitudinally extending chassis frame members 16. Thus, the cutter tool 62 can be moved relative to the workpiece in one sense by movement of the chassis frame 14 and in another sense by movement of the cutter tool relative to the chassis frame. A combination of such movements enable the hole or `window` to be cut.

Method of and apparatus for cutting a pipe

Cutting apparatus is provided for cutting a hole or `window` in the wall of a pipe for example prior to joining a branch pipe to a host pipe. The apparatus comprises a chassis frame 14 carrying a cutter unit 42 supporting a cutter tool 62. The chassis is attached to and movable around the pipe 12 by means of `roller` chains 24. The cutter unit is movable with respect to the chassis frame by means of the associated slider block 38 which is slidable along longitudinally extending chassis frame which is slidable along longitudinally extending chassis frame members 16. Thus, the cutter tool 62 can be moved relative to the workpiece in one sense by movement of the chassis frame 14 and in another sense by movement of the cutter tool relative to the chassis frame. A combination of such movements enable the hole or `window` to be cut.

An apparatus for lining installed pipework which includes a swaging die which is attached directly or indirectly to the pipe to be lined, pulling structure attached to the leading end of the liner pipe and threaded through the pipework to reduce the external diameter of the liner pipe by up to 15%, pushing structure located between the die and the pipework, and heating and cooling apparatus for the liner pipe.

Apparatus for the lining of existing pipes

A trencher comprises a ground running, powered vehicle which travels in a forward direction carrying a trenching wheel driven by power to rotate in a vertical plane containing the forward direction so that cutting tips on the wheel's periphery excavate spoil from the ground leaving a trench therebehind. A plough just behind the front end of the trenching wheel pushes the spoil aside from the trench. The plough comprises two blades in V-shaped disposition, each blade being at a respective opposite side of the trenching wheel with leading ends of the plough blades being nearer sides of the wheel then their trailing ends. The plough blades, which are vibrated by vibrators driven by hydraulic motors, are mounted by elastically deformable anti-vibration mountings on respective supporting plates alongside the plough blades. The plough blades and these plates are raisable and lowerable hydraulically, and can be held braced in any desired V-shape by hydraulic struts.

Trencher

A liner 30 of polyethylene housing an SDR of 33 or less is pulled through a die 36 and through the pipe 10 and allowed to revert to the internal diameter of the pipe. The force of pulling is half the yield strength of the liner or less. The die has an entry; a throat and an exit, the entry decreasing in diameter towards the throat and the exit increasing in diameter away from the throat. The liner has a maximum diameter before the die, a minimum diameter in the die and intermediate diameter after the die. The liner bending inwards before first contacting the die at the entry, then continuously bending through its minimum diameter as it passes the throat and then undergoing die swell resulting in said intermediate diameter. The throat is defined by the merger in a continuous curve of a radius joining the entry and a radius joining the exit.

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Oldham, United Kingdom

Brian E McGuire