GB1576356A

GB1576356A - Plugging a pipeline

Info

Publication number: GB1576356A
Application number: GB1107977A
Authority: GB
Original assignee: PREMABERG GREAT BRITAIN Ltd
Current assignee: PREMABERG GREAT BRITAIN Ltd
Priority date: 1978-05-08
Filing date: 1978-05-08
Publication date: 1980-10-08

Description

(54) PLUGGING A PIPELINE (71) We, PREMABERG (GREAT BRITAIN) LTD., a British Company, of 22/24 High Street, Halstead, Essex C09 2AP, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to plugging a pipeline, and particularly, but not exclusively an undersea pipeline.

The invention provides a device for plugging a pipeline after insertion along the pipeline axis comprising a cylindrical distendable membrane made of resilient material, the membrane having conically tapered hemispherical or ellipsoidal ends and having rigid end closures, one such end closure having means for mounting a gas cylinder in a position in which it projects axially into the membrane for maintaining the distending pressure therein.

The cylindrical membrane may have frustoconical, ellipsoidal or hemi-spherical ends, and these ends may be protected by rigid caps.

The ends of the membrane may be circular openings with a wire bead moulded into the material of the membrane. The rigid end closures can then each comprise a pair of metal plates, each plate of a pair having an annular groove for receiving the bead. When respective pairs of plates are drawn together each pair grips a respective bead and forms a seal.

The membrane may be made from a rubber or synthetic rubber material reinforced with cross-ply fabric.

It is intended that the device be taken to pipelines wherever they may be 1aid but particularly to those laid on the ocean floor (down to about 600 ft) and inserted into an open end and inflated. The seal thus formed will resist the thrust developed by the differential pressure across the seal caused by pumping out fluid from one side only.

Similarly the device may be used to form a barrier between two fluids either at the same pressure or at unequal pressures the length of the device being chosen in proportion to the inequality of pressure external to the ends.

The device is thus intended to isolate sections of pipeline (a) being prepared for welding and (b) where for example a water and/or pressure tight housing is used to surround the submerged pipeline to allow work to proceed in air to atmospheric or hyperbaric pressures.

The invention will now be further described, by way of example, with reference to the accompanying drawing which is a fragmentary longitudinal cross-section through a pipe plugged by a device according to the invention.

Referring now to the drawing there is shown a pipe 1 containing a rubber membrane 2 of mainly cylindrical shape with tapered ends and reinforced by cross-ply fabric. Additional reinforcement may be provided at corners 3, and a wire bead 4 is moulded into the membrane at each end.

Each of these wire beads is gripped between a pair of plates 5, 6. Each plate has an annular groove 7 in it, and when the plates are bolted together, they retain the beads 4 and provide a seal therewith.

Compressed air or other high pressure gas or fluid is then admitted into the space within the device (e.g. through a filling valve 12). The membrane 2 then distends and seals against the pipe. Because of the pressure inside the device forcing the membrane against the pipe wall, a high friction is produced between the device and the pipe to prevent displacement of the device by pressure exerted in the pipeline on one side of the device.

A pressure controller 9 controls the pressure in the device and opens a cylinder 8 to admit more air or gas if the pressure should start to drop.

Alternatively, the device can be inflated to an initial pressure high enough to ensure that sealing is maintained over the period required, even though there may be some leakage over that period.

Rigid or semi-rigid caps 10 are mounted at each end of the device to provide support for, and prevent damage to, the membrane.

A conventional pressure relief valve 11 and also the already mentioned filling valve 12 are provided in one end cap.

The axial length of the sealing surface of the membrane is at least twice the inside diameter of the pipeline.

At the end of a repair operation, the device may be left inside the pipeline and must therefore be capable of being driven through the pipeline for recovery. Under the influence of increased pipeline pressure the device will deflate sufficiently to reduce friction and allow such movement. To contain ancillary equipment and to facilitate recovery it is convenient to attach this plugging device to a modified conventional pipe cleaning device known as a "Pig." In order to save weight, a standard pipe weld cap may replace the centre of the end plate 5.

WHAT WE CLAIM IS: 1. A device for plugging a pipeline after introduction along the pipeline axis, comprising a cylindrical distendable membrane made of resilient material, the membrane having conically tapered hemi-spherical or ellipsoidal ends and having rigid end closures, one such end closure having means for mounting a gas cylinder in a position in which it projects axially into the membrane for maintaining the distending pressure therein.

2. A device as claimed in claim 1 wherein said one such end closure comprises a chamber which extends axially into the membrane and contains a pressure regulator connected to a gas cylinder for controlling and maintaining the distending pressure in the membrane.

3. A device as claimed in claim 1 or claim 2 wherein each said end closure comprises a pair of plates each having an annular groove for sealingly gripping an annular bead at an end of the membrane, when the plates are fastened together.

4. A device as claimed in claim 1, 2 or 3 wherein the ends of the membrane are protected by rigid caps.

5. A device as claimed in any of claims 1 to 4 wherein the other such end closure includes a filling valve and a pressure relief valve.

6. A device for plugging a pipeline and constructed substantially as hereinbefore described with reference to, and as shown in, the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. to admit more air or gas if the pressure should start to drop. Alternatively, the device can be inflated to an initial pressure high enough to ensure that sealing is maintained over the period required, even though there may be some leakage over that period. Rigid or semi-rigid caps 10 are mounted at each end of the device to provide support for, and prevent damage to, the membrane. A conventional pressure relief valve 11 and also the already mentioned filling valve 12 are provided in one end cap. The axial length of the sealing surface of the membrane is at least twice the inside diameter of the pipeline. At the end of a repair operation, the device may be left inside the pipeline and must therefore be capable of being driven through the pipeline for recovery. Under the influence of increased pipeline pressure the device will deflate sufficiently to reduce friction and allow such movement. To contain ancillary equipment and to facilitate recovery it is convenient to attach this plugging device to a modified conventional pipe cleaning device known as a "Pig." In order to save weight, a standard pipe weld cap may replace the centre of the end plate 5. WHAT WE CLAIM IS:

1. A device for plugging a pipeline after introduction along the pipeline axis, comprising a cylindrical distendable membrane made of resilient material, the membrane having conically tapered hemi-spherical or ellipsoidal ends and having rigid end closures, one such end closure having means for mounting a gas cylinder in a position in which it projects axially into the membrane for maintaining the distending pressure therein.