Plugging system for use during an offshore pipeline laying operation

1. Plug for use during operations of laying a pipeline, for sealing off a pipeline in case of water ingress into the pipeline, comprising sealing and gripping means, actuation means moving the sealing and gripping means from a retracted to an extended position and a control system for operation of the actuation means, wherein the control system comprises a sensor for detecting conductivity of the fluid around the plug and a control valve device wherein the actuation means comprises a pressure vessel and a piston/cylinder arrangement for operation of the sealing and gripping means in response to a given value of fluid conductivity being reached.

2. Plug according to claim 1 , wherein the gripping means comprises slip segments arranged around a partly conical shaped surface of a main body of the plug.

3. Plug according to claim 1 , wherein the slip segments in an outer surface comprise a means for enhanced friction relative to an inner surface of a pipeline.

4. Plug according to claim 1 , wherein the sealing means comprises an annular packer element.

5. Plug according to claim 1 , wherein the pressure cylinder comprises a pressurized nitrogen gas.

6. Plug according to claim 1 , wherein the piston/cylinder arrangement is positioned centrally within a main body of the plug.

7. Plug according to claim 1 , wherein the plug is autonomous.

8. Plug according to claim 1 , wherein it is connected to a pipeline tractor unit for positioning of the plug in the pipeline relative to the seabed and vessel.

9. Use of the plug according to claim 1 , during laying of a pipeline at large water depths.