Field of the Invention

The present invention relates to apparatus for sealing leaks in fluid-carrying ducts or pipelines.

Background of the Invention

Pipes carrying fluid, such as water, are usually located underground. Leaks in water pipes can lead to reduced pressure in the pipeline as well as potential contamination of the water being carried in the pipes.

It is known from EP2902690 to use an untethered, ball-shaped sensor unit adapted to roll along the interior surface of a water-carrying pipeline. The sensor unit uses acoustic sensors to detect leaks and record their location, so that they can be investigated and repaired from the surface.

It is known from GB2465487 to both detect and seal leaks in oil pipelines using remote sealing elements which are deployed upstream of the leak and carried to the leak site in the fluid within the pipe. The sealing elements are designed such that they are drawn into the defect and subsequently seal the leak by blocking the hole. In one embodiment, the sealing elements comprise a malleable thixotropic putty which changes state over time from malleable to substantially solid. The sealing element is deployed part way through the curing process so that it undergoes a slow extrusion through the defect in the pipe, while completing the curing process to form a plug in the defect. In another embodiment, the sealing elements comprise a solid core surrounded by an outer coating of thixotropic putty. The malleable coating extrudes through the defect and draws the solid core into a sealing engagement with the hole. As the coating cures the hard core is held in position and prevented from falling out of the leak.

Sealing elements of the type described in GB2465487 are deployed remotely and pulled into the defect due to the pressure differential which exists at the leak site. It would be desirable to provide a buoyant sealing element which is more easily drawn into defects located along the pipeline.

Summary of the Invention

Accordingly, a first aspect of the invention provides a sealing element for use in a fluid- carrying pipeline comprising a substantially central core surrounded by a coating which is adapted to perform partial extrusion through an opening in a pipeline wall to seal the opening, wherein the density of the sealing element is substantially the same as the density of the fluid in the pipeline, and wherein the coating comprises a two-part epoxy putty, and each part of the two-part epoxy putty is present as a discrete element within the coating. Each part of the two-part epoxy putty may be provided in a separate layer.

One of the first and second parts of the two-part epoxy putty may be provided in a layer around the central core with the other of the first and second parts of the two-part epoxy putty being in the form of granules or particles disposed throughout or in the surface of said layer around the central core.

Preferably, the core is buoyant and preferably the density of the core is less than the density of the fluid in the pipeline.

The core may be hollow, for example the core may be a hollow ball filled with air. Alternatively, the core may be fabricated from a buoyant material. A suitable example material is expanded polystyrene. Preferably the core is deformable.

Preferably the fluid in the pipeline is water and the core has a density of less than lg/cm ³ .

Preferably the coating comprises a thixotropic putty.

The coating may be provided with a protective outer membrane. Preferably the outer membrane is fabricated from an elastomenc material such as rubber or latex. Preferably the outer membrane is flexible.

A second aspect of the invention provides a method of sealing a defect in a fluid-filled pipeline comprising the steps of:

i) kneading a sealing element according to any of Claims 1 to 8 to combine the two parts of the epoxy putty to begin the curing process;

ii) introducing a sealing element according to any of Claims 1 to 8 into the pipeline upstream of the defect;

iii) allowing the sealing element to be transported to the defect by the fluid contained within the pipeline; and

iv) allowing the sealing element to at least partially extrude through the defect and to cure wherein a part of the sealing element forms a solid plug located within the defect after extrusion through the defect and curing of the sealing element.

Preferably, the time taken for the part of the sealing element to cure is in the region of 10 to 20 minutes.

Preferably, the core of the sealing element does not come into sealing engagement with the defect.

The sealing element of the invention has a density less than or equal to the density of the fluid through which it is to travel, meaning that it is buoyant in that fluid. The buoyancy provides an improved sealing element which is more easily drawn into defects within a pipeline. Brief Description of the Drawings

In the drawings, which illustrate a preferred embodiment of the apparatus of the invention, and are by way of example:

Figure 1 is a schematic cross-sectional view of an example of a sealing element of the invention approaching a leak site in a pipe;

Figure 2 is a schematic view of the sealing element of Figure 1 when partially extruded through the leak site in the pipe;

Figure 3 is a schematic cross-sectional view of a sealing element according to a further embodiment of the invention approaching a leak site in a pipe;

Figure 4 is a schematic view of the sealing element of Figure 3 when partially extruded through the leak site in the pipe;

Figure 5 illustrates a cross-sectional view through a sealing element according to an embodiment of the invention; and

Figure 6 illustrates a cross-sectional view through a sealing element according to another embodiment of the invention.

Detailed Description of the Preferred Embodiments of the Invention

Figure 1 illustrates a cross-sectional view of an example of a substantially spherical sealing element 10 according to a first embodiment of the invention, shown inside a pipeline 16, in which there is a defect or hole 15.

The sealing element 10 includes a buoyant core 14 surrounded by a coating of epoxy putty 12. The putty changes state over time from malleable to substantially solid.

In this example, the buoyant core 14 is a polystyrene sphere with a diameter of between lmm and 5mm. The total diameter of the sealing element is preferably in the range 5 to 10mm.

A fluid 11, typically water, flows along the pipeline 16 in the direction of the arrow. The sealing element 10 is deployed into the pipeline 16 upstream of the hole 15. The sealing element 10 has a density substantially equal to the fluid being carried by the pipeline 16, meaning that the sealing element 10 travels easily along with the fluid 11.

The putty 12 comprises a two-part epoxy resin and the two parts must be mixed together to initiate the change in state from malleable to substantially solid. Two-part epoxy resins are commercially available. An example of a suitable commercially available epoxy putty has a specific gravity of 1.7. In Figure 1 the putty 12 is shown after mixing. Figure 5 illustrates an example of a sealing element before the two parts are mixed together. In this example, each part of the two-part epoxy resin is present in a separate layer 12a, 12b surrounding the core 14. The two layers are mixed by manual kneading of the sealing element 10 for 15 to 20 seconds prior to deployment into the pipeline 16. Mixing of the two layers 12a, 12b starts the curing process. Preferably the putty 12 cures in around 15 to 20 minutes after the initial kneading.

Alternatively, as shown in Figure 7, one part 12b of the two-part epoxy resin may be dispersed through the other part 12a of the two-part epoxy resin, for example in the form of a number of granules. As with the example shown in Figure 5, the two parts of the epoxy resin are combined by manual kneading to form a coating 12 in which both parts 12a and 12b of the putty 12 are combined.

The sealing element 10 is deployed when the putty 12 is combined and malleable. It is carried along the pipeline 16 by the fluid 11 towards the hole 15. The pressure differential at the hole 15 pulls the sealing element 10 towards the leak site. Since the putty 12 is in a malleable state it undergoes a slow extrusion into the hole 15. When the curing process is completed, the sealing element forms a permanent plug 13 in the hole 15 as shown in Figure 2. The putty 12 also exhibits adhesive properties which help the sealing element 10 to bond to the surfaces of the pipeline 16 around the hole 15.

As shown in Figures 2 and 4 it is the coating 12 and not the core 14 which forms the seal in the pipeline 16, sealing the hole 15.

Figure 3 illustrates another embodiment of the invention in which the sealing element 20 includes an outer membrane 18 over the putty 12. The outer membrane 18 is preferably elastomeric, and may be a thin layer of rubber or latex with a thickness of approximately 0.1mm. The outer membrane 18 may be applied by dipping the putty 12 into a liquid coating composition which air dries to form the coating 18. Where present, the outer membrane 18 protects the putty layer 12 of the sealing element 20 both before deployment and during deployment of the sealing element 20 in the pipeline 16. The outer membrane 18 needs to be flexible so that it extrudes through the hole along with the putty layer 12. Typically, the outer membrane 18 breaks as the sealing element is pulled into the leak.

As with the previous embodiment, the putty 12 comprises a two-part epoxy resin and the two parts must be mixed together to initiate the change in state from malleable to substantially solid. In Figure 3 the putty 12 is shown after mixing.

Figure 6 illustrates an example of the sealing element 20 before mixing. In this example, each part of the two-part epoxy resin is present in a separate layer 12a, 12b surrounding the core 14. The outer layer 12a is covered by the outer membrane 18. As with the previous embodiment, the two layers are mixed by manual kneading of the sealing element 10 for 15 to 20 seconds prior to deployment into the pipeline 16. Mixing of the two layers 12a, 12b starts the curing process. Preferably the putty 12 cures in around 15 to 20 minutes after the initial kneading.

Alternatively, as shown in Figure 8, one part 12b of the two-part epoxy resin may be dispersed through the other part 12a of the two-part epoxy resin in the form of a number of granules. The outer membrane 18 covers both parts 12a, 12b of the epoxy resin. As with the example shown in Figure 6, the two parts of the epoxy are combined by manual kneading to form a coating 12 in which both parts 12a and 12b of the putty are combined.