GB2335963A - Inflatable stopper - Google Patents

Abstract

An inflatable stopper 10 comprises a solid core 13 made of deformable material and an outer portion with two opposed end portions 11 joined by an annular cylindrical connecting portion 12 surrounding the core 13. A pressurised inflating medium, eg pressurised sea water, is routed via the core 13 into a pressure chamber 20 located in the annular connecting portion 12 to inflate it so as to form a contact seal with a pipe inner wall. The solid core 13, and preferably the outer portion 11,12, are made of a deformable material which undergoes only a small volume change upon deformation. The pressure chamber 20 is designed so that on inflation its radially inner wall 21 applies an inward force to the core 13 and its radially outer wall 22 applies an outward force to press pipe contacting surface 15, which is preferably a resilient tyre with a ribbed surface, against the inner wall of the pipe. Preferably, the outer portion 11,12 is made of a one piece moulding, and both the core 13 and outer portion 11,12 are formed around pressure line 17,19 by placing the pressure line 17,19 in a mould. The pressure chamber 20 is preferably annular and may include a solid member 23 to keep the walls 21,22 apart. There may be just one pressure chamber 20 as shown, or a plurality of pressure chambers (120, figure 2) may be provided. Each of these pressure chambers (120, figure 2) may have a respective annular tyre associated with it, or one tyre may overlie all of the pressure chambers (120, figure 2). The stopper 10 may be designed so that its relative density is approximately 1, preferably by making the core 13 from syntactic foam.

Description

2335963 INFLATABLE STOPPER This invention relates to an inflatable stopper

for use in sealing a length of pipe.

Inflatable stoppers are used to create temporary seals in pipelines and other f luid-conveying lines, or in inlet or outlet pipe fittings leading to storage vessels. The stoppers serve to prevent escape of f luid into and / or out of the temporarily sealed line etc.

one example of use, where high pressure seals are required, is in application of temporary seals to seabed pipelines for conveying fluid hydrocarbons, and a stopper used in such environments is often referred to as a llhyperbaric pig". When it is desired to weld two pipe lengths together on the seabed, a dry habitat is created around the pipe ends and a welder in the habitat then welds the pipe ends together e.g. by use of a cylindrical connecting piece welded together at each end to the facing pipe ends. However, although a dry habitat is created so that welding of butting pipe ends can take place, it is also necessary to seal the interior of the pipe ends so that pipeline fluids e.g. sea water cannot enter the dry habitat via the pipe ends.

One known type of hyperbaric, pig for such use is generally spherical in shape, and has a central annular portion which, upon inflation of the pig, expands radially outwardly into sealing contact with the inner wall of the pipeline to be sealed. Given the generally spherical shape of the pig, namely two hemispherical end portions joined together by the central annular portion, inflation of the pig (which is hollow) would tend to cause generally radial expansion of the outer wall of the pig. However, since radial expansion of the hemispherical ends would not exert any sealing function, the pig is provided with internal axial restraint between the opposed hemispherical ends e.g. in the form of a tie rod, and therefore upon inflation of the pig with an inflating medium e.g. pressurised water, the only part of the outer wall of the pig which is allowed to expand is the central annular portion. This therefore concentrates the expansion of the pig in this region, which gives rise to an effective sealing action with the wall of the pipeline, even in cases in which the wall surface is rough or uneven, or has weld metal projecting inwardly of the wall surface.

The axial restraint has to be built-in within the hollow interior of the pig, and to be able to exert a tensile force between the opposed hemispherical end portions, via suitable anchor fittings secured to, or embedded in the wall of the hemispherical end portions. This provides a complicated assembly, and with corresponding increased cost, when compared with the construction costs of what is basically an inflatable stopper.

The central annular portion may be provided with a so-called "waffle" pattern to improve the sealing contact with the wall of the pipeline, in that high pressure sealing contact takes place along the lines of the waffle pattern and in addition the sealing engagement of the waffle line contacts provide substantial axial frictional resistance to any tendency of the pig to move lengthwise of the pipeline under application of differential pressure thereto.

obviously, once the pipe ends have been welded together in the dry habitat, the two pipeline stoppers are trapped within the welded pipeline section now formed, and therefore have to be removed, usually by well known "pigging" methods. However, the axial restraint built-into the pigs, (which is effective in providing concentrated expansion of the pig along the sealing area where it is required), can cause severe operational difficulties during the subsequent expulsion of the pig. In extreme cases, this can result in the internal axial restraint elements being displaced through the wall of the pig, and being forcibly engaged with the wall of the pipeline, and given that usually there are some metallic components within this restraint system, this scratches or gouges the surface of the pipeline, which is clearly undesirable, quite apart from exerting substantial resistance to expulsion of the pig. The i protruding axial components may even cause the sealing pig to become trapped e.g. at a pipeline connection to a lateral, or any other part of the pipeline where the pipeline contour changes abruptly e.g. a pipe bend.

There is therefore a need to provide an improved design of inflatable stopper, which still has the advantage of providing localised expansion of the pig upon inflation, at areas where sealing pressure is to be concentrated, but having simplified construction and assembly, and easy expulsion subsequently.

According to the invention there is provided an inflatable stopper having two opposed end portions and a generally cylindrical connecting portion, said stopper being positionable in a pipe and being operable so that, upon inflation, the cylindrical portion is movable radially outwardly into sealing contact with the internal wall of the pipe, in which the stopper comprises:

a solid core made of deformable material which undergoes small, or substantially nil volume change upon deformation; an annular portion surrounding said core and forming said cylindrical connecting portion, said annular portion having an outer pipe wall sealing surface; control means for controlling the admission, and the exhaust, of a pressurised inflating medium relative to the stopper; an internal pressure line communicating with said control means and routed through said core and into said annular portion; and a pressure chamber in said annular portion having radially inner and outer walls and communicating with said pressure line so that, upon admission of the inflating medium, the inner wall of the chamber applies an inward force to the core and the outer wall applies an outer force which is effective to press the outer pipe wall sealing surface of the annular portion into sealing contact with the wall of the pipe.

The inner chamber wall therefore exerts an inward force in a direction towards the solid core, and therefore sets up a compressive load on the material between the chamber wall and the core, which results in the major part of the inflation effect being transmitted into outward expansion of the outer surface of the annular portion.

The invention therefore provides,a simple assembly of stopper (which is substantially solid internally), and which concentrates the inflation of the stopper into the area where it is required, namely the outer pipe wall engaging surface of the annular portion. Furthermore, by routing the admission of inflating medium through a pressure line in the core and outwardly to the chamber, little or no axial separating force is applied to the opposed end portions of the stopper, and therefore no internal strengthening tie structure is required.

Accordingly, subsequent expulsion of the stopper is facilitated and with lessened risk of rupture of the stopper arising, especially as it is not hollow, but is substantially solid internally, and without internal reinforcement.

Preferably, the end portions and the annular portion comprise a one piece moulding formed around the core, and this one piece moulding also may be made of a deformable material which undergoes little or no volume change upon deformation.

The routing of the inflating medium internally of the stopper may be achieved by provision of suitable pressure lines and connections, placed in a mould so that the core and/or the one piece moulding are formed around the pressure lines and connections.

The pressure chamber is preferably an annular chamber, and an annular tyre may be secured to the outer periphery of the annular portion to form a suitable pipe wall engaging member. Preferably, the tyre is capable of yielding resiliently under load, so as to improve the sealing action against the pipe wall.

More than one pressure chamber may be provided, axially spaced from each other, and each chamber may have a respective annular tyre associated therewith, or a common longer tyre may be provided to overlie all of the chambers.

Preferred embodiments of inflatable stopper according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a longitudinal cross sectional view of a first embodiment of inflatable stopper according to the invention, having a solid cylindrical core, and a single pipe wall engaging surface formed by an annular tyre located substantially centrally of the stopper on its outer periphery; Figure 2 is a view, similar to Figure 1, of a second embodiment having two axially spaced tyres located centrally of the outer periphery of the stopper; Figure 3 shows a third embodiment, with a different arrangement of axially spaced tyres; and Figures 4 to 6 are views, corresponding respectively to Figures 1 to 3, and showing further preferred embodiments.

Referring to the preferred embodiments shown in the drawings, an inflatable stopper is provided, which may comprise a 11hyperbaric pig", of the type used to seal temporarily sea bed pipe line ends, and in which the stopper has two opposed end portions which are hemispherical, or part spherical, and a generally cylindrical connecting portion. The stopper is positioned in a pipe and is operable so that, upon inflation, the cylindrical portion is moveable radially outwardly into sealing contact with the internal wall of the pipe.

Each embodiment of stopper comprises a solid core made of deformable material which undergoes little, or substantially zero volume change upon deformation. An annular portion surrounds the core and forms the cylindrical connecting portion, the annular portion having an outer pipe wall sealing surface.

Control means e.g. inlet and outlet valves, are provided to control the admission and the exhaust of a pressurised inflating medium relative to the stopper.

An internal pressure line communicates with the control means and is routed through the core and into the annular portion. A pressure chamber is formed in the annular portion and has radially inner and outer walls, and also communicates j 1 with the pressure line so that, upon admission of the inflating medium, the inner wall of the chamber applies an inward force to the core and the outer wall applies an outward force which is effective to press the outer pipe wall sealing surface of the annular portion into sealing contact with the wall of the pipe.

Referring now to Figure 1 of the drawings, the first embodiment of stopper is designated generally by reference 10 and comprises two opposed end portions 11 and a generally cylindrical connecting portion 12. A solid core 13 is made of deformable material, undergoing substantially no, or little volume change upon deformation, and an annular portion 14 surrounds the core 13 and has an outer pipe wall sealing surface located centrally of the stopper, and formed in this embodiment by a single tyre 15. As shown, the tyre 15 has a ribbed surface, to make sealing contact with the wall of the pipe, and with this arrangement, satisfactory sealing engagement is achieved, even in the case of a pipe wall having surface roughness or unevenness, or inward protrusion of weld metal. If desired, the tyre 15 may have an external "waffle" pattern if required. The tyre also is preferably capable of resilient yielding to some extent, to improve the sealing contact with the pipe wall.

Control means 16 e.g. inlet and/or outlet valves control the admission, and the exhaust of pressurised inflating medium e.g. pressurised sea water, relative to the stopper 10.

An internal pressure line 17 communicates with the control means 16, and as shown is routed through the core 13, along a first axially extending section 18, and then is routed radially outwardly through a connecting pipe section 19 and into the annular portion 14.

An annular pressure chamber 20 is formed in the annular portion 14, and has radially inner wall 21 facing the core 13, and radially outer wall 22 facing the tyre 15. If required, a solid annular member 23 may be located in the chamber 20, to hold the walls 21 and 22 apart radially, but permitting inflating medium entering the chamber 20 via discharge head 24 (at the radially outer end of pipe section 19) to make pressure contact with the inner and outer walls 21 and 22.

Therefore, upon admission of the inflating medium to the chamber 20, the inner wall 21 applies an inward force to the core 13, indirectly via a compressive load applied to the annular part of portion 14 located between chamber 20 and the outer surface of the core 13. By virtue of the substantially solid internal construction of the stopper, and choice of suitable deformable material for the core 13 at least, the major part of the inflation effect is transmitted into outward expansion of the annular portion 14, and therefore of the pipe wall engaging surface, namely tyre 15.

Therefore, with a simple assembly of stopper which is substantially solid internally, the inflation of the stopper is concentrated into the area where it is required, namely the outer surface of tyre 15. Furthermore, by routing the admission of the inflating medium through pressure line 17 in the core 13, and outwardly to the chamber 20, little or no axial separating force is applied to the two opposed end portions 11 of the stopper, and therefore no internal strengthening tie structure is required.

Therefore, after the temporary sealing of the pipe is no longer required e.g. after completion of a butt welded pipe joint, the stopper can be expelled, with lessened risk of rupture of the stopper arising, because it is not hollow, and also because it lacks any internal reinforcement.

Conveniently, the end portions 11 and the annular portion 14 are moulded in one piece around the core 13, and may be made of a deformable material which also undergoes little or no volume change upon deformation. In practice, it is preferred that the one piece moulding is slightly more yielding resiliently under load, compared with the core 13.

The routing of the inflating medium is achieved by provision of the pressure line 17 and appropriate connections, and which may be placed in a mould so that the core 13 and/or the one piece moulding (11, 14) are moulded around the pressure lines and connections.

-8 As shown in the embodiment of Figure 1, a single annular pressure chamber 20 is provided, and an associated single tyre 15 is provided, which overlies the chamber 20, substantially throughout its axial extent.

However, other arrangements of pressure chamber (s) and tyre(s) may be provided, as will now be described with reference to the embodiments shown in Figures 2 and 3.

Referring to Figure 2, parts generally corresponding with those already described and shown in Figure 1 are given the same reference numerals, but with the addition of 100. The stopper 110 is different from stopper 10, in that two axially spaced inflation chambers 120 are provided, each of which has an associated pressure line 119 communicating therewith, and the inner wall 121 of each chamber 120 applies a radial inward compressive load, which is ultimately resisted by the core 113, but in this embodiment the radially outer wall 122 applies a radial outward expansion force directly to a moulded-in respective tyre 115, as shown.

Therefore, in this embodiment, two axially spaced inflation chambers 120 are provided, and each being associated with a respective tyre 115, which overlies it substantially, and which receives a radial expansion force which is applied directly thereto.

The third embodiment shown in Figure 3 is designated generally by reference 210, and is generally similar to the embodiment of Figure 2, and the same parts are therefore given the same reference numerals.

In this embodiment, there are two pressure chambers, reference 220 as shown, but which have radial depth which decreases in axial direction, as shown. The radially inner wall 221 still applies radially inwardly directed force, towards the core 113, whereas the radially outer wall 222 applies a radially outward force to a respective outer tyre 215, (of lesser depth than tyres 115), but also moulded-in position in the central portion of the outer surface of connecting portion 212. It has been found that a favourable alteration in the sealing pressure applied to the tyres 215 can be achieved, by virtue of the shape imparted to the chambers 220, which have cross section which increases with respect to axial direction towards each other.

The embodiments shown in Figures 1 to 3 have solid cores 13 and 113, made of moulded deformable material. However, while this provides necessary resistance to withstand compressive forces under water at depth, this material necessarily results in the overall stopper having a relatively high density. This means therefore that the net weight of the stopper of Figures 1 to 3, in water, is substantial, and therefore it can make it difficult to handle under water, especially at great depths. It is not unusual for stoppers to be utilised in pipelines on the seabed at depths of up to 600 metres, giving rise to very substantial water pressures.

With a view to reducing the overall density of the stopper, preferred developments of the embodiments of Figures 1 to 3 are shown in Figures 4 to 6 respectively. Parts corresponding with the previously described embodiments are given the same reference numerals, and will not be described in detail again.

In the embodiment of Figure 4, the core 13a is preferably made of syntactic foam, which has necessary compressive strength to withstand compressive forces at substantial depths under water, while being of such a density as to reduce the overall density of the stopper 10 substantially e.g. to a density of perhaps 1.2, thereby resulting in the net weight of the stopper being small, and making it more easily handled under water.

In the embodiments of Figures 5 and 6, cores 113a are shown, also made of syntactic foam.

However, while syntactic foam is one preferred material having necessary compressive strength, while giving sufficient reduction in the overall density to the stopper, it should be understood that other suitable low density and high strength materials may be used.

Claims (15)

CLAIMS:

1. An inflatable stopper having two opposed end portions and a generally cylindrical connecting portion, said stopper being positionable in a pipe and being operable so that, upon inflation, the cylindrical portion is movable radially outwardly into sealing contact with the internal wall of the pipe, in which the inflatable stopper comprises: a solid core made of deformable material which undergoes small, or substantially nil volume change upon deformation; an annular portion surrounding said solid core and forming said cylindrical connecting portion, said annular portion having an outer pipe wall sealing surface; control means for controlling the admission, and the exhaust, of a pressurised inflating medium relative to the stopper; an internal pressure line communicating with said control means and routed through said core and into said annular portion; and a pressure chamber in said annular portion having radially inner and outer walls and communicating with said pressure line so that, upon admission of the inflating medium, the inner wall of the pressure chamber applies an inward force to the core and the outer wall applies an outer force which is effective to press the outer pipe wall sealing surface of the annular portion into sealing contact with the wall of the pipe.

2. A stopper as claimed in claim 1, in which the end portions and the annular portion comprise a one piece moulding formed around the core.

3. A stopper as claimed in claim 2, in which the one piece moulding is made of a deformable material which undergoes little or substantially no volume change upon deformation.

4. A stopper as claimed in claim 2, in which the one piece moulding and/or core have been formed around the pressure line by placing the pressure line in a mould.

5. A stopper as claimed in claim 1, in which the pressure chamber is an annular chamber.

6. A stopper as claimed in claim 1, in which an annular tyre is secured to the outer periphery of the annular portion to from a suitable pipe wall engaging member.

7. A stopper as claimed in claim 6, in which the tyre is capable of yielding resiliently under load, so as to improve the sealing action against the pipe wall.

8. A stopper as claimed in claim 1, and having more than one pressure chamber.

9. A stopper as claimed in claim 8, and each pressure chamber having a respective annular tyre associated with it.

10. A stopper as claimed in claim 8, and having an annular tyre overlying all of the pressure chambers.

11. A stopper as claimed in claim 1, in which the relative density of the stopper is substantially 1.

12. A stopper as claimed in claim 1, in which the relative density of the stopper is not greater than 1.2.

13. A stopper as claimed in claim 1, in which the density of the core is such as to make the relative density of the stopper substantially 1.

14. A stopper as claimed in claim 1, in which the core is made of a foam.

15. A stopper as claimed in claim 14, in which the foam is syntactic foam.