GB2246827A

GB2246827A - Pipe stopper

Info

Publication number: GB2246827A
Application number: GB9017375A
Authority: GB
Inventors: Kenneth Samuel Hemingway
Original assignee: International Pipeline Products Ltd
Current assignee: International Pipeline Products Ltd
Priority date: 1990-08-08
Filing date: 1990-08-08
Publication date: 1992-02-12
Anticipated expiration: 2010-08-08
Also published as: GB2246827B; GB9017375D0

Abstract

A pipe stopper 10 for use within a pipe section 11 in order to seal the internal wall surface thereof while maintenance or hydrostatic testing repair operations are carried out, includes an annular sealing device 12 and end plates 20. The sealing device 12 can be inflated so as to move radially outwardly into sealing contact with an inner annular surface 13 of the pipe section 11. The sealing device 12 comprises an inner annular member 14 and an outer annular member 15 which is bonded to the inner member 14 only along sunface 17 and may thus move radially away from the outer face 16 of the inner annular member 14. The pipe stopper 10 also includes a gripping device which may take the form of an annular friction band 18 or a profile (Fig. 3 not shown) arranged on the outer surface 19 of the outer annular member 15. The device 12 may be formed by coating the inner member 14 (e.g. from urethane), coating the outer face 16 with a release agent and then coating the outer member 15 onto member 14. <IMAGE>

Description

PIPE STOPPER This invention relates to a pipe stopper for use in sealing a pipe section while maintenance, or hydrostatic testing repair operations are carried out.

In this specification, the reference to a pipe section" is intended to include any length of pipe, a pipe joint or a pipe coupling.

The invention has been developed primarily, though not exclusively, in connection with a pipe stopper for sealing a pipe section against liquid pressure action, and particularly so as to withstand substantial differential pressure action across opposed faces of the pipe stopper.

In connection with the pressure sealing of liquids, it is most important that a pipe stopper should be able to carry out a dual function, namely first of all to carry out a proper sealing function to prevent liquid ingress or egress with respect to a pipe section, and secondly so as to resist any tendency for the pipe stopper to be axially displaced as a result of any differential pressure action across the stopper.

There is a particular demand for high integrity pipe stoppers to be available for use in the North Sea Oil industry, and also for use in sewer/water main applications, when maintenance and repair operations are required to be carried out in situ on a pipe section.

A known pipe stopper for use in sealing a pipe section comprises an annular sealing device which is inflatable so as to move into sealing contact with an annular surface of the pipe section. The sealing device comprises an inner annular member, and an outer annular member which is coaxial with the inner member. The sealing device is formed by first of all casting the inner annular member, and then casting the outer annular member onto the inner annular member such that the outer annular member is bonded to the inner annular member along the entire outer surface of the inner annular member. The sealing device is inflated by pressurising the inner annular member with a pressure medium such as water in order to radially expand the outer annular member to inflate the sealing device.

A problem with this known pipe stopper is that the process of radially expanding the outer annular member may require high pressures to be applied to the inner annular member.

According to a first aspect of the invention there is provided a pipe stopper for use in sealing a pipe section and comprising: an annular sealing device which is inflatable so as to move into sealing contact with an annular surface of the pipe section, the sealing device comprising: an inner annular member; an outer annular member coaxial with the inner member and bonded to the inner member, characterised in that the outer member is only partially bonded to the the inner member whereby the outer member is moveable radially relative to the inner member.

During inflation, the outer annular member may thus move away from the radially outer face of the inner member.

This facilitates the radial expansion of the outer tyre upon inflation.

The sealing device may be formed by casting the inner member, partially coating the inner member with a release agent and then casting the outer member onto the inner member. The release agent prevents bonding of the outer member onto the portion of the inner member on which the release agent was coated. The resulting sealing device may be easily radially expanded upon inflation to form a seal in a pipe section.

Preferably, the sealing device is inflated by using water or a mixture of water and glycol as the pressure medium. The sealing device may be inflated up to 1200 psi, which will allow the pipe stopper to hold a pipe line pressure of approximately 120 psi. Conveniently, the inner and outer members are each moulded from urethane.

Preferably, the pipe stopper further comprises a gripping device arranged to be moveable under the action of the inflation of the sealing device so as to make a gripping contact with the pipe section at the position near or adjacent to said annular surface enageable by the sealing device. The gripping device may be directly bonded to the outer annular member, and may take the form of a circular friction band, or a pair of axially spaced bands.

The friction band may have a gritted or otherwise roughened surface to engage the surface of the pipe section.

Alternatively, the gripping device comprises a profiled surface of the outer annular member.

Conveniently, the annular sealing device and the gripping device are held captive axially within a housing formed by a pair of axially spaced annular end plates, and the gripping device may engage directly with a moving surface of the annular sealing device.

According to a second aspect of the invention there is provided a method of forming a pipe stopper of the type comprising an annular sealing device which is inflatable so as to move into sealing contact with an annular surface of the pipe section, the sealing device comprising: an inner annular member; and an outer annular member coaxial with the inner member and bonded to the inner member, the method comprising the steps of: casting the inner member; and casting the outer member onto the inner member; characterised in that the method further comprises the step of coating a portion of the inner member with a release agent prior to casting the outer member onto the inner member whereby the outer member is only partially bonded to the inner member, such that the outer member is moveable radially relative to the inner member.

The invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a sectional illustration of an embodiment of a pipe stopper according to the invention, for use within a pipe section in order to seal and to engage the internal wall surface of the pipe section; Figure 2 is a sectional illustration of a second embodiment of a sealing device for use in the pipe stopper of figure 1; and Figure 3 is an illustration of a part of the outer surface of the sealing device of figure 2.

Referring to figure 1, a pipe stopper according to the invention is designated generally by reference 10 which is intended for use within a pipe section 11 in order to seal the internal wall surface thereof while maintenance, or hydrostatic testing repair operations are carried out. The pipe stopper 10 includes an annular sealing device 12 which can be inflated so as to move radially outwardly into sealing contact with an inner annular surface 13 of the pipe section 11. The sealing device 12 comprises an inner annular member 14 in the form of an inner tyre, and an outer annular member 15 in the form of an outer tyre. The inner tyre 14 has a radially outer face 16 and a radially inner face 17. The outer tyre 15 is bonded to the inner tyre 14 at the inner face 17. The outer tyre 15 may thus move radially away from the outer face 16 of the inner tyre. The sealing device is formed by casting the inner tyre 14, and then coating the outer face 16 with a release agent. The outer tyre 15 is then cast onto the inner tyre 14. The release agent ensures that the outer tyre 15 does not bond to the outer face 16, but only to the inner face 17 of the inner tyre 14. Both the inner tyre 14 and the outer tyre 15 are moulded from urethane. The pipe stopper 10 also includes a gripping device which in this embodiment takes the form of an annular friction band 18 arranged on the outer surface 19 of the outer tyre 15. The friction band 18 may take the form of a band having bonded grit or other suitable surface roughening to engage the internal surface of the pipe section.

The sealing device 12 and the gripping device 18 are held captive axially within a housing which is formed by a pair of axially spaced annular end plates 20, an internal sleeve 21 welded at each end to the end plates 20, and a hollow axial stub 22 which serves to convey liquid into or out of the pipe section 11. A valved inlet pipe 23 also extends axially through one of the end plates 20 and within the annular space defined between the stub 22 and sleeve 21, to connect with the interior of outer tyre 15 for inflation and deflation purposes.

In order to inflate the sealing device 12, water, or a mixture of water and glycol is pumped into the annular space 24, to a pressure of about 1200 psi. This causes the outer tyre 15 to expand radially, such that a gap 25 is created between the inner tyre 14 and the outer tyre 15.

Through the invention, the outer tyre 15 may move axially away from the inner tyre 14 on inflation of the sealing device 12. This results in easy radial expansion of the outer tyre upon inflation.

Referring to figure 2, an alternative sealing device is shown, in which the gripping device 18 comprises a profiled surface of the outer tyre 15. Figure 3 shows in more detail the profiled surface.

A pipe stopper according to the invention may be used in sewer/water main applications, where the pipeline typically has a diameter of three inches, and also in North Sea oil and gas applications where the pipelines typically have diameters of up to three meters.

Claims

1. A pipe stopper for use in sealing a pipe section and comprising; an annular sealing device which is inflatable so as to move into sealing contact with an annular surface of the pipe section, the sealing device comprising; an inner annular member: an outer annular member co-axial with the inner member and bonded to the inner member, characterised in that the outer member is only partially bonded to the inner member whereby the outer member is movable radially relative to the inner member.

2. A pipe stopper as claimed in claim 1 wherein the sealing device is formed by casting the inner member, partially coating the inner member with a release agent and then casting the outer member onto the inner member.

3. A pipe stopper according to claim 1 or claim 2 wherein the sealing device is inflated by using water or a mixture of water and glycol.

4. A pipe stopper according to any one of the proceeding claims wherein, in use, the sealing device has a pressure of up to 12 psi when inflated.

5. A pipe stopper according to any one of the proceeding claims wherein the inner and outer members are each moulded from urethane.

6. A pipe stopper as claimed in any one of the proceeding claims further comprising a gripping device arranged to be movable under the action of the inflation of the sealing device so as to make a gripping contact with the pipe section at the position near or adjacent to said annular surface engageable by the sealing device.

7. A pipe stopper according to claim 6 wherein the gripping device is directly bonded to the outer annular member, and takes the form of a circular friction band.

8. A pipe stopper according to claim 6 wherein the gripping device is directly bonded to the outer annular member and takes the form of a pair of axially spaced bands.

9. A pipe stopper according to claim 7 or claim 8 wherein the or each band has a gritted or otherwise roughened surface engageable with the surface of the pipe section.

10. A pipe stopper according to claim 7 or claim 8 wherein the gripping device comprises a profiled surface of the outer annular member.

11. A pipe stopper according to any one of claims 7 10 wherein the annular sealing device and the gripping device are held captive axially within a housing formed by a pair of axially spaced annular end plates, and the gripping device is engageable directly with a moving surface of the annular sealing device.

12. A method of forming a pipe stopper of the type comprising an annular sealing device which is inflatable so as to move into sealing contact with an annular surface of the pipe section, the sealing device comprising: an inner annular member; and an outer annular member co-axial with the inner member and bonded to the outer member, the method comprising the steps of; casting the inner member: and casting the outer member onto the inner member: characterised in that the method further comprises the step of coating a portion of the inner member with a release agent prior to casting the outer member onto the inner member whereby the outer member is only partially bonded to the inner member. such that the outer member is movable radially relative to the inner member.

12. A pipe stopper substantially as herein before described with reference to the accompanying drawings.

13. A method of forming a pipe stopper substantially as herein before described with reference to the accompanying drawings.