GB2267545A

GB2267545A - Sealing of pipe joints

Info

Publication number: GB2267545A
Application number: GB9310242A
Authority: GB
Inventors: Alec Reginald Carruthers
Original assignee: ALH Systems Ltd
Current assignee: ALH Systems Ltd
Priority date: 1992-06-04
Filing date: 1993-05-18
Publication date: 1993-12-08
Also published as: GB9310242D0

Abstract

A sleeve method for sealing joints (16) in a pipe (10) comprises positioning a sleeve (28) inside a pipe (10) over the joint to be sealed, sealing the ends of the sleeve against the inside of the pipe either side of the joint to be sealed, supplying sealant into the void or recess formed by the sleeve, the sealed ends of the sleeve (26) and the inside surface of the pipe, and allowing the sealant to set Apparatus for carrying out this method preferably comprises a generally cylindrical inflatable bladder (18), the middle position of which forms the sleeve (28) while the ends form sealing members (26). Preferably the bladder is mounted on a flexible tube (20) which can be inserted into a pipe and through which sealant and gas for inflating the bladder may be supplied. <IMAGE>

Description

SEALING OF PIPES The present invention relates to sealing of joints, such as, for example, joints in a pipe such as a gas main.

A common way of sealing joints in a gas main is to insert, via a hole prepared in the main, a delivery tube having at its end a joint locating device and a spraying means. The delivery tube is pushed along the main until the spraying means lies at a joint. A sealant fluid is then forced through the delivery tube and is sprayed onto the joint by the spraying means.

The spraying means normally comprises a head mounted on the end of the delivery tube, which head rests at the bottom of the main. Sealant is sprayed at the roof of the main, and runs down around the edge, giving a complete seal. Such a system is described in our application published as GB2247062.

Although this system has been demonstrated to be highly successful, there is still room for improvement. It has been noted that; (i) The sealants generally used are of the anaerobic type and are relatively expensive fluids.

Depositing these fluids by spraying is inefficient as much of the sealant misses the vital area, which must be traversed to ensure wetting, and is wasted.

(ii) In small mains the excess fluid can settle into pools in the main where it cures. This can cause restriction of flow, and also prevent deployment of equipment, i.e. during surveys, flow stopping etc.

(iii) Where spraying takes place in the proximity of plant such as filters, governors and meters, the sealant may be transported in the gas stream under certain conditions, and contaminate the equipment causing malfunction.

(iv) Reliance on the spraying method to provide a 100 seal is not realistic. The flow of sealant into the leakage path depends largely on gas pressure and flow. Thus at low gas pressure only superficial wetting of the area can be expected without the penetration necessary to ensure a perfect seal.

At its most general, the present invention proposes that sleeve be provided which is movable along the interior of the pipe and the ends of which are sealable to the pipe. If the sleeve is then positioned so that it overlaps the location of the joint to be sealed and is sealed to the pipe, sealant may be supplied between the sleeve and the pipe and the sealant will be forced into the joint. Thus, the supply of sealant is constrained to the location of the joint. Therefore, the amount of sealant needed is minimised, and the sleeve prevents sealant from falling to other parts of the pipe, where it is not wanted.

Preferably, the sleeve is cylindrical, and may then define a cylindrical void or recess adjacent the interior of the wall of the pipe.

It is preferable that the seals for sealing the sleeve to the walls of the pipe are provided by inflatable members, since this allows the sleeve to be moved freely in the pipe when those members are not inflated. Suitable detection means may then be provided on or adjacent the sleeve for ensuring that the sleeve is located at the joint before the members are inflated. Alternatively, however, resilient seals may be used, provided they provide sufficient sealing force to resist escape of sealant.

In a further development, the sleeve and sealing members are formed by walls of an inflatable bladder mounted, eg, on the sealant delivery duct. Then, inflation of the bladder seals the ends of the sleeve to the interior of the pipe. Furthermore, if the sleeve is of resilient material, the internal pressure within the bladder may assist the forcing of the sealant into the joint.

Sealant may then be supplied to the void or recess by a suitable supply tube communicating with the recess. When sealant is pumped into the recess, through such a tube, it will move from the point of communication of the tube with the recess around the cylindrical recess. If the recess is otherwise wholly closed, the gas within the recess will become pressurised and may prevent the sealant spreading wholly around the sleeve at the joint. Some gas may escape through the joint itself, but it is preferable to provide an outlet duct leading from the recess at a point remote from the entry to the recess of the sealant supply tube. That outlet duct may, for example, lead into the interior of the bladder (where that method of sealing the sleeve is used) and then extend out of the bladder as a part of the bladder away from the walls of the pipe. For example, the outlet may be along the axis of the pipe.

It has previously been mentioned that a suitable detector may be provided in order to position the sleeve adjacent the joint. Furthermore, an angular position sensor may also be provided to give the sleeve a particular orientation within the pipe, eg to ensure that sealant is delivered to the lowest part of the pipe and so be forced upwardly at the joint.

It is should be noticed that the present invention relates to both method and apparatus aspects of sealing of joints.

An embodiment of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which; Fig. 1 is a cross-section through a gas main containing a joint sealing apparatus according to the present invention; Fig. 2 is a section on Il-Il of fig 1; Fig. 3 is a plan view of the section of fig 2, in the direction III shown on fig 1; Fig. 4. is a cross section through a gas main at the point at which a joint sealing apparatus according to the present invention is inserted, showing a joint sealing apparatus according to the present invention being inserted.

Referring to Fig 1, a main 10, for eg gas, has two pipe sections 12, 14, which define a joint 16, which is to be sealed. Inserted into the main 10 is an inflatable bladder 18 clamped to a delivery tube 20 by clamps 22. The bladder is inflated by nitrogen from a supply line 24 carried to the bladder 18 within the delivery tube 20.

The bladder has sealing panels 26 which are pressed against the walls of the pipe sections 12, 14 by the inflation of the bladder 18, to form a seal.

The sealing panels are in the form of two cylinders either side of the joint 16. Between the sealing panels 26, and thus facing the joint 16, is a centre panel 28 whose outside diameter is less than that of the sealing panels 26. This may be by a local reduction of the bladder wall diameter, or by constructing suitable seams within the bladder. Thus, a recess 29 is formed by the centre panel 28, the sealing panels 26 and the pipe sections 12, 14. This recess may be positioned about the joint 16 by interpreting the signals from a joint locating device 30, which will have a signal cable 32 which may be carried to the bladder 18 within the delivery tube 20.

Communicating with the recess 29 is a sealant supply tube 34. Sealant may thus be forced into the recess, sealing the joint. The sealant supply tube 34 may be carried to the bladder 18 within the delivery tube 20.

The joint locating device 30 may also contain an angular displacement indicator. Thus, the rotational orientation of the bladder 18 may be deduced and the bladder 18 rotated via the delivery tube 20 to ensure that the sealant supply tube 34 delivers sealant to the bottom of the recess 29. Thus, gas within the recess 29 will be forced to the top of the recess where it will bleed through the then unsealed joint 16. Shown in Fig. 1 is a gas bleed tube 36 which connects the top of the recess 29 and the interior of the main 10. This allows gas within the recess 29 to escape more easily.

Also shown in Fig. 1 are openings 38 in the walls of the delivery tube 20, upstream of the bladder 18.

The delivery tube 20 extends through the bladder 18 and has an open end 40 downstream of the bladder 18.

Thus, gas flowing through the main 10 may bypass the bladder 18 by passing through the openings 38, along the delivery tube 20, and out of the open end 40, as shown by arrows 42. This enables use of the bladder without interrupting gas flow through the main 10.

The gas bleed tube 36 may then vent into the delivery tube 20.

Figs 2 and 3 show in more detail the joint locating device 30, which (in this embodiment) is similar to that described in GB2235302. A sensing device 50 is enclosed within a pocket formed by the wall of the bladder 18 and a cover 52. The sensing device 50 contains a number of sensors 54 which detect the position of the joint 16 relative to the sensing device 50 (and thus the bladder 18).

Also fitted to the joint locating device 30 is an angular displacement indicator 56 which senses the angular orientation of the joint locating device 30 (and thus the bladder 18). Terminal 58 allow communication between the joint locating device 30 and information display means (not shown) via signal cable 32 (shown in Fig. 1).

Fig. 4 shows in diagrammatic form an arrangement for effecting the insertion of the delivery tube 20 and bladder 18 into the main 10 which (in this embodiment) is similar to that disclosed in co-pending application No: 9201619.5. There is provided a sleeve 70 which may be attached around a main 10, enclosing a region 71 about a length of the main 10. A hole 72 may then be formed in the main 10, within the length enclosed by the sleeve 70. The region 71 within the sleeve 70 may be accessed via a valve 73.

The sleeve 70 has two alternative entry tubes 74 each of which extends at one end into the region 71 enclosed by the sleeve 70, and is closed at its other end by a valve cap 76. The tubes 74 are directed in opposing directions to allow insertion of the delivery tube 20 in either direction along the gas main 10.

The valve cap 76 is adapted so as to allow the delivery tube 20 and attached bladder 18 (un-inflated) to pass through it, and hence along an entry tube 74, into the enclosed region 71 and through the hole 72 into the main 10. If this arrangement is used, the delivery tube 20 should be flexible enough to allow insertion into the main 10 via hole 72 and subsequent bending until parallel to the main 10. A material such as polypropylene generally allows sufficient flexibility for this.

Claims

1. A method of sealing a joint in a pipe comprising the steps of: inserting a sleeve within the pipe; positioning the sleeve so that it covers the joint; sealing the ends of the sleeve to the inside surface of the pipe on opposite sides of the joint; supplying sealant between the sleeve and the inside surface of the pipe; and causing the sealant to set so as to seal the joint.

2. A method according to claim 1, wherein the positioning of the sleeve includes detecting the position of the joint relative to the sleeve, and moving the sleeve so that it covers the joint.

3. A method according to claim 1 or claim 2, wherein the sealant is supplied at the lowest part of the sleeve and forced away from that lowest part around the sleeve.

4. A method according to any one of the preceding claims, wherein the sealant is supplied at a single point of -the sleeve

5. A method according to claim 4, further including detecting the orientation of the sleeve in the pipe, so as to determine the location of the point of supply of the sealant.

6. A method according to any one of the preceding claims, wherein the sleeve is cylindrical and defines a void at the location of the joint when it is sealed to the pipe, the sealant being supplied to that void.

7. A method of sealing a joint substantially as any one herein described with reference to the accompanying drawings.

8. An apparatus for sealing a joint in a pipe comprising: a sleeve; means for moving that sleeve within a pipe; sealing means at the ends of the sleeve for sealing the sleeve to the pipe; and means for supplying sealant through the sleeve to the external surface of the sleeve for sealing the joint.

9. An apparatus according to claim 8 wherein the sleeve is cylindrical.

10. An apparatus according to claim 7 or claim 8 comprising means for detecting the position of the joint relative to the sleeve.

11. An apparatus according to any one of claims 8 to 10 wherein said sealant supplying means has a single duct through the sleeve.

12. An apparatus according to any one of claims 8 to 11 including means for sensing the orientation of the sleeve within the pipe, and means for rotating the sleeve.

13. An apparatus according to any one of claims 8 to 12 having an outlet in the sleeve for allowing gas to pass through the sleeve from the external surface of the sleeve.

14. An apparatus according to any one of claims 8 to 13, wherein the sealing means are inflatable members attached to the ends of the sleeves.

15. An apparatus according to any one of claims 8 to 13, wherein the sealing means are formed by the flexible walls attached to the ends of the sleeve such that the walls and sleeve form a single inflatable bladder.

16. An apparatus according to any one of claims 8 to 15, including, duct passing Uhrouh the sleeve to alLoz passage of gas along the pipe when the ends of the sleeve are sealed to the inside surface of the pipe.

17. An apparatus for sealing a joint in a pipe substantially as herein described with reference to and as illustrated in the accompanying drawings.