GB2132309A

GB2132309A - Plugging pipes

Info

Publication number: GB2132309A
Application number: GB8332741A
Authority: GB
Inventors: David William Prowse; John Richard Thorpe; Bryan Dawson
Original assignee: Roberts & Prowse Ltd
Current assignee: Roberts & Prowse Ltd
Priority date: 1982-12-10
Filing date: 1983-12-08
Publication date: 1984-07-04
Also published as: GB8332741D0; GB2132309B

Abstract

In plugging a pipe or pipe fitting in gas tight manner enabling the sealing of a branch tapping (26) in a main pipe (27) without disrupting gas flow in the main pipe, a hole is drilled in gas tight manner through the wall of the branch pipe (26) such that the through axis of the hole is oblique with respect to the longitudinal axis of the pipe at the point of drilling. An expandable bung (16) is located in the entrance of the branch pipe to the main pipe via the hole under gas tight conditions, and is expandable to form a gas tight seal at the pipe entrance prior to severing the branch pipe. <IMAGE>

Description

SPECIFICATION Method and apparatus for plugging pipes The present invention relates to a method of plugging a pipe or pipe fitting under gas tight conditions and to apparatus for use in the drilling and plugging of pipes under such conditions.

Many gas services employ branch pipes which connect directly into a main service pipe by means of, for example, a tapping in the main pipe. In many cases, the branch pipe has an elbow or bend which screws directly into a tapping provided on top of the main pipe. The removal of branch service pipes, as is required from time to time, while maintaining the gas supply of the main gas pipe, can be a complicated, expensive and hazardous exercise.

In one such method, five excavations are made along a main gas pipe, the central one of which being at the location of the branch pipe to be removed. At each of the pair of outermost excavations, a wall strengthening plate is welded to the main pipe and a bore is drilled under gas# tight conditions perpendicular to the pipe through both the plate and the pipe wall. A bypass pipe is then connected between these bores. At each of the pair of adjacent excavations a hole is then drilled through which rubber bags are introduced and expanded to seal the cross-section of the main pipe. Thereafter, the branch pipe is severed and extracted from its tapping in the main pipe and this tapping is sealed. The rubber diaphragms are then removed and their entry holes plugged, followed by the bypass line after its ports in the main pipe have been sealed.This procedure sometimes takes many days to complete and causes much expense and disruption, for example, to traffic. Further, the rubber diaphragms are liable to leak or become perforated through contact with jagged surfaces of the pipe at the entry holes created for them, leading to gas leakage and possible explosion. Further in medium gas pressure services, it is often necessary to use two pairs of such diaphragms to reduce the possibility of leakage, thereby necessitating additional work and expense.

In another method presently employed, a hole is drilled perpendicular to a straight portion of a branch pipe and expanding foam is pumped into the pipe through this hole. On setting, the foam seals the pipe which can be severed downstream of the sealing point and permanently capped. This method has the disadvantage that it can only be used on low pressure services and leaves a portion of the branch pipe permanently protruding from the main pipe. This provides a hazard for any future excavation work since such an unsupported pipe end portion can easily be snapped off by an excavator or even a hand pick axe and, result in gas leakage from the main pipe.

Up till now, it has not been possible to drill an oblique hole through the wall of a pipe or pipe fitting in a gas tight manner.

An object of the present invention is to provide a method of and apparatus for plugging a pipe or pipe fitting. An object of a preferred embodiment is to provide a method and apparatus enabling the sealing of a branch tapping in a main pipe without disrupting gas flow in the main pipe.

Another object of the present invention is to provide a jig enabling oblique drilling of the wall of a pipe or a pipe fitting, and, optionally also, the plugging of that pipe, under gas tight conditions.

According to the present invention there is provided a method of plugging a pipe or pipe fitting, the method comprising drilling a hole in gas tight manner through the wall of the pipe or pipe fitting, the through axis of the hole being oblique with respect to the longitudinal axis of the pipe or pipe fitting at the point of drilling, and introducing an expandable bung in gas tight manner through said hole for expansion in the bore of the pipe or pipe fitting to form a gas tight seal therein.

According to a further aspect of the present invention, there is provided a method of plugging a pipe or pipe fitting, the method comprising drilling a hole in a gas tight manner through the wall of the pipe or pipe fitting, the through axis of the hole being oblique with respect to the longitudinal axis of the pipe or pipe fitting at the point of drilling; introducing an expandable bung through said hole in gas tight manner and locating and expanding said bung in the bore of the pipe or pipe fitting to provide a gas tight seal in said pipe or pipe fitting.

According to a still further aspect of the present invention, there is provided a method of plugging a branch tapping of a main gas pipe, the method comprising drilling a hole in a gas tight manner through the wall of the branch pipe, the through axis of the hole being oblique with respect to the longitudinal axis of the pipe at the point of drilling; introducing an expandable bung through said hole in a gas tight manner and locating and expanding said bung in the entrance of the branch pipe to said main pipe to provide a gas tight seal at said entrance, and severing said branch pipe adjacent the bung.

According to the present invention there is also provided a jig for use in drilling and plugging a pipe or pipe fitting under gas tight conditions, said jig comprising a guide sleeve for receiving an axially arranged shaft, a mounting plate attached to and surrounding an orifice at one end of said guide sleeve, which mounting plate extends obliquely with respect to the longitudinal axis of said sleeve and is adapted to the shape of the pipe or pipe fitting, a sealing member located on said mounting plate and surrounding said orifice for making gas tight contact with the surface of said pipe, clamping means for clamping said mounting plate to the pipe and a valve located at the other end of said sleeve for gas tight sealing said sleeve, the bore of the valve being coaxial with that of the sleeve and that end of the valve bore remote from the sleeve being adapted to receive a collar for mounting an axially movable tool/plug carrying shaft in a gas tight manner.

One embodiment of the present invention further comprises a removable collar which is adapted for mounting coaxially with the valve bore. This collar has an axially arranged inlet port for receiving the axially movable shaft and provided with a gas tight O-ring seal. The length of the collar is sufficient to contain a tool/plug attached to the end of the shaft while the collar is mounted/dismounted, during which time the valve is closed.

Another embodiment of the present invention comprises an axially arranged drilling shaft. This shaft has a drill bit at one end and a guide member located behind this bit which is adapted to cooperate with the guide sleeve to support axial movement of the bit throughout drilling. In this embodiment, a feed screw is mounted on a frame on the collar and co-operates with a bearing on that end of the shaft remote from the bit. This frame is preferably mounted to the collar so that it may be rotated out of line with the collar inlet port, when not in use.

In a further embodiment for use in plugging pipes, the shaft comprises a sleeve member through which a co-axial rod extends. The sleeve member is adapted to carry removably an expandable bung, and the rod is adapted to cause expansion of this bung. The bung preferably comprises a compression expansion member through which a screw extends axially into a screw hole in a compression plate. The head of the screw and the rod of the shaft are adapted to cooperate such that rotation of the rod causes the compression plate to screw onto the expansion member. A sealing member is located at the head of the screw to prevent leakage of gas along the surface of the screw shaft. The bung and sleeve member are preferably provided with a bayonet fitting allowing detachment of the bung from the shaft after its location and expansion within a pipe.

In a further embodiment, at least an end portion of the sleeve member and rod is flexible to allow insertion of a bung in the bore of a pipe whose axis does not, at any point, coincide with that of the hole drilled through the wall of that pipe.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Flg. 1 illustrates, partially in section, an embodiment of the jig according to the present invention, mounted on the bend of a branch pipe; Fig. 2 shows a bung insertion device of the embodiment of the present invention; Fig. 3 shows, in longitudinal section, the bung shown in Fig. 2; Figs. 4A to 4D illustrate successive steps of an embodiment of the method according to the present invention; and Fig. 5 illustrates a stud extractor for use in an embodiment of the method of the present invention.

Figure 1 shows an embodiment of a jig, set up for gas tight drilling at the bend of a branch pipe.

The jig 1 comprises a guide sleeve 2 and a collar 3 which are connected in axial alignment by a valve 4. The guide sleeve 2 is composed of hardened steel and has a mounting plate 5 at its free end.

This mounting plate 5 extends in a plane oblique with respect to the axis of the sleeve 2, and is adapted to the shape of the pipe to which is to be mounted. A rubber seal 6 of for example, a silicone rubber adhesive, is provided on the base of the mounting plate surrouding the exist from the guide sleeve 5. This seal 6 provides a gas tight joint between the mounting plate 5 and the pipe surface when the plate 5 is clamped to the pipe by, for example, a pair of U-shaped clamps.

The collar member 3 is screw tapped into the valve 4 and is therefore removable. A drilling shaft 7 passes through an axially aligned port 8 in the collar 3. This port 8 is provided with an O-ring seal which allows the shaft to move axially without any leakage of gas.

The shaft 7 has a multi-flute cutter 9 at its working end. A cylindrical guide member 10 is provided on the shaft 7 behind the cutter 9. This guide member 10 is of such dimensions and is so positioned on the shaft as to prevent deflection of the cutter throughout drilling, to produce a symmetrical hole in the wall of the pipe.

The length of the collar 3 is such as to accommodate both the guide member 10 and the cutter 9 in a retracted position of the shaft 7 with the valve 4 closed, during dismounting of this collar.

A drill feed screw 11 is mounted coaxially with the shaft 7 on the collar 3 by means of a U-shaped frame 12. This frame 12 is pivotally mounted to the collar 3 so that it may be rotated out of the plane of the longitudinal axis of the jig, when not in use, e.g. during mounting and dismounting of the collar. The feed screw 1 1 co-operates with a bearing 13 provided on the end of the shaft 7.

Figure 2 shows a bung insertion shaft 17 provided for mounting axially within the jig 1 in a similar manner to the drilling shaft 7, but with the mounting frame 12 pivoted out of the axial plane of the jig. This shaft 1 7 comprises a rod 14 and coaxial sleeve member 15. A bung member 16 is removably connected to one end of the sleeve 1 5 by means of a bayonet fitting 18 comprising a peg 1 8a and slot 1 8b respectively located on the sleeve and bung. At the other end of the shaft 17, the rod 14 is provided with a handle 19. The length of the bung 16 is such as will allow its accommodation within the collar 3 when the shaft 17 is in the retracted position and the valve 4 is closed.

Figure 3 shows a cross-section through the expandable bung 16. This bung 16 comprises an annular expansion member 20 composed of, for example, rubber, through which a tension screw 21 extends and is received in a threaded hole in a compression plate 22. At the opposite end of the expansion member 20, the screw 21 passes through a hole in the base of a socket member 23, the head of the screw bearing against the surface of this base. The socket member 23 is provided to receive an end portion of the sleeve member 1 5.

The slot 1 8b of the bayonet fitting 1 8 is provided in the wall of this socket 23. A gas tight joint ring 24 is provided on the base of the socket 23 surrounding the head of the screw 21 to prevent gas leakage via the bore of the expansion member 20 to the outside. The head of the screw is provided with an hexagonal shaped recess 25 which receives a similarly shaped key provided on the end of the rod 14. Rotation of the rod handle 19 causes the screw to turn and the compression plate 22 to move along the shaft of the screw, thereby compressing the expansion member 20 and causing its diameter to increase.

An embodiment of the method according to the invention for plugging a main pipe tapping will now be described with reference to Figures 4A to 4D in which a branch pipe 26 is shown having a screw threaded bend located in the tapping of a main pipe 27.

After excavating to expose the branch pipe 26 at its junction with the main pipe 27, the surface of this pipe is cleaned and a jig according to the present invention having a suitably shaped mounting plate 12 for that branch pipe is located on its surface so that the axis of the jig coincides with that of the tapping in the main pipe 27 (see Figure 4A). The mounting plate is then clamped in position by means of clamps 28.

Standard pressure equipment is connected to the valve 4 of the jig 1 and pressure tests are carried out in order to ensure that the jig forms a gas tight seal with the pipe surface to be drilled.

The test pressure employed is normally set at least one and a half times the working pressure of the main service pipe 27. The pressure testing equipment is then removed.

The collar 3 with drilling cutter shaft 7 inserted, is then attached to the valve 4, the cutter 9 and guide member 10 entering the guide sleeve 2 and the drill feed screw 11 is located in position on the bearing 13 of the shaft 7. An oblique hole is drilled through the wall of the pipe bend using a ratchet handle on the drill feed screw, and drilling is continued until the drill cutter 9 has completely passed into the pipe bend.

The drill feed screw 11 and mounting frame 12 are then pivoted out of the axial plane of the drilling shaft and the cutter 9 and guide-member 10 are withdrawn into the collar 3. The valve 4 is then closed and the collar is removed from the valve (Figure 4B). The bung insertion shaft 17 bearing a bung 16 is then located in the port 8 of the collar 3 and the collar 3 attached to the valve 4 with the bung 16 located in the collar. The valve 4 is then opened to allow entry of the bung 1 6 into the pipe via the guide sleeve 2. The bung 16 is positioned in the entrance of the branch pipe where it enters the main service pipe in the region of the tapping and the rod handle 1 9 is rotated which, as already described, causes the expansion member 20 to increase in diameter and completely fill and seal the branch pipe.The sleeve member 15 is then detached from the bung 16 by applying longitudinal pressure while twisting the sleeve and is removed from the branch pipe together with the rod 14.

The jig may then be completely removed (Fig.

4C) and the branch pipe cut off between the bung 16 and the elbow band, generally approximately 25 mm above the main pipe (Fig. 4D).

A standard "Wask" tee set is then fixed in position directly over the branch pipe stub and centralized using a jig plate. A stud extractor tool which has been specifically adapted to fit the tee set, is inserted in the open bore of the pipe stub to engage its wall and the pipe stub is then removed from the main pipe tapping, under gas tight conditions.

Figure 5 shows such a pipe stud extractor 29 comprising a stud extractor tool 30 mounted on a shaft 31 having a drive square bearing 32 at its other end. A collar 33 is provided on the shaft directly behind the stud extractor tool 30 to prevent the extractor being blown out of the "Wask" tee set under the pipe pressure.

A permanent plug is then fitted in the tapped hole left in the main pipe using standard equipment and is pressure tested, anti-corrosion wrapped and back filled in known manner.

In a further embodiment of the method according to the present invention, a jig according to the present invention having a suitably shaped mounting plate is mounted on a straight branch pipe neighbouring the tapping in the main pipe. In this case, the longitudinal axis of the jig is arranged obliquely, not only with respect to the axis of the branch pipe at the point of drilling but also with respect to that of the tapping. After drilling the oblique hole through the branch pipe, in cases where the angle between the longitudinal axes of the pipe and jig is relatively small, which includes, for example, angles up to at least 1 50, the bung 1 6 may be inserted by means of a bung insertion shaft already described. Alternatively, the insertion shaft may have a flexible portion behind the plug to allow the plug to move into an axially aligned position in the branch pipe, on abutting the pipe wall opposite the hole.

The present invention may be used in connection with both low and medium pressure services and tests have shown that it can be used successively with gas services under pressures of up to at least 100 psi.

Claims

1. A method of plugging a pipe or pipe fitting, the method comprising drilling a hole in gas tight manner through the wall of the pipe or pipe fitting, the through axis of the hole being oblique with respect to the longitudinal axis of the pipe or pipe fitting at the point of drilling, and introducing an expandable bung in gas tight manner through said hole for expansion in the bore of the pipe or pipe fitting to form a gas tight seal therein.

2. A method of plugging a pipe or pipe fitting, the method comprising drilling a hole in gas tight manner through the wall of the pipe or pipe fitting, the through axis of the hole being oblique with respect to the longitudinal axis of the pipe or pipe fitting at the point of drilling; introducing an expandable bung through said hole in a gas tight manner and locating and expanding said bung in the bore of the pipe or pipe fitting to provide a gas tight seal in said pipe or pipe fitting.

3. A method as claimed in claim 1 or 2 wherein, after expansion of said bung, said pipe or pipe fitting is severed upstream of said bung.

4. A method of plugging a branch tapping in a main gas pipe, the method comprising drilling a hole in a gas tight manner through the wall of the branch pipe, the through axis of the hole being oblique with respect to the longitudinal axis of the pipe at the point of drilling; introducing an expandable bung through said hole in a gas tight manner and locating and expanding said bung in the entrance of the branch pipe to said main pipe to provide a gas tight seal at said entrance, and severing said branch pipe adjacent the bung.

5. A method as claimed in claim 3 or 4 wherein subsequent to severing said pipe or pipe fitting, said bung is replaced by a permanent plug under gas tight conditions.

6. A method as claimed in any preceding claim wherein a jig comprising a guide sleeve having an obliquely extending mounting plate surrounding one end and a valve at the other is employed in drilling said hole and introducing said bung into said bore in gas tight manner.

7. A method as claimed in claim 6 when dependent on claim 4 wherein said jig is mounted on said branch pipe such that the guide sleeve is substantially co-axial with said entrance to the main pipe.

8. A method as claimed in claim 6 or claim 7 wherein prior to drilling said pipe or pipe fitting, the gas tightness of the contact between the jig mounting plate and the surface of the pipe or pipe fitting is tested.

9. A method as claimed in any of claims 6 to 8 wherein a drilling shaft which is movably received in gas tight manner in a collar, is mounted to said jig by means of said collar and is inserted through the open valve into the sleeve for drilling.

10. A method according to claim 9 wherein after drilling said hole, the drilling shaft is withdrawn from said sleeve; the valve is then closed; the drilling shaft is replaced in said collar by a bung insertion shaft carrying the bung, and after opening said valve, this shaft and bung are inserted into said bore via said sleeve.

11. A method as claimed in claim 10 wherein said expansion of the bung is achieved by rotation of a portion of said bung insertion shaft.

12. A method according to any preceding claim wherein said bung comprises a resilient member which on longitudinal compression expands in the radial direction thereof.

13. A method of plugging a pipe or pipe fitting substantially as herein described with reference to Figures 4a to 4c with or without reference to any of Figures 1 to 3 and 5 of the accompanying drawings.

14. A jig for use in drilling and plugging a pipe or pipe fitting under gas tight conditions, said jig comprising a guide sleeve for receiving an axially arranged shaft, a mounting plate attached to and surrounding an orifice at one end of said guide sleeve, which mounting plate extends obliquely with respect to the longitudinal axis of said sleeve and is adapted to the shape of the pipe or pipe fitting, a sealing member located on said mounting plate and surrounding said orifice for making gas tight contact with the surface of said pipe, clamping means for clamping said mounting plate to the pipe and a valve located at the other end of said sleeve for gas tight sealing said sleeve, the bore of the valve being coaxial with that of the sleeve and that end of the valve bore remote from the sleeve being adapted to receive a collar for mounting an axially movable tool plug carrying shaft in a gas tight manner for drilling/insertion of an expandable bung in the pipe or pipe fitting.

1 5. A jig as claimed in claim 14 further comprising a removable collar which is adapted for mounting coaxially with the valve bore, said collar having an axially arranged inlet port adapted to receive the axially movable shaft in a gas tight manner.

16. A jig as claimed in claim 15 further comprising a feed screw mounted in a frame on the collar, which screw is adapted to co-operate with a bearing on that end of the drill shaft remote from the bit.

17. A jig as claimed in claim 1 6 wherein the frame is rotatably mounted to the collar so as to allow the frame to be rotated out of line with the collar inlet port.

18. An apparatus for plugging a pipe or pipe fitting under gas tight conditions, said apparatus comprising a guide sleeve for receiving an axially arranged shaft, a mounting plate attached to and surrounding an orifice at one end of said guide sleeve, which mounting plate extends obliquely with respect to the longitudinal axis of said sleeve and is adapted to the shape of the pipe or pipe fitting, a sealing member located on said mounting plate and surrouding said orifice for making gas tight contact with the surface of said pipe, clamping means for clamping said mounting plate to the pipe, a valve located at the other end of said sleeve for gas tight sealing said sleeve, the bore of the valve being coaxial with that of the sleeve and means at that end of the valve bore remote from the sleeve, adapted for mounting an axially movable tool plug carrying shaft to the apparatus in a gas tight manner for drilling/insertion of an expandable bung in the pipe or pipe fitting.

19. An apparatus as claimed in claim 18 wherein said means comprise a removable collar which is adapted for mounting coaxially with the valve bore, said collar having an axially arranged inlet port adapted to receive the axially movable shaft in a gas tight manner.

20. An apparatus as claimed in claim 19 further comprising a feed screw mounted in a frame on the collar, which screw is adapted to co-operate with a bearing on that end of the drill shaft remote from the bit.

21. An apparatus as claimed in claim 20 wherein the frame is rotatably mounted to the collar so as to allow the frame to be rotated out of line with the collar inlet port.

22. An apparatus as claimed in claim 18, further comprising an axially arranged drilling shaft having a drill bit at one end and a guide member located behind said bit which is adapted to co-operate with the guide sleeve to support axial movement of the bit throughout drilling.

23. An apparatus as claimed in claim 22, further comprising an axially arranged shaft for inserting the expandable bung in the pipe or pipe fitting, which comprises a sleeve member and a co-axially extending rod.

24. An apparatus as claimed in claim 23 wherein said sleeve member is adapted for releasable attachment to the bung.

25. An apparatus as claimed in claim 23 or 24 further comprising said bung which comprises an annular compression expansion member, and a threaded shaft which has a flange at one end and which extends axially through said member into a correspondingly threaded hole in a compression plate, said threaded shaft and said rod being adapted to co-operate such that rotation of the rod causes compression and hence radial expansion of the expansion member.

26. An apparatus as claimed in claim 25, wherein a sealing member is located at the flange of the threaded shaft to prevent leakage of gas along the surface of this shaft.

27. An apparatus for plugging a pipe or pipe fitting substantially as herein described with reference to Figures 1 to 3 of the accompanying drawings.

28. A bung for plugging pipes and pipe fittings which comprises an annular compression expansion member; a threaded shaft which has a flange at one end and which extends axially through said member into a correspondingly threaded hole in a compression plate and means for releasably attaching said bung to the end of a shaft, and in which expansion of said member is accomplished by advancing the threaded shaft through said hole.

29. A bung according to claim 28, further comprising a sealing member located at the flange of the threaded shaft for preventing leakage of gas along the surface of the threaded shaft.

30. A bung for plugging a pipe or pipe fitting substantially as herein described with reference to Figure 3 of the accompanying drawings.