GB2137718A

GB2137718A - Flow-stopping system

Info

Publication number: GB2137718A
Application number: GB08407693A
Authority: GB
Inventors: Hugh Eric Mceachran
Original assignee: BRAE TRADING Co Ltd
Current assignee: BRAE TRADING Co Ltd
Priority date: 1983-03-26
Filing date: 1984-03-26
Publication date: 1984-10-10
Also published as: GB8407693D0; GB2137718B

Abstract

The present invention provides a bag tube system incorporating a telescopically mounted support tube 18 of adequate length fully to support inflatable bags 28 in a wide range of pipe sizes for use in a flow-stopping system for a live gas pipe 2. The system comprises a valve means 4 securable to the gas pipe, and having a coupling means 10 for connection of a canopy 11 which is provided with a vent valve 12 and opening 14 for supporting a reciprocably displacable casing tube 15 towards and away from an opening 7 in said gas pipe, a support tube 18 telescopically mounted inside said casing tube 15 for displacement between a retracted position in which its distal end is clear of the valve means 4 and an extended position (Figs. 2, 3) in engagement with or proximity to the interior of the pipe 2 opposite said opening 7, and a bag inflation tube 23 telescopically mounted inside said support tube 18 with a bag coupling means 24 at one end and a pressurized fluid supply connection means 27 at its other end. The support tube 18 has an opening 20 at its distal end for receiving therethrough, in use of the system, an inflatable bag 28 connected to said inflation tube 23 via said bag coupling means 24, said bag 28 being retractable into the interior of said support tube 18. <IMAGE>

Description

SPECIFICATION Flow-stopping system This invention relates to a fluid pipe flowstopping system using inflatable bags.

It is often necessary temporarily to interrupt the flow of pressurized gas in a 'live' gas main in a particular section in order for example to insert a new fitting or renew a short section of the pipe without shutting down the whole main and without escape of gas to the atmosphere.

Conventionally this is effected by inserting by means of bag tubes mounted on gate valves, 2 inflatable gas bags at each side of the section via respective small holes drilled through the wall of the pipe and inflating the bags to fill the whole cross-sectional area of the pipe thereby to seal the pipe at that point. Known systems use a relatively large form of construction with a special canopy and a range of different sized support shoes for each of the different sizes of pipes to be sealed, in order to support the bag against axial movement inside the pipe. It is an object of the present invention to provide a flow-stopping system of relatively simple and economic construction.

The present invention provides an improved bag tube system incorporating a telescopically mounted support tube of adequate length fully to support bags in a wide range of pipe sizes for use in a flow-stopping system suitable for use in a live gas pipe which system comprises a valve means having a releasable clamping means for releasably securing the valve means to the gas pipe, said valve means having a coupling means for connection to said valve means of a canopy which is provided with a vent valve for use in purging and/or venting of the interior of the gas pipe and a casing tube opening for supporting a casing tube reciprocably displacable through said casing tube opening towards and away from the gas pipe opening, seal means being provided between said casing tube and casing tube opening, a support tube telescopically mounted inside said casing tube for displacement between a retracted position in which its distal end is clear of the valve means and an extended position in engagement, with or proximity to, in use of the system, the interior of said gas pipe opposite said gas pipe opening and a bag inflation tube telescopically mounted inside said support tube having a bag coupling means at one end and a pressurised fluid supply connection at its other end remote front said casing tube, further respective sealing means being provided between said relatively axially displaceable casing tube and bag inflation tube, said support tube having at its distal end an opening through which an inflatable #bag connected, in use, to said bag inflation tube via said bag coupling means and temporarily located within said support tube may be urged, by axial movement of said bag inflation tube out of said support tube, into said gas pipe, and retracted fully back into said support tube.

By means of the present invention various sizes of pipe can be readily stopped off with a single size of bag tube by virtue of the telescopic construction of the casing and support tubes permitting on the one hand full retraction thereof and on the other full extension of the support tube across the pipe from the opening in the wall thereof to provide axial support for the inflated bag and maintenance of flow stopping. Moreover this can be achieved with the use of a substantially standard form of canopy such as that used for mounting fittings to the gas pipe without the need for especially large canopies.

The mode of operation of the system and further preferred features of the invention will appear from the following detailed description given by way of example of a preferred embodiment of a flow stopping system illustrated with reference to the accompanying drawings in which: Fig. 1 is a partly schematic sectional elevation through a flow-stopping system of the invention in use prior to insertion of the gas bag into the pipe; Fig. 2 is a corresponding view with the bag partly inserted; and Fig. 3 is a corresponding view with the bag inflated to seal the pipe.

Fig. 1 shows a flow-stopping system 1 of the invention mounted on a gas main pipe 2 through which the gas flow is as indicated by the arrow 3.

A gate valve means 4 comprising a body 5 and valve member 6 is releasably secured to the pipe 2, at an opening 7 drilled in the pipe, in conventional manner with the aid of clamping means 8~the valve means 4 being then used to close off the opening 7 from the atmosphere 9.

The valve means 4 has a gas-tight coupling means 10 via which a substantially standard form generally bell-shaped fittings canopy 11 is mounted with its mouth 12 above the opening 7.

At one side the canopy 11 is provided with a vent valve 12 a, such a part being readily and economically incorporated in a standard fittings canopy.

At its upper end 13 remote from its mouth 12, the canopy has a reduced diameter casing tube opening 14 through which extends a casing tube 15 supported in said opening 14 for reciprocal displacement therethrough. At its lower end 16 the casing tube 15 has a collar 17 which retains the casing tube 15 against withdrawal from the canopy 1 1 and also can act as a support for the casing tube against the outside of the pipe 2 around the pipe opening 7. Inside the casing tube 15 is telescopically mounted with a sliding fit a support tube 18. At its distal end 19 the support tube 18 has a side opening 20 below and opposite which is provided a plug 21 having an inclined face 22.

Inside the support tube 18 is telescopically mounted a bag inflation tube 23 with a bag coupling means in the form of a screw-threaded portion 24 at its lower end 25 inside the support tube and at its upper end 26 which projects from the upper end of the support tube 18, a pressurized fluid supply connection means 27. An inflatable gas bag 28, for example, an inner rubber bag inside an outer polyamide fabric bag is connected by means of a female screw-threaded connector 28a to the lower screw-threaded end 25 of the inflation tube 23. In order to provide the bag 28 with sufficient stiffness to allow it to be urged out of the support tube 18 into the gas main pipe 2, the bag desirably contains a flexible semirigid arcuate member 28b which may be a plastics tube extending from one end to another of the bag and provided with apertures in its side wall via which the bag can be inflated.Further details of suitable bag construction are provided in Patent Specification No. GB.A-1 245-254. In Fig. 1 the inflation tube 23 is shown fully retracted with the gas bag 28 retracted inside the support tube 18.

The latter as well as the casing tube 15 are also substantially fully retracted and thus well clear of the gate valve member 6. The gate valve member 6 may now be opened and the casing tube 15 pushed down as far as possible so that the collar 17 abuts the pipe 2 at the opening 7. The inflation tube 23 can now be pushed down to urge the bag 28 toward the opening 2 in the supporting tube 1 8 and simultaneously the distal end 19 of the support tube 18 into abutment with the inside of the pipe 2 opposite the opening 7 the bag 28 being deflected off the inclined face 22 of the plug 21 to extend generally along the pipe 2.The bag 28 may now be inflated using a pressurized gas supply connected to the inflation tube 23 via the connection means 27 to a predetermined pressure at which it fully fills the pipe interior for a given length thereby sealing it against passage of gas therethrough.

In order to ensure correct attitude of the opening 20 of the support tube 18 within the pipe a guide pin 29 is provided inside the casing tube for engagement with a longitudinally extending guide slot 30 in the outer wall of the support tube and suitable index marks 31, 32 are provided respectively on the outside of the casing tube 15 and the outside periphery of a washer 33, rotatable on a screw-threaded portion of the inflation tube 23 so that correct support tube and bag orientation may be obtained by simple alignment of those marks 31, 32. The desired orientation of the washer on the tube is secured with the aid of a concentric helical spring 34.

A grub screw 35 is provided in a radial screwthreaded bore in the collar 17 such that it may be screwed in to engage the screw-threaded connector 28a of the bag 28 in order to secure the bag against rotation when tightening the inflation tube 23 into the screw-threaded connector 28a.

In other respects, the construction and mode of use of the above described system is generally similar to conventional systems. It is however possible to service a range of different gas pipe sizes e.g. 2 inch (50 mm) to 6 inch (1 50 mm) in a simple and economic manner with regard both to the costs of the system and its mode of operation.

Various modifications may be made to the above described embodiments without departing from the scope of the present invention. Thus for example the guide slot 30 could be replaced by a guide channel in order to avoid any possibility of interference between the guide pin 29 and the bag 28. Thus with a bag tube system of the present invention it is no longer necessary to carry a large stock of different sizes of begs and support shoes and possibly even other pans, either on the part of the manufacturer or user. Moreover the need to change the support shoe for every different pipe size encountered is eliminated.

Claims

1. An improved bag tube system incorporating a telescopically mounted support tube (18) of adequate length fully to support bags (23) in a wide range of pipe sizes for use in a flow-stopping system suitable for use in a live gas pipe (2) which system comprises a valve means (4) having a releasable clamping means (8) for releasably securing the valve means to the gas pipe, said valve means having a coupling means 110) for connection to said valve means of a canopy (11) provide with a vent valve (12) for use in purging and/or venting of the interior of the gas pipe (2) and a casing tube opening for supporting a casing tube (15) reciprocably displacable through said casing tube opening towards and away from the gas pipe opening (7) seal means being provided between said casing tube and casing tube opening, a support tube (1 8) telescopically mounted inside said casing tube (15)for displacement between a retracted position in which its distal end is clear of the valve means (4) and an extended position in engagement with or proximity to the interior of said gas pipe (2) opposite said gas pipe opening (3) and a bag inflation tube (23) telescopically mounted inside said support tube (18) having a bag coupling means (24) at one end and a pressurized fluid supply connnection at its other end remote from said casing tube (15), further respective sealing means being provided between said relatively axially displaceable casing tube (1 5) and bag inflation tube (23), said support tube (1 8) having at its distal end an opening (20) through which an inflatable bag (28) connected, in use, to said bag inflation tube (23) via the said bag coupling means (24) and temporarily located within said support tube (18), may be urged by axial movement of said inflation tube (23) out of said support tube (1 8), into said gas pipe (2), and retracted fully back into said support tube (18).

2. A bag tube system according to claim 1 wherein said support tube opening (20) is on one side of the support tube 18 below and opposite which opening (20) is provided an inclined face (22) facing towards said opening (20) and the interior of the support tube (1 8) for deflecting, in use, a said inflatable bag (28) when said inflation tube (23) is advanced axially tuwards the distal end of said support tube (18).

3. A bag tube system according to claim 1 or claim 2 wherein said inflation tube (23) is provided with a flange means at or in proximity to said bag coupling means (24) which flange means is a sliding fit inside said support tube (18) for radially supporting said inflation tube (23) in said support tube (18) and is engageable with a respective flange means at the proximal end of the support tube (1 8) for retraction thereof from the pipe (2) into said casing tube 15 upon retraction of the inflation tube (23).

4. A bag tube system according to any one of claims 1 to 3 wherein said casing tube (15) and support tube (18) are provided with radially extending interengaging guide means (29, 30) formed and arranged for maintaining the relative angular disposition of said casing and support tubes (15) and (18) whilst permitting relative axial movement therebetween.

5. A bag tube system according to claim 4 wherein the inflation tube (23) and support tube are provided with rotational index means for indicating, in use, the angular disposition of a bag (28) secured to the inflation tube (23) and the support tube opening (20) respectively, with respect to the longitudinal axis of the pipe (2) thereby to ensure a correct disposition of the bag (28) to the pipe (2) prior to insertion of the bag (28) into the pipe (2).

6. A bag tube system according to any one of claims 1 to 5 which includes a said inflatable bag (28) connected to said bag coupling means (24).

7. A bag tube system according to claim 6 wherein said bag (28) includes a resiliently deformable elongate arcuate support member extending from an inlet end of the bag (28) to its distal end.

8. A bag tube system according to claim 7 wherein said bag (28) comprises an inflatable elastic inner bag and a protective outer bag.