More specifically, the invention relates to apparatus for insertion through a pre-drilled hole in a pipe wall for internally sealing the pipe upstream of the insertion hole.

Particularly, but not exclusively, the invention provides apparatus for stopping gas flow through a pressurised gas main.

It is often necessary to empty and seal a length of underground gas main so that work can be carried out on the main in safety. The use of inflatable bladders for stopping the flow of low pressure gas has been known for many years. A single bag cannot generally be relied upon to provide a safe and complete seal inside a gas pipe and thus it has become customary to use two separately inflated bags. In the most conventional arrangement two separate insertion holes must be drilled in the pipe to allow insertion of each bag, any gas present in the space between the bags then being vented to atmosphere through one of the bag insertion holes. Furthermore, it is often necessary to drill an extra hole upstream of the bags so that the pressure in the pipe at that point can be monitored. Consequently, with such conventional arrangements there will be at least two and possibly three spaced apart holes drilled in the pipe.

In contrast to the above conventional methods, European patent number 0 064 653 discloses a pipe sealing apparatus comprising two inflatable bags which are connected together and inserted through a single hole drilled in the pipe wall. Apart from the advantage of reducing the number of drilling operations required, this also greatly reduces the size of the excavation required to access the pipe. The ability to reduce the size of the excavation has become particularly important in recent times with the increasingly stringent demands of environmental protection and the highway authorities (under whose roads gas mains are typically laid). For instance, in the UK the material from the surface and substrate must be dug out and transported to an authorised tip for which a tax is levied based on weight of the material. New materials must then be brought to the site and the road surface must be restored to strict specification. With the apparatus disclosed in EP 0 064 653 the bags can be inserted into a buried section of pipe and the excavation can be kept relatively small (provided access is not required to the pipe upstream of the bags).

Although the apparatus disclosed in EP 0 064 653 is reliable and has the advantages mentioned, it is relatively complex and expensive. The expense is a significant disadvantage because the bags can become unserviceable due to mishandling, mechanical damage or ageing. Since the consequences of failure in use are potentially catastrophic the apparatus of EP 0 064 653 must be scrapped if either of the bags is damaged.

It is an object of the present invention to obviate or mitigate the above disadvantages.

According to the present invention, there is provided apparatus for insertion through a pre-drilled hole in a pipe wall for sealing the pipe internally upstream of said insertion hole, the apparatus comprising two spaced but connected inflatable assemblies mounted to a flexible guide member for insertion and disposition upstream of said insertion aperture, each inflatable assembly comprising an inflatable bladder mounted around a respective flexible support member the assemblies being connected by a connecting member such that in use one lies upstream of the other, wherein each of said support and connecting members is provided with coupling means for releasibly coupling the inflatable assemblies to the guide member and/or connecting member.

Thus, with the present invention either of the inflatable assemblies may be replaced without the need to replace the other inflatable assembly, or for that matter any other component of the apparatus.

Preferably the guide member and connecting member provide means for delivering pressurised air to each inflatable assembly to inflate the respective bladder.

For instance, the guide, connecting and support members may be flexible tubes which themselves house air supply pipes.

Preferred embodiments of the invention provide coupling means which, for instance, allow the two inflatable assemblies to have an identical construction. This means that manufacturing costs are reduced by reducing the number of different components. In addition, providing bags of identical construction ensures that in the difficult conditions that may be encountered on site there is no possibility of an attempt being made to connect the bag assemblies in the wrong order which would be a potential problem if the bag assemblies had different constructions. It would be possible to provide bag assemblies of different constructions which are nevertheless configured so that they cannot be connected incorrectly, for instance by making some of the couplings left-hand threaded and some right-hand threaded, but such distinctions might not be obvious to a non-engineer in such poor light, cold and wet muddy conditions that may be encountered on site, and would therefore not necessarily prevent an attempt being made to fit the bags incorrectly which could possibly damage the apparatus.

The apparatus also preferably includes means of monitoring the pressure within the pipe upstream of the apparatus. For instance, a pressure monitoring pipe may be provided which extends through the guide, connecting and support members.

Other preferred features of the invention are described below.

A specific embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawing.

The drawing is a schematic illustration of apparatus in accordance with one embodiment of the present invention installed in a gas mains pipe line through which gas normally flows from right to left as seen in the drawing. In particular, the drawing illustrates the apparatus fully installed in the pipe line following insertion through a hole drilled in the pipe wall. The hole, which would be to the left of the apparatus as seen in the drawing, is not illustrated. Neither is there any illustration or detailed description of suitable apparatus for drilling the hole and inserting the illustrated apparatus since such apparatus may be entirely conventional. For instance, the present applicants manufacture a universal drilling machine which meets appropriate British and European standards. The machinery comprises a universal base which is mounted and sealed with respect to the pipe and which may support, initially, drilling apparatus for drilling a hole and then subsequently bag insertion equipment which includes a canopy which is adapted to be mounted to the universal base.

Similarly, details of equipment which may be used to supply air to inflate the apparatus, to vent gas and to monitor pressure upstream of the apparatus, will not be described as appropriate equipment could readily be provided by the skilled person.

Rather, the following description is limited to details of the apparatus strictly in accordance with the invention which will enable the appropriately skilled person to implement the invention.

Referring to the drawing, the illustrated apparatus comprises a flexible (semi- rigid) guide tube 1 which is coupled to a downstream inflatable assembly 2 which is itself connected to an upstream inflatable assembly 3 via a connecting tube 4 which is coupled between the assemblies 2 and 3.

Each of the inflatable assemblies 2 and 3 comprises an inflatable bladder 5,6 mounted on a flexible support tube 7,8. Similarly, the connecting member 4 comprises a length of flexible tube 9. The guide tube 1, inflatable assemblies 5,6 and connecting member 4, are all interconnected by way of couplers fitted in the ends of respective tubes. Specifically, male coupler members 10,11,12 and 13 are fitted to the upstream ends of the guide tube 1, support tube 7, connecting tube 9 and support tube 8 respectively. Female coupler members 14,15 and 16 are fitted to the downstream ends of the support tube 7, connecting tube 9, and support tube 8 respectively. A further female coupler 17 is used to couple a blanking member 18 to the coupler 12 at the upstream end of the support tube 8 of the upstream inflatable assembly 3. The male coupler members 10,11,12 and 13 comprise a spigot portion which extends into the respective tube to which the coupler is fitted, and an externally screw threaded terminal flange which is received within a screw threaded socket provided by each of the female coupler members 14,15,16 and 17. The sockets 14a, 15a, 16a and 17a of the female coupler members are rotatable on spigot bodies which extend into respective tubes.

The provision of male and female couplers ensures that the inflatable assemblies 2,3 and the connecting member 4, are connected the right way around to ensure proper operation of the apparatus (for which see below). Furthermore, it will be seen that the coupling members of the two inflatable assemblies 2,3 are identical which enables either inflatable assembly 2,3 to be connected in the upstream or downstream position.

Guide tube 1 contains three smaller diameter pipes; a first air supply pipe 20, a second air supply pipe 21, and a pressure monitoring pipe 22. Each of these pipes extends into the coupler member 10. Coupler member 10 is also provided with a bore 23. A cross-section through the tube and coupler member 10 is shown as a scrap view to the drawing.

Each of the support tubes 7 and 8 of inflatable members 2 and 3 contains three identically arranged pipes; a first air supply pipe 24 which extends through the respective tube 7,8 for the supply of pressurised air to the respective bladder 5,6; a second air supply pipe 25 which extends through the respective support tube 7,8; and a pressure monitoring pipe 26 which also extends through the respective tube. The connecting tube 9 contains only two pipes, an air supply pipe 27 and a pressure monitoring pipe 28.

The various pipes extend between the couplers of the respective tubes 7,8 and 9 such that they match up with their counterparts in the following way. When the downstream inflatable assembly 2 is coupled to the guide tube 1, the first air pipe 24 communicates with the first air pipe 20 of the guide tube, the second air pipe 25 communicates with the second air pipe 21 of the guide tube, and the pressure monitoring pipe 26 communicates with the pressure monitoring pipe 22 of the guide tube. Where the connecting member 4 is coupled to the downstream inflatable assembly 2, the air pipe 27 communicates with the air pipe 25 and the pressure monitoring pipe 28 communicates with the pressure monitoring pipe 26. When the upstream inflatable assembly 6 is coupled to the connecting member 4, the first air supply pipe 24 communicates with the air pipe 27 of the coupling member and the pressure monitoring pipe 26 communicates with the pressure monitoring pipe 28 of the coupling member. In particular, it will be seen that the connecting member 4 connects the second air supply pipe of the downstream inflatable assembly 2 with the first air supply pipe of the upstream inflatable assembly 3. Furthermore, the male coupler member 12 of the connecting member 4 blanks off the downstream end of the air pipe 25 of the upstream inflatable assembly 3. Finally, the blanking member 18 contains only a single short pipe, i. e. a pressure monitoring pipe 28 which communicates with the pressure monitoring pipe 26 of the inflatable assembly 3.

Each coupler also contains a throughbore 23 corresponding to the throughbore 23 of the coupler 10 of guide member 1 described above. The throughbores of each coupler communicate with one another and with an aperture 29 provided in the connecting pipe 9.

The couplers may be suitably keyed to one another to ensure that the respective pipes and bores align with one another automatically when the couplers are coupled together.

In use, the first air pipe 20 of the guide member 1 together with the first air pipe 24 of the inflatable assembly 2 provides a channel for the supply of pressurised air to inflate the bladder 5. The air supply pipe 21 of guide member 1 together with the second air pipe 25 of inflatable assembly 2, the air pipe 27 of the connecting member 4 and the first air supply pipe 24 of the inflatable assembly 3, provide means for the supply of pressurised air to inflate the bladder 6. The pressure monitoring pipes 22,26,28 and 29, together form a pipe for feeding pressurised gas from upstream of the apparatus to a point external of the aperture through which the apparatus is installed to enable the upstream pressure to be monitored. Finally, the channel provided by the bores 23 provides a channel for venting gas (via the installation hole) from between the two inflatable assemblies 2 and 3.

To summarise, the apparatus according to the invention is designed to be inserted through a single installation hole drilled in the pipe wall and provides means for the independent inflation of the bladders 5 and 6, means for monitoring the pressure upstream of the apparatus, and means for venting gas from the space between the two inflatable assemblies. Moreover, this is achieved using components which are independently replaceable. For instance, if either bladder 5 or 6 becomes damaged then that particular inflatable assembly 2,3 can be replaced without the need to replace any other components of the apparatus.

In addition, the two inflatable assemblies are identical and so can be connected in either order, the correct orientation of connection being assured by the provision of male/female connectors, the disposition of the various air pipes (and in particular the air pipe of connecting member 4 which connects the second air pipe of one assembly to the first air pipe of another) provides for independent inflation of the bladders 5 and 6.

It will be appreciated that many modifications could be made to the details of the embodiment described above. For instance, the advantage of having readily separable components which can be individually replaced may be maintained in a system in which the upstream and downstream inflatable assemblies are not identical. The various air pipes and pressure monitoring pipes need not necessarily be disposed within a larger diameter tube which provides the means to support and guide the inflatable bladders. The particular arrangement illustrated does, however, provide for the design of relatively simple couplers. In addition, although advantageous it is not absolutely necessary that the inflatable assemblies 2 and 3 are identical. For example, each of the pairs of couplers 10 and 14,11 and 15,12 and 16, and 13 and 17 could have different mating configurations to ensure that inflatable assemblies that are not interchangeable are connected in the correct order.

Other possible modifications will be apparent to the appropriately skilled person.