GB2420837A

GB2420837A - Inflatable pipe welding back shield device

Info

Publication number: GB2420837A
Application number: GB0426330A
Authority: GB
Inventors: Martyn James Smith
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-12-01
Filing date: 2004-12-01
Publication date: 2006-06-07
Anticipated expiration: 2024-12-01
Also published as: GB0426330D0; GB2420837B

Abstract

A device for establishing an environment of a required fluid inside a length of pipe, comprising two pipe engaging members adapted to engage the interior surface of the pipe at respective spaced positions therealong, and connections for introducing said fluid into the interior of the pipe between said engaging members, wherein each engaging member comprises a casing of annular configuration for contacting the pipe interior surface and containing a ring-like inflatable element, and wherein said engaging members are joined by a flexible sleeve portion adapted to constrain the fluid in an annular space defined between the engaging members, the sleeve, and the pipe interior surface. The device further comprises an opening for release of fluid from the annular space, the opening being provided with a material adapted to retard flow through it.

Description

Title: Device for blocking-off part of interior of a pipe scription of

Invention This invention relates to a device for the establishment and maintenance of an environment of a required fluid in the interior of a length of pipe, conduit or the like (the term "pipe" will be used generically herein).

For example, an atmosphere of inert gas such as argon might be required to be established in the interior of a length of pipe where two pipe elements are required to be joined to one another by welding circumferentially of the pipe. It is known that the required environment can be established and maintained inside a length of pipe by disposing two blocking members within the pipe, each blocking member including an inflatable bladder contained within a casing and arranged so that inflation of the bladder expands the casing until it is in firm contact with the inside surface of the pipe. When the two blocking members have been thus caused to engage and block the pipe, a region is defined between them in which the required atmosphere of inert gas can be established and maintained by introducing the inert gas between the blocking members at a rate corresponding to the rate at which it escapes through whatever openings might exist in the pipe.

A device operable in this manner is disclosed in my published patent application GB 2383 108A. As described in that application, each blocking member comprises a casing having a peripheral portion for engaging the pipe interior surface and containing a ring-like inflatable element, and a closure portion closing the space within the peripheral portion. The ring-like inflatable element conveniently is an irmer tube as used in vehicle tyres. Such a device performs satisfactorily, but if the pipe is of large diameter a large quantity of the inert gas is required firstly to purge air from the pipe interior between the blocking members and then to maintain the inert atmosphere therebetween while the welding is carried out. In addition to being wasteful of the inert gas, the purging process taking a substantial period of time, and the welding has to be delayed until the purging of air has been completed. It is broadly the object of the present invention to address this problem.

According to the present invention I provide a device for establishing an environment of a required fluid inside a length of pipe, comprising two pipe engaging members adapted to engage the interior surface of the pipe at respective spaced positions therealong, and means for introducing said fluid into the interior of the pipe between said engaging members, wherein each engaging member comprises a casing of annular configuration for contacting the pipe interior surface, and containing a ring-like inflatable element, and wherein said engaging members are joined by a sleeve portion of flexible material adapted to constrain the required fluid in an annular space defined between the engaging members, the sleeve, and the pipe interior surface.

Conveniently the sleeve is of about the same diameter as the inside diameter of the annular casings of the engaging members, which will be approximately the same as the nominal inside diameter of a normallyinflated one of the ring-like inflatable elements contained within the engaging members.

In a device in accordance with the invention, the provision of the sleeve joining engaging members of annular configuration means that the volume which has to be occupied by the inert gas or other required fluid within the pipe is much reduced as compared with the volume if the sleeve were not present and the entire space between blocking members had to be filled. Thus, the time taken to purge the pipe interior space of air, so that welding can take place, is much reduced, as is the quantity of inert gas required.

The casing of each engaging member may be of flexible substantially impermeable material such as polyurethane-coated woven fabric e.g. of nylon, as described in my patent application aforesaid, and the sleeve may be of the same or similar material. However, in the case of the sleeve, it must be protected against damage due to the carrying out of welding in the vicinity thereof, e.g. by making the sleeve of, or providing the sleeve with a covering of, a material resistant to heat, fumes, sparks, and molten metal splashes, which are likely to be encountered when welding is carried out in the vicinity. Such a material may comprise a glass fibre fabric for example.

The sleeve may be provided with means for releasing the fluid from the annular space defined between the sleeve and pipe. Such means may afford some resistance to the flow of fluid therethrough, so that the inert gas cannot escape too readily when the welding has been completed or substantially completed, whilst not allowing any, or any substantial, pressure to be built up in the annular space, which could cause problems. Conveniently the means for permitting the escape of the fluid from the annular space may comprise an element of sintered material held in an aperture in the sleeve.

The invention will now be described by way of example with reference to the accompanying drawing, which is a perspective view, partly broken away, of a device in accordance with the invention, in use within a pipe.

The drawing shows a length of pipe 10 which comprises two portions 11, 12 in end to end relationship joined by a circumferential weld 13 which is shown as being partly completed. In the interior of the pipe there are engaging members indicated generally at 14, 15, one in each of the pipe portions 11, 12 at a sufficient distance from the weld 13 so as not to suffer damage from the welding process.

The engaging members 14, 15 are of the same construction as one another and the engaging member 15 is shown as comprising an aimular casing 16 of toroidal configuration, in which is accommodated a ring-like inflatable element 17. The casing 16 is of a flexible fabric-based material e.g. a polyurethane-coated nylon fabric with appropriately shaped pieces thereof sewn together so as to be able to assume the toroidal configuration with its outer periphery pressed against the interior surface of the pipe when the element 17 is inflated. The element 17 is an inner-tube such as is used in vehicle tyres e.g. a motor scooter, motor cycle, car or truck according to the size of pipe with which the device is to be used. The engaging member 14 is of the same construction as the engaging member 15; as illustrated they are of the same nominal diameter as one another (bearing in mind that the fact that they are inflatable means that they are able to accommodate some small variations in inside diameter of the pipe with which they are intended to fit) although they could be of different nominal sizes from one another if they were intended to be used where a pipe increases or decreases in diameter.

The casings of the engaging members 14, 15 are joined by a sleeve 18 which is of the same or similar material as the casings of the engaging member, provided on its external surface facing the interior of the pipe with a suitable protective covering of a material resistant to the effects of heat and debris such as sparks and small drops of molten metal to which it is likely to be subjected when welding is being carried out in the vicinity.

A pipe 20 for supply of inert gas, e.g. argon, extends firstly to a Tpiece 21 within the end of the sleeve 18 inside the engaging member 14, and then on to further T-pieces 22, within the sleeve 18, and 23, within the engaging member 15. The T-piece 23 is connected to a further pipe 28 extending onwardly therebeyond, and ending at a pressure relief valve 29. The T-pieces 21, 23 provide connections 24, 25 respectively to the inflation stems of the inner-tubes within the engaging members 21, 23. The T-piece 22 provides a connection 26 which extends through the sleeve 18 and ends at a pressure relief valve 27.

The pressure release valve 27 is set to open at a pressure slightly greater than that required to inflate the inner tubes within the casings of the engaging members 14, 15 to cause the engaging members firmly to engage the internal surface of the pipe while further inflation of the inner tubes is constrained by the casings of the engaging members. The pressure release valve 29 is set to open at a greater pressure than that at which the valve 27 opens, to limit the maximum pressure which can be achieved within the engaging members so that they cannot be damaged by excessive pressure.

The sleeve 18 is provided, as indicated at 30, with an opening containing an element of sintered material (such as, for example, are used as silencers in compressed-air devices) which permits release of inner gas from the annular space between the sleeve and pipe, whilst providing a small degree of resistance to such escape.

Also shown in the drawings is that the engaging member 14 is provided with handling elements e.g. loops of rope or tape material as indicated at 31, e.g. at diametrically opposed positions. Similarly the engaging member 15 is provided with handling elements 32. These assist the positioning of the engaging members, when deflated, at the required places within a pipe.

In use of the device, it is placed inside the pipe 10 with the innertubes of the engaging members deflated, enabling the engaging members to be positioned as required to each side of the region where welding is to take place, then the required inert gas, e.g. argon, is supplied through the pipe 20 to inflate the inner-tubes and cause the engaging members firmly to engage the internal surface of the pipe. When this has been achieved and the inner-tubes can expand no further owing to being restrained by the casings of the engaging members, an increase in pressure of the supplied gas will cause the relief valve 27 to open and release gas into the annular space surrounding the sleeve 18 between the engaging members. After sufficient gas has been released into the annular space to purge air therefrom, welding can take place.

Prior to completion of the welding, most of the inert gas supplied to the annular space between the sleeve and pipe will escape through the gap between the faces which are to be welded. As welding progressively closes that escape route, more will escape through the opening 30 in the sleeve. The opening prevents uncontrolled rise in pressure in the annular space by permitting release of inert gas from the space to the atmosphere while the sintered element therein provides a small restriction to such release. Pressure release valve 29 prevents damage to the engaging members or any other part of the system from excess pressure.

After use, the supply of inert gas to the device is disconnected or turned off and the inner-tubes of the engaging members deflated. Then the device can simply be withdrawn axially from the interior of the pipe.

When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof

Claims

1. A device for establishing an environment of a required fluid inside a length of pipe, comprising two pipe engaging members adapted to engage the interior surface of the pipe at respective spaced positions therealong, and means for introducing said fluid into the interior of the pipe between said engaging members, wherein each engaging member comprises a casing of annular configuration for contacting the pipe interior surface and containing a ring-like inflatable element, and wherein said engaging members are joined by a sleeve portion of flexible material adapted to constrain the fluid in an annular space defined between the engaging members, the sleeve, and the pipe interior surface.

2. A device according to claim 1 wherein the sleeve is of generally the same diameter as the inside diameter of the annular casing of the engaging members, corresponding to the nominal inside diameter of a normally-inflated one of the inflatable elements.

3. A device according to claim 1 or claim 2 wherein the sleeve is of or has a covering of a material resistant to damage from welding performed in the vicinity thereof.

4. A device according to any one of the preceding claims wherein the sleeve is provided with means for release of fluid from the annular space.

5. A device according to claim 4 wherein the means for release of fluid comprises an opening having a means for retarding flow therethrough.

6. A device according to claim 5 wherein the means for retarding flow comprises an element of sintered material.

7. A device according to any one of the preceding claims wherein the inflatable elements comprise inner tubes as used in vehicle tyres.

8. A device substantially as hereinbefore described with reference to andlor as shown in the accompanying drawing.

9. Any novel feature or novel combination of features described herein and/or in the accompanying drawing.