WO2001031250A1

WO2001031250A1 - A plug fitting

Info

Publication number: WO2001031250A1
Application number: PCT/GB2000/003326
Authority: WO
Inventors: Andrew Welfare
Original assignee: Glynwed Pipe Systems Limited
Priority date: 1999-10-23
Filing date: 2000-08-31
Publication date: 2001-05-03
Also published as: AU6854800A; JP2003513210A; GB9925025D0

Abstract

A plug fitting for plugging an aperture defined by a wall comprises a body portion (1) for insertion into the aperture which in use anchors the fitting to the wall (10). A sealing member (3) is disposed around the body portion which has compression means (6) which in use compresses the sealing member (3) against the wall (10) around the aperture. A collar (2) surrounds the sealing member (12) and is fabricated from a weldable material which may be welded to the wall (10). The sealing member (3) is fabricated from a heat resistant material, such that in use the collar (2) may be welded to the wall (10) around aperture (16) to seal the fitting to the wall (10) without breaking the seal provided by the sealing member (3).

Description

A PLUG FITTING

The present invention relates to a fitting for plugging an aperture in a wall such as a wall of a fluid container, referred to hereinafter as a "plug fitting" Particularly, but not exclusively, the invention relates to a plug fitting for plugging a pre-dπlled hole in the wall of a pipe such as a gas mams pφe

Many operations performed on pipe lines, such as gas and water mains, require a hole to be dπlled in the pipe wall which must be plugged when the operation is complete Very often the plug must be fitted whilst the pipe is under pressure and in service For instance, it is known to perform maintenance operations on in service pipe lines by drilling and tapping a hole the pipe wall and then temporaπly sealing off a length of the pipe by inserting an inflatable bladder through the hole which can be inflated into contact with the pipe wall Such an operation is known as baggmg-off and is widely used particularly in relation to gas pipes The drilling operation, the installation of the inflatable bags, the removal of the inflatable bags when the operation is complete and plugging the hole in the pipe are all conducted whilst the pipe is pressuπsed

A wide variety of plug fittings are available for use in different applications Such fittings include tapered threaded plugs designed to be screwed into the hole in the pipe wall and plugs comprising rubber sealing members which are compressed against the pipe (which may be on the mside of the pipe wall, on the outside of the pipe wall, or within the πm of the hole) Many such fitting exist which can be fitted whilst the pipe is under pressure using conventional drilling and tapping apparatus

The suitability of any particular type of plug fitting for use in any particular application depends to a large extent on the mateπal from which the pipe is constructed and the nature of the fluid it carries In the case of steel pipes, which are for instance becoming increasingly widely used for gas mams, it is preferable to plug holes in the pipe wall by welding a fitting to the pipe wall (which is not, for instance, possible with cast iron pipes) Welded seals do not, for example, suffer the long term durability problems associated with rubber or threaded sealing systems

Welding a fitting to a pipe can however be problematical For instance, welding a fitting to a pressuπsed pipe carrying gas is particularly hazardous Measures have to be taken to ensure that gas cannot escape from the pipe dunng the welding operation The conventional method for overcoming this problem when performing bagging-off operations on steel gas pipes is to pre-weld a tapped boss to the outside of the pipe wall before a hole is dπlled m the pipe wall and thus before the bagging off operation When the baggmg-off operation is completed, and the equipment removed from the pipe, a threaded plug is screwed into the boss to provide a temporary seal whilst a cap is welded to the boss providing a permanent welded seal The boss must be provided to ensure that there is sufficient length of screwthread to provide an effective seal Simply screwing a plug into the hole in the pipe could not be guaranteed to provide a sufficiently effective seal, particularly bearing in mind that steel pipes are generally thinner than cast iron pipes

A problem with the conventional method descπbed above is that the existence of the boss presents difficulties when performing the dπllmg and bagging off operations, for instance placing height and diameter restraints on the equipment used

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

According to a first aspect of the present invention there is provided a plug fitting for plugging an aperture defined by a wall, the fitting compnsing a body portion for insertion into said aperture which in use anchors the fitting to the wall, a sealing member disposed around said body portion, compression means carried by the body portion which in use compresses the sealing member against the wall around said aperture, and a collar which surrounds the sealing member, wherein the collar is fabπcated from a weldable matenal which may be welded to the wall and the sealing member is fabricated from a heat resistant mateπal, such that in use the collar may be welded to the wall around said aperture to seal the fitting to the wall without breaking the seal provided by the sealing member

The present invention obviates the need to provide a boss on the wall since a temporary seal is provided by compressing a sealing member against the wall around the aperture The permanent welded seal can then be readily provided by welding the collar, which surrounds the sealing member, to the pipe wall Fabricating the sealing member from a heat resistant mateπal ensures that the integπty of the temporary seal is not compromised whilst the welding operation takes place Once the welding operation is complete, the temporary seal provided by the sealing member is redundant and thus the seal only needs to remain effective for the duration of the welding operation

It will be appreciated that a vaπety of mateπals could be used for the collar and sealing member In the case of the collar, this could be made from any mateπal which can be welded to the wall, and thus the mateπal from which the wall is made will have a beaπng on the suitable matenal for use as the collar For instance, if the fitting is to be used to plug holes in steel walls, such as steel gas pipes, then it is preferable that the collar is also steel In relation to the sealing member, this must be heat resistant in the sense that it must not fail dunng the welding operation It does not matter if the seal is damaged dunng the welding operation so that it subsequently fails, since once the weld is complete the seal provided by the sealing member is redundant

In prefeπed embodiments of the invention the collar is a separate component from the body portion In such embodiments, the body portion is also fabπcated from a weldable material so that the collar can be welded to the body portion to complete installation, the temporary sealing member thereby being encapsulated between the collar, the body portion and the wall

The compression means is preferably integral with said body portion and m particular is preferably an abutment shoulder defined by the body portion which exerts a compressive force on the sealing member as the body portion is inserted into the aperture For instance, with embodiments of the invention adapted for plugging a tapped hole, the body portion is preferably screw-threaded so that it may be screwed into the hole (this screw-threaded engagement providing both a means to anchor the fitting to the aperture and also to provide a partial seal) With such an embodiment, if the compression means is a simple shoulder provided by the body portion, the sealing member can be compressed against the pipe wall simply by screwing the body portion into the hole

Other prefeπed features of the plug fitting will be apparent from the following descπption and the appended claims According to a second aspect of the present invention there is provided a method of plugging an aperture in a wall using a plug fitting according to any preceding claim, comprising the steps of:

(i) inserting said body portion at least part way into said aperture to anchor the fitting to the wall and at least partially seal said aperture;

(ii) forcing said compression means to bear either directly or indirectly against the sealing member to compress said sealing member against said pipe wall to fully seal the aperture; and

(iii) welding said collar to the pipe wall to permanently secure and seal the fitting to the wall.

A specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which:

Figure 1 is a side elevation of a plug fitting according to the present invention installed in a hole in a pipe wall (looking along the axis of the pipe); and

Figure 2 is an exploded sectional view of the plug fitting of figure 1.

The illustrated fitting is designed for installation in a pre-drilled and tapped hole in the wall of a steel gas pipe whilst the pipe is under pressure. Apparatus for drilling and tapping holes in pipe walls whilst the pipe is under pressure is well known and will not be described in detail here. Such apparatus, which will be refeπed to as a "drilling and tapping machine" is, for instance, conventionally used to pre-drill holes in a hole in a pipe wall prior to a bagging off operation (as discussed above). The drilling and tapping apparatus is usually designed to allow a variety of different tools and equipment to be installed on a common machine platform.

Referring to the drawings, the plug fitting comprises a steel cylindrical plug body 1, an annular steel collar 2 and an annular graphite sealing gasket 3. The plug body 1 has a lower screw-threaded portion 4 and defines an annular shoulder 6 at its upper end. The screw-threaded portion 4 terminates approximately mid way along the length of the plug body 1 leaving a non-threaded portion 7 immediately beneath the shoulder 6. Plug body 1 , has a central square section socket 8 provided to enable the plug fitting to be mounted to appropriate installation apparatus (not shown).

The annular collar 2 comprises a cylindrical portion 9, the lower end of which is curved out of plane to match the curvature of the pipe 10 (so that it will "saddle" the pipe 10) and the upper end of which defines a radially inwardly projecting annular shoulder 11 which has an internal diameter smaller than the outer diameter of the annular shoulder 6

The gasket 3 compπses a nng dimensioned to be a close fit around the plug body 1 The axial length of the gasket is substantially the same as the axial length of the non-threaded portion 7 of the plug body 1, and its thickness is substantially equal to the radial width of the annular shoulder 11 of the collar 2 The lower edge of the gasket 3 is contoured similarly to the lower end of the collar 2 so that it will likewise saddle the pipe 10

The relative dimensions are such that the collar 11 fits closely around the plug body with the shoulder 11 beanng against the plug body shoulder 6, the cyhndncal portion 9 defining an annular recess around the portion 7 of the plug body 1 to receive the sealing gasket 3

Installation of the illustrated plug fitting is performed in three stages,

(1) The plug fitting is first assembled, mounted to a earner (not shown) and fitted to a conventional dπllmg and tapping machine (not shown) The dnlhng and tapping machine is then used to partially screw the plug body 1 into the tapped

(n) The dnlhng and tapping machinery is removed and the plug body 1 is screwed further into the hole to tighten the fitting against the pipe wall 10 In doing so, the annular shoulder 6 of the plug body 1 bears against the annular shoulder 1 1 of the collar 2 so that the gasket 3 is compressed between the pipe wall 10 and the collar 2

( ) Finally, with the fitting fully tightened the installation operation is completed by welding the collar 2 both to the pipe wall 10 (in the annular region indicated by reference 12) and to the plug body 1 (m the annular region indicated by the reference 13)

Use of conventional drilling and tapping machinery to perform the initial installation stage (l) allows the plug fitting to be installed into a hole in a pressuπsed pipe without permitting the uncontrolled escape of gas from the pipe The machinery must be removed before the fitting is finally tightened to enable the gasket and collar to be properly aligned with the pipe The screw-threaded engagement of the plug body 1 within the hole is not sufficient to completely prevent the escape of gas from the pipe 10, but is sufficient to limit leaking gas to an acceptable level whilst the second stage (n) of installation is performed Once stage (n) is complete, the graphite gasket provides a seal which completely prevents the escape of gas from the pressuπsed pipe 10 Termination of the screw-thread 4 short of the gasket 3 ensures there is no leakage path past the gasket It is then safe to complete the installation process by performing the welding operation (in) Since the graphite gasket is heat- resistant, the seal it provides will not be compromised dunng the welding operation

Although the graphite gasket 3 provides a complete seal against the escape of gas, the mtegπty of this seal cannot be relied upon long-term, rather the permanent seal is provided by the weld Once the welds are completed the seal provided by the gasket is effectively redundant, the gasket being provided to temporaπly seal the hole whilst the welding operation is completed

It will thus be seen that the present invention provides a relatively simple yet effective plug fitting which may be fitted to a hole in a pressunsed pipe without requiπng any modification to conventional dπllmg and tapping machinery or operations The invention therefore avoids the disadvantages associated with the provision of a boss according to the conventional methods for welding seals to a steel pipe In addition, although with the illustrated fitting two welded seams are formed, these may be done in an essentially single operation, whereas with the pπor art methods described above a first welding operation must be performed to attach the boss prior to dnlhng a hole in the pipe, further by a further welding operation to seal a cap to the boss once the bagging-off procedure etc is completed

Although the above fitting has been descnbed for use in sealing a hole in a gas pipe, it will be understood that the fitting could be used in other applications Similarly, the fitting is not restricted to use with steel pipes, but could be used in relation to any pipe which will support a welding operation Neither is the fitting limited to sealing holes in pipes, rather it will be appreciated that the fitting could readily be modified for use in other situations, for instance for sealing a hole in a flat wall such as the wall of a fluid containin^g tank Although the fitting descnbed above is particularly useful for sealing holes in pipes carrying gas or a similarly flammable fluid, it is not limited to such application The fitting could, for instance, be used to plug holes in water pipes

It will be appreciated that since the earner effectively provides an adapter to enable the fitting to be fitted to conventional dnlhng and tapping machinery, the exact form of the earner may vary Use of an intermediate earner to mount the fitting to the dnlhng and tapping machinery avoids the need to provide different plug fitting designs for use with different machinery

The precise dimensions of the vanous elements of the plug fitting will vary depending upon the size of the hole to be plugged, and the size of the pipe, and thus the relative sizes of the components of the fitting could be modified accordingly

Whilst the curvature of the lower edge of the gasket 3 (which is substantially ngid) must closely match the curvature of the pipe 10 to provide a good seal, it is not absolutely necessary that the curvature of the lower edge of the collar 2 matches the curvature of the pipe It is, however, preferred that the curvature of the collar 2 at least approximately matches the curvature of the pipe to make it easier to weld the collar 2 to the pipe 10 to complete the installation However, the lower edge of the collar could simply have a circular profile with no curvature out of plane, although this would mean that the gap to be bridged by the weld would be greater at some points than others once the fitting is installed With such a configuration the collar could be provided as an integral component of the plug body (dispensing with the shoulder 6) which would not be possible with the curved collar 2 illustrated, since the curvature of the collar would prevent it from rotating relative to the pipe 10 as the fitting is screwed into the hole The disadvantage of having to weld across a larger gap to weld the collar to the pipe would be to some extent offset by the fact that only a single weld would be required with such an embodiment

As a further possible modification, the annular shoulder 6 could be replaced by a nut or the like which is screwed onto the plug body 1 to dπve the collar 2 along the length of the body and compress the gasket 3 against the pipe wall

The collar 2 need not have an annular shoulder 1 1 , but could be a simple sleeve which slides over the gasket 3 and which could, for instance, be positioned after the gasket has been compressed against the pipe wall (the temporary seal m this instance being provided between the pipe wall, the gasket and the annular shoulder 6 (or equivalent)).

It will be appreciated that the gasket need not be fabricated from graphite but could be fabricated from any material which is capable of providing both a good (albeit temporary) seal against the pipe wall and which is resistant to melting at the temperatures at which the welding operation is performed. It may even be permissible for the gasket to soften, and perhaps even partially melt, during the welding operation provided the integrity of the temporary seal is not compromised.

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

Claims

1. A plug fitting for plugging an aperture defined by a wall, the fitting comprising: a body portion for insertion into said aperture which in use anchors the fitting to the wall; a sealing member disposed around said body portion; compression means carried by the body portion which in use compresses the sealing member against the wall around said aperture; and, a collar which surrounds the sealing member; wherein the collar is fabricated from a weldable material which may be welded to the wall and the sealing member is fabricated from a heat resistant material, such that in use the collar may be welded to the wall around said aperture to seal the fitting to the wall without breaking the seal provided by the sealing member.

2. A plug fitting according to claim 1, wherein said collar is a separate component from said body portion, and wherein said body portion is fabricated from a weldable material such that with the plug fitting installed in said aperture said collar may be welded to said body portion to encapsulate said sealing member between the collar, the body portion, and the pipe wall.

3. A plug fitting according to claim 2, wherein said compression means is integral with said body portion, whereby said sealing member is compressed against said wall by insertion of said body portion into said aperture.

4. A plug fitting according to claim 3, wherein said compression means comprises a surface defined by said body portion which bears directly or indirectly against said sealing member.

5. A plug fitting according to any preceding claim, wherein said compression means comprises an abutment shoulder extending from said body portion.

6. A plug fitting according to any preceding claim, wherein said collar has a shoulder portion which lies between said compression means and said sealing means and is brought to bear against said sealing means by said compression means.

7. A plug fitting according to any preceding claim, wherein said collar substantially shrouds the sealing member.

8. A plug fitting according to any preceding claim, wherein said body portion is a close fit within said aperture to provide at least a partial seal.

9. A plug fitting according to any preceding claim for plugging a circular aperture, wherein the body portion has a circular cross-section and said sealing member and collar are annular.

10. A plug fitting according to 9, wherein said compression means is annular.

11. A plug fitting according to claim 9 or claim 10 for plugging a tapped aperture, wherein said aperture is tapped and wherein said body portion has a first end which is screw-threaded whereby the body portion may in use be screwed into said aperture.

12. A plug fitting according to claim 1 1, wherein said body portion has a non- screw-threaded portion disposed between said compression means and said screw- threaded portion, said sealing member being disposed around said non-screw-threaded portion.

13. A plug fitting according to any preceding claim, wherein said collar is cupped to provide an annular recess which receives and at least partially shrouds said sealing member.

14. A plug fitting according to any preceding claim for plugging an aperture in a curved wall, such as the wall of a pipe, wherein the sealing member has a contoured portion which corresponds to the curvature of the wall so that the sealing member conforms to the curvature of the wall when compressed against the wall around said aperture.

15. A plug fitting according to 14, wherein the collar has one end profiled to correspond substantially to the curvature of the wall.

16. A plug fitting according to any preceding claim, wherein the sealing member is substantially rigid.

17. A plug fitting according to any preceding claim, wherein the sealing member is fabricated from graphite.

18. A plug fitting according to 1, wherein said compression means comprises a member which is moveable relative to said body portion whereby said sealing means is in use compressed against said wall by moving said compression member along said body portion.

19. A plug fitting according to 1, wherein said collar is integral with, or fixed in position relative to, said body portion and provides said compression means.

20. A plug fitting according to 1 , wherein said compression means bears directly on said sealing member.

21. A method of plugging an aperture in a wall using a plug fitting according to any preceding claim, comprising the steps of:

(ii) forcing said compression means to bear either directly or indirectly against the sealing member to compress said sealing member against said wall to fully seal the aperture; and

(iii) welding said collar to the wall to permanently secure and seal the fitting to the wall.

22. A method according to claim 21, comprising the additional step of welding said collar to said body portion to encapsulate said sealing member between said collar, said body portion and said wall.

23. A plug fitting substantially as hereinbefore described, with reference to the accompanying drawings.

24. A method of plugging an aperture in a pipe wall, substantially as hereinbefore described, with reference to the accompanying drawings.