WO1998022745A1

WO1998022745A1 - Expandable sealing plug

Info

Publication number: WO1998022745A1
Application number: PCT/GB1997/003158
Authority: WO
Inventors: Andrew David Giddings
Original assignee: Avdel Textron Limited
Priority date: 1996-11-19
Filing date: 1997-11-18
Publication date: 1998-05-28
Also published as: GB2314904B; GB2314904A; AU4960597A; GB9623985D0

Abstract

An expandable sealing plug assembly suitable for sealing an opening in a body or workpiece such as a pipe wall, said plug comprising in the assembled state prior to the sealing process: (i) a sleeve (10) open at one end and having a wall at the other end forming in effect a cylinder closed at one end, the sleeve being adapted to be inserted closed end first into the opening to be sealed, the closed end of the sleeve protruding beyond the inside face of the workpiece; (ii) an elongate sealing member having stem (12) and an enlarged head (18), the head being located substantially at the closed end of the sleeve and the stem extending beyond the open end of the sleeve, the inner surface of the sleeve being adapted to encapsulate at least the head of the sealing member within the sleeve, such that the sleeve and sealing member combination as assembled prior to undergoing the sealing process are so sized, shaped and adapted such that during the sealing operation the entire sealing member can be withdrawn from the sleeve to leave the sleeve in sealing contact with the opening and the inside of the sleeve cylinder substantially free from any obstruction and wherein the stem incorporates a weakened region (19) on the proximal side of the head, the head being thereby adapted to be broken away from the stem at the weakened region after the sealing member has been withdrawn from the sleeve.

Description

EXPANDABLE SEALING PLUG Field of the Invention

The present invention relates to expandable plug devices of the type used to close and preferably seal openings in a workpiece. It is particularly applicable but in no way restricted to devices and methods for sealing an opening or bore through the wall of a pipe. Background to the Invention

Pipes and coil tubing are used extensively in oil field work and other down hole situations. Coiled tubing is used to perform a variety of maintenance tasks on both complete and incomplete oil and gas wells. Tool strings can be lowered many thousands of feet down into the well to carry out the necessary operations. On occasions it is necessary to form a penetration in the side wall of such pipes and tubing so that a passage or opening is created through the wall to give a connection between the inside and outside of the pipe. One way of achieving this presently is to use a threaded plug which is inserted into a threaded bore in the side wall of the pipe. The plug is essentially in the form of a hollow cylindrical sleeve with one end closed off by an end wall. The plug is inserted closed end first and screwed into the opening such that the plug protrudes into the bore of the pipe on the inside but is flush with, or slightly inset, with respect to the outside surface of the pipe. When a permanent opening is required a cutting tool is sent down the pipe to shear off the exposed end of the plug. Once the closed end of the plug has been removed this leaves a free passage between the inside and the outside of the pipe.

This method suffers from a number of disadvantages. It requires a tapped hole to be formed in the pipe wall at the manufacturing stage as and when required. Whilst it is relatively easy to drill a hole through the pipe wall, this hole then has to be tapped. If this operation is not done carefully then the seal around the plug will be incomplete. When the tapping operation is done manually it requires considerable strength and skill on the part of the operator. In any event, expensive tapping equipment is required. It is also a time-consuming and laborious operation.

Expandable sealing plugs are known per se. For example, GB 1 249 517 (Pneumo Dynamics Corporation) describes a cylindrical sealing plug or sleeve closed at one end with a tapered interior surface, tapering towards the open end, and a sealing or locking member with a tapered head. As the locking member is withdrawn whilst restraining the plug in place the head of the locking member is drawn down the taper, causing radial expansion of the sleeve and its outer surface is swaged into sealing contact with the passageway into which it is inserted. At some point along its path and before it can exit the sleeve, the head of the locking member is sheared from the stem. The head therefore becomes a permanent feature of the plug after swaging.

Such expandable plugs have been used to seal passageways into the housings of hydraulic valves and the like where the sealing plug does not extend beyond the end of the passageway and into the valve body. Even if the type of plug were used to seal an opening in a pipe wall, it would not be possible to recreate an opening by shearing off the closed end of the sleeve because the head of the stem blocks any passage. GB 1 218 492 describes a method and apparatus for plugging the rear end of a tubular passage which is only accessible from the front. In this case a mandrel is used to expand the side walls of a plug. However, the head of the mandrel is not detachable. As a consequence the mandrel cannot be withdrawn from the pulling tool by continuing the pulling action. The tool must be removed from the workpiece and the mandrel then withdrawn from it. This makes repeated operated of the tool laborious.

GB 1 207 790 (Waagner-Biro Aktiengesellschaft) describes a complex apparatus for plugging heat exchanger tubes. This apparatus is designed to swage the side wall of a plug against the side wall of a tube and is quite unsuitable for operating on the outside wall of coil tubing. In addition, the expander used to swage the wall of the plug against the side wall of the tube has no facility for snapping off the head of the expander to facilitate withdrawal.

It is an object of the present invention to provide a sealing plug device and method which overcomes some or all of these disadvantages.

Summary of the Invention

According to a first aspect of the present invention there is provided an expandable sealing plug assembly suitable for sealing an opening in a body or workpiece such as a pipe wall, said plug comprising in the assembled state prior to the sealing process:-

(i) a sleeve open at one end and having a wall at the other end forming in effect a cylinder closed at one end, the sleeve being adapted to be inserted closed end first into the opening to be sealed, the closed end of the sleeve protruding beyond the inside face of the workpiece; (ii) an elongate sealing member having a stem and an enlarged head, the head being located substantially at the closed end of the sleeve and the stem extending beyond the open end of the sleeve, the inner surface of the sleeve being adapted to encapsulate at least the head of the sealing member within the sleeve, such that the sleeve and sealing member combination as assembled prior to undergoing the sealing process are so sized, shaped and adapted such that during the sealing operation the entire sealing member can be withdrawn from the sleeve to leave the sleeve in sealing contact with the opening and the inside of the sleeve cylinder substantially free from any obstruction; and wherein the stem incorporates a weakened region on the proximal side of the head, the head being thereby adapted to be broken away from the stem at the weakened region after the sealing member has been withdrawn from the sleeve.

This has the advantage that it provides, for the first time, a plug which provides an internal overhang inside the workpiece which can be removed when desired to create a patent passageway. The plug can easily be installed using a mechanical tool in which the spent and broken stem can be removed by continuing to withdraw it in the same general direction as that involved in the sealing movement. The tool is thus quickly ready for use on a subsequent plug.

Preferably the weakened region is formed by an undercut. Preferably the head is tapered to provide wedge expansion of the inner surface of the sleeve as the sealing member is withdrawn in use. A hardened taper provides consistent and reliable swaging of the plug against the opening.

The outer surface of the sieeve may incorporate one or more annular peripheral grooves. These grooves tend to result in a stronger seal since they both bite into the bore surface and provide space for swaged material to occupy.

Preferably the sleeve is made of aluminium or an aluminium alloy. This type of material is relatively easy to shear and can also be dissolved chemically if need be.

According to a second aspect of the present invention there is provided a method of sealing an opening in a body or workpiece such as a pipe wall comprising the steps of:- (a) providing an expandable sealing plug assembly as described above;

(b) inserting the plug into the opening to be sealed with the closed end of the plug sleeve leading, such that the distal end of the plug projects beyond the furthest face of the opening; (c) supporting the sleeve against axial movement out of the opening such that the proximal end of the sleeve is inset within the opening; (d) retracting the sealing member, including the head, from the sleeve causing the distal end of the sleeve to expand behind the opening and to swage the sleeve into sealing contact with the bore of the opening; and (e) breaking off the head of the sealing member at the weakened region once the head has exited the sleeve.

The invention also extends to cover the process for forming the assembled sealing plug as illustrated. Brief Description of the Drawings The invention will be further described, by way of example, with reference to the accompanying drawings in which:-

Figure 1 illustrates a cross-section of an assembled sealing plug according to the first aspect of the invention;

Figures 2 and 3 show the components of the sealing plug of Figure 1 prior to assembly.

Figure 4 shows an assembly sequence resulting in a finished sealing plug; Figure 5 shows a sealing plug installation sequence according to the second aspect of the invention;

Figure 6 shows a variation of the invention in which only the head of the plug stem is encapsulated within a sleeve. Description of Preferred Embodiments

Embodiments of the present invention are described below by way of example only. These examples represent the best ways of putting the invention into practice that are currently known to the Applicant although they are not the only ways in which this could be achieved.

Referring to Figure 1 , this illustrates a plug sleeve 10 encapsulating the head end 18 of a stem 12. The sleeve is closed at one end 13, referred to here as the distal end, by end face 14. The components or direction furthest from the closed end of the sleeve will be referred to as proximal. The sleeve is thus in the form of a cylinder closed at one end with an outer surface 15 adapted for placement in a tubular passage through a workpiece such as a pipe wall. The inner surface 16 of the sleeve substantially conforms to the shape of the headed stem encapsulated within it.

The outer surface of the sleeve can incorporate one or more longitudinally spaced annular grooves (not shown) with resulting intervening lands. These are known to enhance the seal formed between the sleeve and the passage in certain applications.

The stem, which acts as a sealing member when withdrawn, is made from a material which is harder than the sleeve such that when the stem is withdrawn the head of the stem will deform the sleeve. The stem 12 comprises a shaft 17 and head 18. The stem is peripherally undercut at 19 immediately adjacent the head 18 such that the stem can be broken at this weakened section by tensile loading.

Part 20 of the outer surface of the head is generally tapered or frusto-conical in shape with the larger end of the taper towards the closed or distal end of the sleeve. The individual components from which the plug assembly is constructed are shown in Figures 2 and 3. A similar numbering sequence to that used in Figure 1 has been adopted in Figures 2 and 3 for ease of reference.

A hardened steel stem 32 is manufactured using conventional techniques. The angle between opposite faces of the taper 40 is typically 25°. The angles A, B and C between the various elements of the sleeve as shown in Figure 3 are 15°, 34° and 90° respectively. The process by which the sealing plug assembly is formed is best illustrated in Figure 4. The stem 32 is introduced head first into sleeve 30 (Figures 4(a) and 4(b) ) and the components are offered into a die (Figure 4(c) ) whose inside opening corresponds in diameter and cross-section to the opening or bore in the workpiece which is eventually to be sealed. The sleeve is then urged through the die in a swaging process as shown in Figure 4(c) and (d) to produce the finished sealing plug assembly Figure 4(e).

The sealing plug installation sequence will now be discussed in detail, with reference to sealing an opening in a pipe wall as shown in Figure 5. The sealing plug assembly 41 is offered into an opening or bore 42 in a pipe wall 43. The plug is positioned such that the portion of the sleeve occupied by the stem head 18, 38 extends well inside the pipe. It is important that the initial outward movement of the stem causes the sleeve to expand on the inside of the pipe. The sealing plug may be installed by means of a suitable conventional hydro- pneumatic breakstem fastener installation tool fitted with a nose tip 44. The tool incorporates a means (not shown in Figure 5) of gripping and pulling the shaft 17, 37 of the stem 12, 32 and an annular nose tip which acts on the sleeve as an anvil. The nose tip includes a central recess to accommodate the stem head, surrounded by an annular boss which extends into the end of the bore 42 to support the end of the sleeve; the boss is surrounded by a radial flange which locates against the outer face of the pipe wall. As the stem is withdrawn the sleeve deforms as shown in Figures 5(b) and 5(c) to seal the sleeve into the opening. The nose tip ensures that no part of the sleeve extends proud of the outside surface of the pipe. It also accommodates the complete stem head to ensure that this finishes completely clear of the sleeve at the end of the sealing operation. The head can then be snapped off by continued outward tensile force applied to the shaft by the tool. The shaft 17, 37 can then be fully withdrawn and removed from the tool by continuing the pulling force in a direction generally perpendicular to and away from the workpiece. The tool is therefore immediately ready for re-use on a subsequent sealing plug.

The materials of construction of the various components described above can be determined by the materials specialist. These will include hardened steel for the stem and aluminium or aluminium alloys for the sleeve. Aluminium has the advantage that not only is it ductile but it can also be dissolved away chemically by applying strong mineral acids.

A slightly modified form of sealing plug assembly is illustrated in Figure 6, which corresponds to Figure 4(c). The sleeve encapsulates (i.e. is in contact with) the head of the plug stem, but not the shaft thereof (i.e. there is an annular gap between the inside of the sleeve and the shaft).

Claims

1. An expandable sealing plug assembly suitable for sealing an opening in a body or workpiece such as a pipe wall, said plug comprising in the assembled state prior to the sealing process:- (i) a sleeve open at one end and having a wall at the other end forming in effect a cylinder closed at one end, the sleeve being adapted to be inserted closed end first into the opening to be sealed, the closed end of the sleeve protruding beyond the inside face of the workpiece; (ii) an elongate sealing member having a stem and an enlarged head, the head being located substantially at the closed end of the sleeve and the stem extending beyond the open end of the sleeve, the inner surface of the sleeve being adapted to encapsulate at least the head of the sealing member within the sleeve; such that the sleeve and sealing member combination as assembled prior to undergoing the sealing process are so sized, shaped and adapted such that during the sealing operation the entire sealing member can be withdrawn from the sleeve to leave the sleeve in sealing contact with the opening and the inside of the sleeve cylinder substantially free from any obstruction and wherein the stem incorporates a weakened region on the proximal side of the head, the head being thereby adapted to be broken away from the stem at the weakened region after the sealing member has been withdrawn from the sleeve.

2. A sealing plug as claimed in Claim 1 wherein the weakened region is formed by an undercut.

3. A sealing plug as claimed in any preceding Claim wherein the head is tapered to provide wedge expansion of the inner surface of the sleeve as the sealing member is withdrawn in use.

4. A sealing plug as claimed in any preceding Claim wherein the outer surface of the sleeve incorporates one or more annular peripheral grooves.

5. A sealing plug as claimed in any preceding Claim wherein the sleeve is made of aluminium or an aluminium alloy.

6. A method of sealing an opening in a body or workpiece such as a pipe wall comprising the steps of:- (a) providing an expandable sealing plug assembly as claimed in any preceding Claim;