GB2243428A

GB2243428A - A pipe plug

Info

Publication number: GB2243428A
Application number: GB9009605A
Authority: GB
Inventors: Kenneth Samuel Hemingway
Original assignee: International Pipeline Products Ltd
Current assignee: International Pipeline Products Ltd
Priority date: 1990-04-28
Filing date: 1990-04-28
Publication date: 1991-10-30
Anticipated expiration: 2010-04-28
Also published as: GB9009605D0; GB2243428B

Abstract

A pipe plug (1) comprises a sealing device (3) comprising two inflatable tyres 3, 4 which are independently inflatable. A sealing plug (14) in the pipe plug (1) allows fluid to pass through the pipe plug (1) while it is moving along a pipe. When the pipe plug (1) is in an appropriate position along the pipe, the sealing plug (14) prevents further flow of liquid through the pipe plug (1). The tyres 3, 4 are inflated and a seal if formed. The plug may be used during the underwater welding of pipe-sections as shown in Fig 2. A valve 14 to control through-fluid-flow may be provided. <IMAGE>

Description

A PIPE PLUG This invention relates to a pipe plug for use in sealing a pipe section while maintenance or repair operations are carried out. and particularly. but not exclusively. to a pipe plug for use in a pipe carrying liquid.

It is often necessary to carry out maintenance or repair operations on pipe sections which are situated at the bottom of the sea. In such a situation the pipe plug must be capable of withstanding substantial differential pressure action across opposed faces of the pipe plug.

A known pipe plug comprises a body portion, and an annular sealing device attached around the surface of the body portion and inflatable so as to move into sealing contact with an annular surface of the pipe section. In use two of these pipe plugs are positioned on each side of the pipe section to be repaired, and each sealing device is inflated to form a seal. It is necessary for safety reasons to use a minimum of two pipe plugs to form a seal in order that if one sealant device fails to inflate properly, or deflates, the other one continues to provide the seal. The necessity of using pairs of pipe plugs in this manner is costly. in order that if one sealant device fails to inflate. or deflates, the other one continues to provide the seal. The necessity of using pairs of pipe plugs in this manner is costly.

In addition, in order that a pipe plug may be moved freely through the pipe to the appropriate pipe section, the cross-sectional area of the body portion, together with the uninflated sealing device, must be substantially smaller than that of the pipe. This results in a requirement for a large clearance between the pipe plug and the pipe. to facilitate the movement of the pipe plug through the pipe. A disadvantage of this, is that the sealing device must be large enough. when inflated, to fill the large clearance existing between the pipe and the pipe plug. This tends to result in unpredictable behaviour of the pipe plug during inflation of the sealing device.

According to a first aspect of the present invention, there is provided a pipe plug for use in sealing a pipe section and comprising a body portion; and an annular sealing device attached around the surface of the body portion and inflatable so as to move into sealing contact with an annular surface of the pipe section, characterised in that the sealing device comprises a plurality of inflatable tyres, each of which is independently inflatable.

By forming the sealing device from a plurality, typically two, of inflatable tyres which are each independently inflatable, the safety advantage of having two or more independently inflatable types may be acheived without the expense of having to use two or more pipe plugs.

According to a second aspect of the present invention there is provided a pipe plug for use in sealing a pipe section and comprising a body portion; and an annular sealing device attached around the surface of the body portion and inflatable so as to move into sealing contact with an annular surface of the pipe section, characterised in that the pipe plug further includes valve means for allowing fluid to pass through the body portion.

By including the valve means in the body portion, fluid being carried by the pipe may be allowed to flow through the pipe plug while the pipe plug is being moved along the pipe to the appropriate pipe section. The fluid will flow through the pipe plug in an opposite direction to the direction of movement of the pipe plug, and will enable the pipe plug to be moved easily along without the necessity of having a large clearance between the pipe plug and the pipe, when the sealing device is in its uninflatable state. The sealing device need only be inflated to fill a relatively small gap, and the behaviour of the pipe plug during inflation is relatively more predictable. Once the pipe plug is in the appropriate position, the valve means will no longer allow fluid to pass through the pipe plug, in order that a seal may be formed.

Advantageously, the tyres are inflatable polyurethane tyres, and each tyre is separated from an adjacent tyre by means of an annular middle plate.

Preferably, the annular sealing device is held captive axially within a housing formed by a pair of axially spaced annular end plates. Thus, during inflation, the sealing device is restrained from expanding axially. When the sealing device comprises a plurality of inflatable tyres, the annular middle plate or plates separating adjacent tyres act in conjunction with the annular end plates to axially restrain each tyre, Preferably, the valve means is a sealing plug positioned in a bore running along the length of the pipe plug. When the pipe plug is being moved along the pipe, the sealing plug is removed from the bore, in order that fluid may flow along through the bore and thus allow free movement of the pipe plug along the pipe. When the pipe plug is in the appropriate position along the pipe, the sealing plug is repositioned in the bore to allow a seal to be formed.

Preferably, the pipe plug further comprises a plurality of discs, axially spaced along the body portion.

These discs serve to align the pipe plug in the pipe before the sealing device has been inflated, and thus restrict radial movement of the pipe plug from moving around within the pipe.

The invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a schematic diagram of a pipe plug made in accordance with the invention; and Figure 2 is a schematic view showing one use of pipe plugs in accordance with the invention Referring to figure 1, a pipe plug (1) according to the invention comprises a body portion (2) having a substantially circular cross-section. Attached to the body portion (2) is a sealing device comprising two tyres (3) (4).

Tyre 3 is inflatable via pipe (5) which is connected to tank (6) containing compressed air. Tyre 4 is inflatable via pipe (7) which is connected to a tank (8) containing compressed air. The two tyres 3, 4, may thus be independently inflatable. The tyres 3, 4, each have a grooved surface (9) which enables the tyres 3, 4 to grip onto the surface (10) of a pipe when the tyres are inflated. This restrains axial movement of the pipe plug (1).

The tyres 3, 4 are separated from one another by an annular plate (11). Annular end plates (12) serve to restrict axial expansion of the tyres 3, 4 during expansion. Discs (13) spaced axially along the body portion (2) serve to align the pipe plug (1) in a pipe when the tyres 3, 4 are not inflated. A sealing plug (14) is positioned within a bore (not shown) extending along the length of the pipe plug (1).

In use, the pipe plug (1) is inserted into a pipe (10) carrying, for example a liquid. The diameter of such a pipe is typically 16 inches. On inserting the pipe plug (1) into the pipe, the tyres 3, 4 are uninflated, and the sealing plug (14) is in an open position. The pipe plug is moved along the pipe to an appropriate point. While it is moving, liquid may pass through the pipe plug (1), as the sealing plug (14) is in an open position. Because liquid may pass through the pipe plug (1), the clearance between the walls of the pipe, and the pipe plug (1) may be relatively small. typically 1 inch. When the pipe plug (1) is at the appropriate position, the sealing plug (14) is moved into a closed position to stop further flow of liquid through the pipe plug (1). The tyres 3, 4, are each inflated with compressed air from respective tanks 6, 8 via respective pipes 5, 7. In their inflated state, the tyres 3, 4 form a seal with the walls of the pipe.

The plug may be positioned at one end of a pipe section which is to be joined to a further pipe length e.g.

a connecting length of pipe to be joined between the ends of two existing pipe lengths as shown in Figure 2.

A pipe end (20) is to be joined to a pipe end (21) via a connecting length (22) which is welded to each of the pipe ends 20, 21. This can be carried out on the sea bed in a dry habitat (23), and with the liquid in the pipe ends 20, 21 held back by respective plugs (24).

Claims

1. A plug for use in sealing a pipe section and comprising a body portion; and an annular sealing device attached around the surface of the body portion and inflatable so as to move into sealing contact with an annular surface of the pipe section. Characterised in that the sealing device comprises a plurality of inflatable tyres, each of which is independently inflatable.

2. A pipe plug for use in sealing a pipe section and comprising a body portion: and an annular sealing device attached around the surface of the body portion and inflatable so as to move into sealing contact with an annular surface of the pipe section characterised in that the plug further includes valve means capable of allowing fluid to pass through the body portion

3. A pipe plug as claimed in claim 1 wherein the body portion further comprises valve means capable of allowing fluid to pass through the body portion.

4. A pipe plug as claimed in claim 2 wherein the sealing device comprises a plurality of inflatable tyres, each of which is independantly inflatable.

5. A pipe plug as claimed in claim 1 or claim 4 wherein the inflatable tyres each comprise inflatable polyurethane tyre.

6. A pipe plug according to claim 1, 4, or 5 wherein each of the plurality of inflatable tyres is separated from an adjacent tyre by means of a middle annular plate.

7. A pipe plug according to any of the preceding claims wherein the annular sealing device is held captive axially within a housing formed by a pair of axially spaced annuar end plates.

8. A pipe plug as claimed in any one of claims 2 to 7 wherein the valve means is a sealing plug positioned in a bore running along the length of the pipe plug.

9. A pipe plug as claimed in any one of the preceding claims further comprising a plurality of discs, axially spaced along the body portion.

10. A pipe plug substantially as hereinbefore described with reference to the accompanying drawings.