GB2273137A

GB2273137A - Branch pipe connection

Info

Publication number: GB2273137A
Application number: GB9314003A
Authority: GB
Inventors: George Albert Lees; Stuart Nigel Godfrey
Original assignee: UPONOR ALDYL Ltd
Current assignee: UPONOR ALDYL Ltd
Priority date: 1992-10-17
Filing date: 1993-07-07
Publication date: 1994-06-08
Anticipated expiration: 2013-07-07
Also published as: GB9221843D0; GB2273137B; GB9314003D0

Abstract

A method of fitting or replacing a branch tee in a gas distribution main is disclosed. An adaptor 1 is inserted into a hole in a wall of the distribution main, and the adaptor has a rigid body 2 with an internal bore 3 therein, the internal bore 3 being provided with a displaceable blocking means 10. A service pipe 16 is inserted into the internal bore 3 of the adaptor l so as to displace the blocking means 10 and open the internal bore 3 of the adaptor 1, and sealing means 9, 14, 15 is provided between the distribution mean and the adaptor 1 and between the adaptor 1 and the service pipe 16 such that the service pipe 16 is connected to the distribution main in a gas-tight manner. <IMAGE>

Description

BRANCH-OFF CONNECTION This invention relates to a method of making a branch-off connection, and more particularly to a method of providing a branch-off connection to a gas distribution main.

Gas distribution mains normally consist of a cast iron gas pipe which is laid in the ground. In order for a subscriber to be connected to the main, a tee connection is made in which an externally threaded metal tee piece is inserted into a screw-threaded bore formed in the wall of the gas main. The tee piece has an annular screw-threaded bore which is provided with a top cap and a screw-threaded plug which can be accessed by removal of the cap. A side pipe for connection to the consumer service pipe is connected to the bore at a point intermediate its ends.

The replacement of a tee piece is a difficult and costly operation. First a hole must be dug in the ground and the tee piece and distribution main exposed. The cap of the tee piece is then removed and the plug wound down until it is below the level of the side pipe. The service pipe connection to the consumer is then sawn off. Next a bell having two compartments connected by a slide valve is placed over the tee piece and secured in a gas-tight fashion by chainstepassing around the distribution main. With the slide valve open the tee piece is unscrewed and lifted into the top chamber of the bell. The slide valve is then closed and the top chamber of the bell evacuated of gas so that the tee piece can be removed.A new tee piece that may be metal or plastic, but at least has the possibility of connection to a plastic subscriber service pipe is then inserted into the bell. The new tee piece has its plug wound down so that, when the slide valve is opened and the tee piece screwed into the distribution main, the plug effectively prevents any gas from escaping. Finally the subscriber service pipe is connected to the side pipe, the system pressure tested, and the plug wound up in order to allow gas to flow along the subscriber service pipe. The top cap is then replaced to ensure the gas-tightness of the tee piece.

It can be seen from the above that the replacement procedure is both difficult and time consuming. In addition, the tee piece is an expensive item.

We have now devised a new method of fitting or replacing a branch tee which requires fewer method steps and can be accomplished with less expensive components.

The present invention provides a method of fitting or replacing a branch tee in a gas distribution main which comprises: inserting an adaptor into a hole in a wall of the distribution main, the adaptor having a rigid body with an internal bore therein, the internal bore being provided with a displaceable blocking means, and inserting a service pipe into the internal bore of the adaptor so as to displace the blocking means and open the internal bore of the adaptor, there being provided sealing means between the distribution main and the adaptor, and between the adaptor and the service pipe, such that the service pipe is connected to the distribution main in a gas-tight manner.

Preferably the adaptor has a screw-threaded external section which cooperates with a screw-threaded hole in the gas distribution main. An external annular seal is preferably also provided on the adaptor, which may, for example, comprise an O-ring seated in a recess in an annular flange.

The internal bore of the adaptor need not be threaded, thus saving on manufacturing costs, but is desirably provided with an internal annular seal to seal the bore against the external wall of the service pipe. The internal annular seal may, for example, comprise annular gas seals and end-loading rings.

The displaceable blocking means may, for example, comprise a rupturable wall or membrane, but is preferably a knock-out plug which may, for example, be seated in a recess at the distribution main end of the internal bore of the adaptor.

The service pipe may be a straight pipe, but is preferably an elbow, and most preferably a 900 elbow. The pipe may, for example, be made from a plastics material, such as, for example, polyethylene or an olefin polymer or copolymer. The wall of the pipe which is inserted into the adaptor is preferably reinforced with an internal metal insert. The insert may be tubular in cross-section, and of length from about 2 to 4 cms. In a preferred configuration, the reinforced end of the service pipe is configured so as to surround and fit tightly around the insert.

The rigid body of the adaptor may be moulded or cast as appropriate. Preferably the body of the adaptor is formed from a plastics material, such as, for example Delrin, and is injection moulded.

Instead of, or in addition to the internal annular seal of the bore of the adaptor, the service pipe may be provided with external lugs or indentations which themselves form a seal or cooperate with the internal annular seal to improve the gastightness of the joint.

The act of pushing the service pipe into the annular bore will normally be sufficient to displace the blocking means, but if desired the pipe or the metal insert may be provided with serrated or castellated legs or teeth to provide openings or leak paths through which gas can pass to equilibrate the gas pressure on each side of the displaceable blocking means and avoid the possibility that the blocking means may be retained by differential gas pressure on the end of the service pipe.

The legs or teeth may also be used to cut through the displaceable blocking means in certain embodiments.

In another aspect the invention also provides an adaptor for use in the above method which comprises a rigid body having an internal bore therein, the internal bore being provided with a displaceable blocking means and an internal annular seal, the body having a screw-threaded external section and an external annular seal.

In an especially preferred embodiment according to the invention, there is provided a security means which, when in place, prevents the service pipe from being pushed or driven sufficiently far into the annular bore to displace the blocking means. The security means may, for example, comprise a Cshaped collar which can be positioned around the service pipe, engaging with, for example, an annular flange, ledge, recess, rim, or collar on the service pipe, and such that it rests on a rim or other portion of the body of the adaptor, preventing the service pipe from being pushed or driven further into the adaptor. In a preferred method according to the invention, the security means is removed to allow the service pipe to be pushed or driven into the adaptor to displace the blocking means, and the pipe is then pulled back to allow the security means to be replaced. The security means thus prevents accidental movement of the service pipe in use, which could tend to displace the internal annular seal.

An example of a method and adaptor according to the invention will now be described with reference to and as illustrated in the accompanying Drawings in which: Figure 1 shows a first adaptor according to the invention and an elbow service pipe in sectional side elevation; Figure 2 shows a plan view of the adaptor of Figure 1; Figure 3 shows a service pipe for use with the invention; Figure 4 shows a pre-assembled second adaptor and elbow service pipe according to the invention in sectional side elevation; and Figure 5 shows a plan view of the security clip of Figure 4.

Referring to Figures 1 to 3 of the Drawings, the adaptor, designated generally at (1), comprises a body portion (2) having an annular internal bore (3). The body has an upper external polygonal section and a lower external threaded section (4), which is adapted to cooperate with the internal threaded bore of the hole in a distribution main. External annular sealing means (5), situated between the upper polygonal section and the lower threaded section, comprise an annular flange (6) having a face (7) within which is located a recess (8). Within the recess is seated an O-ring (9) of resilient polymeric material.

The internal bore (3) of the adaptor is provided with a knock-out plug (10) which is seated in a recess (11) in the distribution main end of the internal bore (3). Further annular recesses (12), (13) in the upper part of the internal bore (3) house pairs of gas seals and end-loading rings (14), (15) respectively.

The service pipe (16), formed from a suitable grade of high-density polyethylene, has an elbow (17) and a reinforced section (18). The section (18) is reinforced by a tubular metal insert (19).

In fitting or replacing the branch tee, the old branch tee is unscrewed and removed through the bell as previously described, or a new screw-threaded hole is drilled in the distribution main, as appropriate. The adaptor (1) is then inserted into the bell and screwed into position until the 0ring (9) is pressed firmly against the wall of the distribution main. The bell is then removed, and the adaptor remains gas tight as the annular bore (3) is sealed by the knock-out plug (10). After pressure testing the subscriber's system, the reinforced end (18) of the service pipe (16) is inserted into the annular bore (3) and pushed down until it contacts the knock-out plug (10). The plug (10) is displaced by the downward passage of the end of the service pipe and falls into the distribution main, allowing gas to flow to the subscriber.

In certain circumstances, the use of the bell can be dispensed with, and the hole in the distribution main simply plugged by hand using a rag whilst the changeover of the adaptor for the branch tee is carried out.

In an alternative embodiment, the reinforcing metal insert (19) can be extended, as shown at 20, and provided with serrated teeth or castellations (21) to provide a gas path behind the knock-out plug or to pierce or sever the knock-out plug (10).

In a further alternative embodiment, as shown in Figure 3, the reinforced section (18) of the service pipe (16) can be provided with annular lugs (22), which act to seal the internal bore of the adaptor, or with annular indentations (23), which cooperate with the gas seals and end-loading rings (15) to seat the pipe firmly within the annular bore (3).

Referring now to Figures 4 and 5 of the Drawings, the adaptor, designated generally at 30, comprises a body portion (31) having an annular internal bore (32). The body has an upper external polygonal section (33), and a lower external threaded section (34) which is adapted to cooperate with the internal threaded bore of the hole in a distribution main. An external annular sealing means (35), situated between the upper polygonal section (33) and the lower threaded section (34) comprises an annular flange (36) having an annular recess (37) within which is situated an 0being (38) of generally rectangular cross-section, and made of resilient polymeric material.

The internal bore (32) of the adaptor is provided with a knock-out plug (39) which is clipped in the bore (32). A second O-ring (40) is position in an annular recess in the internal bore (32) adjacent a shoulder (41).

The service pipe (42), formed from a suitable grade of high density polyethylene, has an elbow (43) and a reinforced end section (44). The end section is reinforced by a tubular metal insert (45) and is provided with a shoulder (46) which cooperates with the shoulder (41) in the annular bore and the O-ring (40) to form a gas-tight seal.

A security clip (47) has generally C-shaped jaws (48) which are positioned around the service pipe (42) such that the clip is seated between an annular shoulder (49) on the service pipe and the rim (50) of the adaptor body (31).

The service pipe (42) is arranged to be rotatable in the adaptor body (31) so that the outlet of the elbow may be freely rotated to any desired position. This enables the adaptor to be screwed to the main to effect a seal without the necessity to rotate the whole arrangement on the screw thread to bring the outlet of the service pipe to the correct position.

In fitting or replacing the branch-tee, the old branch tee is removed, or a new screw-threaded hole drilling in the distribution main, as previously described. The adaptor is then screwed to the main and the service pipe connected to the subscriber service. The entire subscriber service line is then pressure tested against the knock-out plug. The knock-out plug (39) is resiliently clipped or otherwise retained in the bore (32) by retaining means that are sufficient to retain the plug against a pressure test of the service pipe (42) but such that the plug can be displaced by the application of reasonable force on the top of the elbow (43).

To introduce live gas from the distribution main into the subscriber service line the security clip is first removed and the service pipe pushed down to dislodge the knock-out plug into the service main, allowing gas to enter the subscriber line. To provide a good seating for the annular seal provided by the O-ring (40), the service pipe is then pulled back until the shoulders (41) and (46) are in close proximity, and the clip is then replaced to maintain the service pipe in position.

Although the invention has been described with reference to the connection of a service pipe to a gas distribution main, it is not limited thereto, and it will be apparent that the invention can be applied to other pipe connections and in particular to the connection of pipes carrying water, sewage or other liquids.

The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps or any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

Claims

1 A method of fitting or replacing a branch tee in a gas distribution main which comprises: inserting an adaptor into a hole in a wall of the distribution main, the adaptor having a rigid body with an internal bore therein, the internal bore being provided with a displaceable blocking means, and inserting a service pipe into the internal bore of the adaptor so as to displace the blocking means and open the internal bore of the adaptor, there being provided sealing means between the distribution main and the adaptor and between the adaptor and the service pipe such that the service pipe is connected to the distribution main in a gas tight manner.

2 A method according to claim 1, in which the adaptor has a screw-threaded external section which cooperates with a screw-threaded hole in the distribution main.

3 A method according to claims 1 and 2 in which the adaptor is provided with an external annular seal which, in operation, seals the adaptor against the external wall of the distribution main.

4 A method according to claim 3, in which the external annular seal comprises an 0being seated in a recess in an annular flange.

5 A method according to any of the preceding claims, in which the internal bore of the adaptor is provided with an internal annular seal to seal the bore against the external wall of the service pipe.

6 A method according to claim 5, in which the internal annular seal comprises annular gas seals and end-loading rings.

7 A method according to any of the preceding claims in which the displaceable blocking means comprises a knock out plug.

8 A method according to claim 7, in which the knock out plug is seated in a recess at the distribution main end of the internal bore of the adaptor.

9 A method according to any of the preceding claims, in which the service pipe is an elbow pipe.

10 A method according to any of the preceding claims, in which the wall of the service pipe which is inserted into the adaptor is reinforced with an internal metal insert.

11 A method according to any of the preceding claims, in which the service pipe is provided with external lugs or indentations which themselves form a seal or cooperate with an internal annular seal on the adaptor to improve the gas-tightness of the joint between the adaptor and the service pipe.

12 A method according to any of the preceding claims, in which the service pipe and/or the metal insert is provided with serrated or castellated legs or teeth.

13 A method according to any of the preceding claims, in which there is provided a security means which, when in place, prevents the service pipe from being pushed or driven sufficiently far into the annular bore to displace the blocking means.

14 A method according to Claim 13, in which the security means comprises a C-shaped collar which engages with an annular flange, ledge, recess, rim, collar or shoulder on the service pipe and rests on a rim or other portion of the body of the adaptor, thereby preventing the service pipe from being pushed or driven further into the adaptor.

15 A method according to Claim 13 or 14, in which the security means is removed to allow the service pipe to be pushed or driven into the adaptor to displace the blocking means, and the pipe is then pulled back to allow the security means to be replaced.

16 A method according to any of the preceding claims, substantially as hereinbefore described.

17 An adaptor for use in a method according to any of claims 1 to 16, which comprises a rigid body having an internal bore therein, the internal bore being provided with a displaceable blocking means and an internal annular seal, the body having a screw-threaded external section and an external annular seal.

18 An adaptor according to claim 17 substantially as hereinbefore described with reference to and as illustrated in Figure 1 of the accompanying Drawings.

19 A pre-assembled adaptor assembly for use in a method according to any of Claims 1 to 16, which comprises an adaptor according to Claim 17 or 18 together with a service pipe inserted therein.

20 An adaptor assembly according to Claim 19, in which the service pipe is rotatable in the adaptor body.

21 An adaptor assembly according to Claim 19 or 20 substantially as hereinbefore described with reference to and as illustrated in Figures 4 and 5 of the accompanying Drawings.