GB2051991A - Method of and apparatus for making a connection to a pipe - Google Patents

Abstract

A service connection to a pipe, particularly a gas main, employs a flexible connecting member (3) which is distorted by means of a rigid mandrel (6) so that its outer-surface (7) forms a seal with the edge (8) of a hole (2) in the wall (1) of the pipe. <IMAGE>

Description

SPECIFICATION Method of and apparatus for making a connection to a pipe This invention relates to methods of making connections to service pipes, particularly gas supply pipes, and to apparatus therefor.

Presently connections from steel or cast iron mains to service pipes of polyethylene or like plastics materials are made using a metallic coupling of malleable iron, steel or gun metal provided with a male thread inlet connection. A hole is drilled through the wall of the service pipe and a female thread tapped therein. A back nut, saddle and rubber seal which is compressed on to the main wall are used to make a gas-tight joint.

The outlet connection is made through a mechanical coupling, using either a rubber seal and gland nut or compression ring to form the seal. An internal plug is used to close the inlet connection during insertion of the tee and pressure testing of the service.

The connecting tee is inserted using a machine which both drills and taps the main pipe and then permits the tee to be screwed into the pipe. The machine base is attached to the pipe through an intermediate seal and is held in position by means of a chain clamp. It incorporates a sliding gate valve which permits the attachment of interchangeable top members at different stages during the sequence of operations.

After clamping the base to the pipe by means of the chain clamp, a drilling and tapping machine is fitted to a drilling head which is then attached to the base. The gate valve is then opened and a hole drilled through the wall of the service pipe. The hole is tapped with a female thread the drill is raised and the gate valve is closed. The drilling head is then removed. A service tee with a male connecting thread is fitted into a tee head which is then attached to the base. The gate valve is again opened and the service tee lowered and screwed into the threaded hole in the pipe. The head and base are removed from the pipe, the service tee is suitably aligned and a back nut is tightened to form a seal on to the pipe. The connection to the service pipe is then completed and, after a pressure test has been carried out, an internal plug is raised and the connection is completed.

This method suffers from a number of disadvantages. Steel and malleable iron tees in current use are thin and subject to corrosion.

Factory applied corrosion protection may be damaged during tightening; corrosion protection thus depends on measures taken on site and is frequently inadequate. Gun metal tees are more expensive and still need wrapping to avoid galvanic corrosion of an adjacent main. A rubber seal is required to make gas-tight joint and this is often a source of leakage. Assembly is slow due the number of different steps to be carried out.

Finally, the method can be dangerous since it is possible to bypass some of the stages and screw the tee into an open hole whilst gas is blowing from the pipe.

In order to overcome these problems a novel method of connection has been devised based on a flexible connecting member and a rigid mandrel connecting member and a rigid mandrel.

According to one aspect of the invention there is provided a method of making a connection to a pipe comprising drilling or otherwise forming a hole in the wall of said pipe, inserting a flexible connecting member and rigid mandrel means into said hole and urging said connecting member and said mandrel means towards one another to distort said connecting member and thereby form a seal between said connecting member and the edge of said hole.

According to a second aspect of the invention there is provided apparatus for making a connection to a pipe comprising flexible connecting means having a surface adapted to form a seal with the edge of a hole through the wall or said pipe and rigid mandrel means adapted to cooperate with said connecting means so that in a first relative position said connecting meals and said mandrel means can be inserted into said hole and in a second relative position said mandrel means distorts said flexible connecting means so that said surface forms a seal with the edge of the hole through the pipe wall.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows in section a connection to plastics pipe in accordance with an embodiment of the invention Figure 2 shows an alternative connection employing a nipple Figure 3 shows an insertion and clamping tool for making the connection illustrated in Figure 1 Figure 4 shows a front view of part of the insertion and clamping tool of Figure 3, and Figure 5 illustrates the use of the insertion and clamping tool for making a connection with a nipple.

Referring now to the drawings, a polyethylene gas supply main 1 has a hole 2 drilled therethrough. A non-tapped flexible connecting tee 3 of polyeth,tlene having an integral socket outlet 4 into which a service pipe 5 can be fused directly, and a rigid, tapered steel mandrel 6 are inserted into the hole 2. The outer surface 7 of the connecting tee forms a loose fit with the complementary edge 8 of the supply main. The connection is made by forcing the mandrel and connection tee together thereby distorting the connection tee by means of the tapered surface 9 of the mandrel and making a gas-tight seal between the outer surface 7 of the tee and the complementary edge 8 of the supply main.Spring clips 10 together with "fir tree" rings 1 1 on the tapered surface of the mandrel retain the latter in position and maintain the seal to the supply pipe.

The mandrel is provided with holes 12 communicating with the interior 13 of the tee and an internally threaded bore 14 into which is screwed an internal plug 15. This plug has a conical edge 16 which, in the lowered position, makes a gas-tight seal with a complementary surface 17 at the base of the mandrel internal thread to shut off the gas flow. An annular plug 18 having an external thread 19 is screwed into the tee and retains the internal plug and supports the top of the mandrel within the body. A cap 20 and seal 21 complete the gas-tight closure. In some cases the spring clip and "fir-tree" rings may be dispensed with and friction alone used to retain the mandrel. The tee may, optionally, be provided with a support ring 22.

With an alternative form of construction illustrated in Figure 2, a flexible polyethylene nipple 22 is inserted into the hole 2 in the wall of the main pipe 1 together with the mandrel 6. The polyethylene tee body 3 is subsequently fused to the nipple. The closure cap 20 is screwed directly to an internal thread 23 in the tee body and retains the internal plug 1 5 by a captive plate 24.

Referring now to Figures 3 and 4 of the drawings, these illustrate the principles of the method of making a connection to a main pipe 1 using a suitably designed tool. The tool comprises a known multiple component base 41 having interchangeable packing members 42 to accommodate different diameters of pipe and make a seal when they are clamped thereto by means of a chain clamp (not shown). The base is provided with a sliding gate valve 43 which can be opened and closed to provide access to the polyethylene pipe 1. The base accommodates a known demountable top section (not shown) which may be used to hold a drill in juxtaposition to the wall of the pipe 1 and in isolation from the atmosphere. The top section is mounted on the bottom section and is sealed thereto with the gate valve closed. The valve is opened and the drill lowered.A hole is drilled through the wall of the pipe and the drill raised again. The gate valve is then closed and the top section and drill removed.

A further sealable top section 44 is then mounted on the bottom section. This top section includes an enclosure 45 which makes with the bottom section a region 46 sealed from the atmosphere.

Slidably mounted in the enclosure is a tubular member 47 which serves to retain-spring clips 10 within a tee body 3. The tubular member is provided at its top with an internal thread 48 into which is screwed a guide bush 49. Slidably mounted in the bush is an actuating rod 50 to the lower end of which is screwed a mandrel holder bush 51 which has internal 52 and external 53 threads. The mandrel holder bush is screwed into a steel mandrel 6. The upper end of the actuating rod 50 has a thread 54 on which is mounted a retaining nut 55. A spacer washer (not shown) may be provided below the nut. A mandrel raising lever arrangement 56 is inserted between the actuating rod guide bush 49 and the retaining nut 55. The arrangement is located with the aid of hooks 57 on a handle 58. The hooks cooperate with an eye 59 mounted on the top section 44.

The lever arrangement has a fixed handle 60 and a movable handle 61 pivotally mounted thereon by means of an axle 62. Pivoting links 63-65 raise the actuating rod 50 when the handles 60, 61 are brought together.

In operation the top section is sealed to the bottom section, the gate valve is opened and the tee and mandrel inserted into the hole in the wall of the polyethylene pipe. The handles 60,61 are then brought together, raising the actuating rod 50 and mandrel 6, and forcing the outer surface of the tee 3 into a sealed relationship with the wall of the tube. At the same time, the lower surface of the fixed handle 60 forces the guide bush 49 downwards. The bottom end of the tubular member 47 attached to the bush urges spring steel retaining clips 10 downwards to hold the mandrel 6 in position. At this stage, an internal plug 15 is in its lowered position making a seal with the mandrel. The assembly tool is then removed, leaving the sealed connection 3, 6, 1 5, 10 in position.Pressure tests are made in the usual way and the service connection completed by sealing a polyethylene pipe to the tee.

Figure 5 shows a modification of the insertion tool used when a nipple is connected to the polyethylene service pipe instead of a tee. In this case the tubular member 47 which compresses the spring clip 10 bears on the top 63 of the nipple rather than on an internal ledge. The body of the nipple is flexible (as that of the tee) and is likewise distorted by the rigid mandrel 6.

It will be appreciated that variations may be made without departing from the ambit of the invention. For example, it is not necessary for the service connection pipe to be of polyethylene and fused to the connecting tee; a threaded component could also be used. Likewise the combination of a flexible coupling member and a rigid mandrel could be used to make a connection to a pre-drilled metal main pipe.

Claims (22)

1. A method of making a connection to a pipe comprising drilling or otherwise forming a hole in the wall of said pipe, inserting a flexible connecting member and rigid mandrel means into said hole, and urging said connecting member and said mandrel means towards one another to distort said connecting member and thereby form a seal between said connecting member and the edge of said hole.

2. A method as claimed in claim 1 wherein the drilling or other forming of the hole is performed in an enclosure isolated from the ambient atmosphere surrounding the pipe.

3. A method as claimed in either claim 1 or claim 2 wherein the insertion of the connecting member and the mandrel into the hole is performed in an enclosure isolated from the ambient atmosphere surrounding the pipe.

4. A method as claimed in anyone of the preceding claims wherein a service pipe is subsequently coupled to said connecting member.

5. A method as claimed in claim 4 wherein said service pipe is coupled directly to said connecting member.

6. A method as claimed in claim 4 wherein said service pipe is coupled indirectly to said connecting member.

7. A method as claimed in any one of claims 4 to 6 wherein said service pipe is of plastics and is fused to said connecting member.

8. Apparatus for making a connection to a pipe comprising flexible connecting means having a surface adapted to form a seal with the edge of a hole through the-wall of said pipe and rigid mandrel means adapted to cooperate with said connecting means so that in a first relative position said connecting means and said mandrel means can be inserted into said hole and in a second relative position said mandrel means distorts said flexible connecting means so that said surface forms a seal with the edge of the hole through the pipe wall.

9. Apparatus for making a connection to-a-pipe as claimed in claim 8 wherein said mandrel is provided with retaining means to retain it in said second position relative to said connecting means.

10. Apparatus as claimed in claim 9 wherein the retaining means is a spring clip.

11. Apparatus as claimed in either claim 9 or claim 10 wherein the retaining means is a series of projections on the surface of the mandrel means.

12. Apparatus as claimed in claim 11 wherein said series of projections is in the form of fir tree rings.

13. Apparatus as claimed in any one of claims 8 to 12 wherein said mandrel means is provided with plug means to seal the connection to the pipe when in a first position and to free the connection to the pipe when in a second position.

14. Apparatus as claimed in claim 13 wherein retaining means are provided to retain said plug means within said mandrel.

15. Apparatus as claimed in claim 14 wherein the retaining means is a captive plate.

16. Apparatus as claimed in claim 14 wherein the retaining means is an annular plug.

17. Apparatus as claimed in any one of claims 8 to 16 wherein said connecting means is provided with support means to support it and suitably locate it with respect to the wall of the pipe.

18. Apparatus as claimed in any one of claims 8 to 17 wherein attachment means are provided for the attachment of a service pipe to said connecting means.

1 9. A tool for attaching connecting means to a pipe comprising means for making a sealed connection to said pipe, valve means for isolating a region of the surface of said pipe from the ambient atmosphere, means for introducing flexible connecting means together with rigid mandrel means into a hole in the wall of said pipe, and means for urging said connecting means towards said mandrel means.

20. A tool for making a connection to a pipe substantially as herein described with reference to Figures 3. 4 and 5 of the accompanying drawings.

21. Apparatus for making a connection to a pipe substantially as herein described with reference to Figures 1 and 2 of the accompanying drawings.

22. A method of making a connection to a pipe using a tool as claimed in claim 20 or apparatus as claimed in claim 21.