GB2299647A

GB2299647A - Replacement pipe laying system

Info

Publication number: GB2299647A
Application number: GB9607301A
Authority: GB
Inventors: Anthony William Spooner
Original assignee: A W Spooner & Co Ltd
Current assignee: A W Spooner & Co Ltd
Priority date: 1995-04-07
Filing date: 1996-04-09
Publication date: 1996-10-09
Also published as: GB9607301D0

Abstract

A damaged buried plastic pipe 12, e.g. between an external stopcock and house stopcock is replaced by passing a line 30 through the pipe, attaching a replacement pipe to one end of the line, and pulling on the other end of the line to draw the existing pipe out of its course and the replacement pipe into that course. The line 30 is pulled by a manual winch 25 attached to one of three bulkheads 21-23 on a frame 24. Plate 21 abuts against the ground, and has an entry cone 50 for guiding the incoming pipe. Plate 22 carries releasable blades for splitting the incoming old pipe, and rollers 56 and 57 guide the split pipe portions away from the line 30.

Description

Pipe L:yirlg System The present invention relates to pipe laying systems, and more specifically to systems for replacing or renewing underground pipes of plastics materials.

The supply of mains water to domestic and other premises is virtually universal, end it is equally almost universal for the mains supplies to be by means of buried pipes. Water pipes have traditionally been of metal. However, the use of plastics materials (plastic pipes) for such pipes is becoming popular, both internally and externally, and many premises now have plastic mains supply pipes.

Such pipes are usuelly made of polyethylene.

Although buried pipes may at first sight appear to be well protected, they are in fact often subjected to considerable stresses. Although the material of the pipes themselves may be resilient, the surrounding earth may subject it to considerable force. For example, the earth may contain sharp gravel or stones which can abrade the pipe as a result of vibration. heave, settlement, erosion due to water flow through the earth, and other causes. Accidental damage es a result of digging can also occur. Plastic pipes may therefore become damaged to the extent that leakage occurs, with replacement therefore becoming necessary.

The standard technique for replacement involves gaining access to substantially the entire length of the pipe, which will typically run for several metres from a main external stopcock to a stopcock located immediately inside the house or other building. This involves digging a trench along the path of the pipe (which will cause considerable damage to gardens. drives, etc) and often also making a substantial internal access hole through concrete flooring. (Of course, it is not strictly necessary to gain access to and remove the demaged pipe; but a route for the new pipe has to be prepared for the new pipe between the external and internal stopcocks. and using an alternative route will usuelly cause even more disturbance and damage.) A "mole" can sometimes be used to drill a path for e pipe along a roughly horizontal route, and its route can to some extent be controlled. However, this still requires large excavations at the two ends of the pipe route, and there are the twin dangers of the mole either meeting and damaging some other service along its route or meeting some impenetrable obstacle. Also, moles are expensive to operate.

The general object of the invention is to provide an improved pipe installation system for replacing external buried plastic pipes.

According to one aspect, the invention provides a method of replacing a buried plastic pipe by passing a line through the pipe, attaching a replacement pipe to one end of the line, and pulling on the other end of the line to draw the existing pipe out of its course and the replacement pipe into that course.

Preferably the existing pipe is split as it emerges from the ground to separate it from the line.

According to another aspect, the invention provides Apparatus for replacing a buried plastic pipe comprising: e line to be passed through the existing pipe and having termination means for holding a replacement pipe; winch means for pulling the other end of the line; end means for splitting the existing pipe adjacent to the winch means.

Further features of the invention will become apparent from the following detailed description of an embodiment thereof, given by way of example, and with reference to the drawings, in which: Fig. 1 is a general view of a house with a plastic water supply pipe; Fig. 2 is a perspective view of a puller unit; Fig. 3 is a larger scale view of a replacement pipe drilling means; Fig. 4 is a larger scale view of the termination of a puller wire; and Fig. 5 is a larger scale view of the cutter plate of the puller unit.

All the drawings are in simplified and diagrammatic form, with parts cut away or omitted as convenient.

Fig. 1 shows a typical situation in which the present system may be used.

A house 10 is connected to a mains water supply II by means of a plastic pipe 12 buried in the ground 13. The pipe 12 is connected at one end to the mains supply 11 by an external stopcock 14, and at the other end to the rising main of the house plumbing (not shown) by an internal stopcock 15. As shown, the pipe 12 rises from the ground directly into the house, typically through a concrete floor 16.

As discussed above, the pipe 12 may become damaged in the ground 13.

Such damage eventually results in a leak, which is typically discovered as a result of the ground becoming wet. When this happens, it is necessary to replace the existing pipe 12 by a new replacement pipe.

The conventional way of replacing the pipe 12 is to dig a trench along its course through the ground outside the house, from the stopcock 14 onwards, and to break through the floor 16 in the house to complete the opening of the course of the pipe. The existing pipe can then readily be removed and the replacement pipe fitted. The trench is then filled in and its surface made good as well as may be, and the floor 16 similarly repaired and made good. This procedure is expensive and normally results in lasting damage to any drives, footpaths, etc through which the trench passes, and to the flooring of the house where the pipe enters.

In the present system, the existing pipe 12 is replaced by a replacement pipe following the same course as the existing pipe. As in the conventional system, the stopcock 14 is first closed, the water system of the house drained down, and the existing pipe disconnected from the internal and external stopcocks 14 and 15; then when the replacement pipe has been put in place, it is connected to the two stopcocks, the external stopcock 14 turned on, and the system checked for leaks.

In the present system, an excavation 17 is made at the external stopcock 14, typically some 1.5 m long, 0.5 m wide, and 0.2 m below the line of the existing pipe. Also, the floor 16 has to be broken through to expose the existing pipe until an underfloor cavity or loose earth is reached. However, no trench is required between the excavation 17 and the house, and the hole in the floor 16 need only be large enough to allow free passage of the pipes; no access through the floor is required beyond that. The present system thus causes much less damage than the conventional system; it is also cheaper and quicker.

The main component of the apparatus of the present system is a puller unit 20, which is placed in the excavation 17. As shown in Fig. 2, the puller unit comprises a framework formed by 3 bulkheads or plates 21, 22, and 23 connected by 4 bars 24. Plate 21 forms a pressure plate which bears against the house end of the excavation 17 and guides the entry of the pipes; plate 22 forms a stripper plate which cuts the existing pipe; and plate 23 forms a back plate, to which a winch 25 is attached.

Associated with the puller unit is a steel wire 30, which has a termination fitting firmly attached to one end. This wire is used to pull the replacement pipe into position while the existing pipe is simultaneously drawn out of its course. For this, the wire has its termination attached to the replacement pipe and has its other end threaded into and through the existing pipe from the house end toward the excavation 17. In the excavation, the wire is gripped and pulled by the puller unit 20. The leading end of the replacement pipe abuts against the house end of the existing pipe 12, forcing thet pipe along through its course to emerge at the puller unit and being itself pulled into that course to replace the existing pipe.The existing pipe 12 is thus ectuelly pushed out of its course; the wire 30 is of course under tension inside the existing pipe and prevents that pipe from buckling as it is pushed out.

In more detail, a suitable length of replacement pipe 40 is teken. The end of this pipe 40 (Fig. 3) is first prepared using a die 41 and drill 42. The die 41 comprises a handle 43 carrying a stub tube 44 with a pair of guide holes 45 opposite each other in its sides. The end of the pipe 40 fits into the stub tube 44, and a pair of holes 46 are then drilled through the end of the pipe 40 by using the drill 42. A countersink 47 is then cut in the outer part of one of the holes 46 (after the end of the pipe has been taken out of the die 41, of course) with a suitable tool (not shown).

The wire 30 has a termination 31 (Fig. 4) at its end. This termination may be attached rigidly to the wire, but may consist of a unit which cen be slid along the wire to engage with a fitting swaged or otherwise formed rigidly on the end of the wire.

The termination 31 has a portion 32 which fits into the end of the existing pipe 12; this portion 32 mey have its end chamfered to assist in fitting it into the pipe 12. The termination also has a portion 33 which fits into the end of the replacement pipe 40, and has a pair of threaded holes 34 which correspond to the holes 46 in the end of the replacement pipe 40. A bolt 35 with a countersunk head is passed through the aligned holes 34 and 46, so attaching the end of the replacement pipe 40 firmly to the termination 31 of the wire 30, with its end abutting against the end of the existing pipe 12. The ends of the bolt 35 should both be substantially flush with the surface of the pipe 40.

If desired, the termination 31 can be provided with a central circumferential flange against which the ends of the two pipes will abut, and further holes can be provided in the portion 33 to enable the replacement pipe to be attached to it more firmly. The length of the termination 31 should not be too greet, however, as it (and the attached portions of pipe) mey have to negotiate e curved course.

At the excavation 17, the existing pipe 12 is cut awey to leeve a short length projecting from the eerth. The end plate 21 of the puller unit 20 has a tapered guide tube or cone 50 attached to it, and the puller unit is placed in the excavation with plate 21 towards the cut end of the pipe 12 and moved to that end so that the end of pipe 12 enters and pesses through the guide cone 50.

When the wire 30 is fed into the house end of the pipe 12, its end emerges in due course from the end of the pipe 12. This emerging end of the wire is passed through an aperture 51 in plate 22, end on into the winch unit 25, emerging from the side of that unit towards its rear.

The winch unit is a hand-operated unit attached firmly to the other end plate 23 of the puller unit. It can be locked onto the wire 30 to grip it firmly, and then operated, by means of an operating lever. to pull the wire through the plates 21 and 22; if desired, the wire can be moved back to slacken it by means of a second operating lever. Operating the winch therefore pulls the wire through the puller unit; as a result, the termination 31 at the other end of the wire pushes the existing pipe 12 along its course towards the puller unit and pulls the replacement pipe 40 along through the course being vacated by the existing pipe 12.

It may be desirable to manually guide and push the replacement pipe at the house end of its course, to prevent it from being damaged as it passes through the opening in the concrete floor. A lubricant cen be applied to the pipe at this location, or even pumped into the replacement pipe to emerge at the wire termination, to ease the passage of the pipe through the ground.

As the pipe 12 moves along its course, its end will soon reach the aperture 51 in plate 22. Plate 22 carries a pair of flanges 53 (Fig. 5) to which a pair of cutter blades 52 are bolted; the bolt holes in the flanges 53 through which the bolts (not shown) pass are elongated, as shown at 54, to allow the positions of the cutter blades to be adjusted. The blades are set so that they cut through the wall of the pipe 12, so cutting this pipe into two separate portions 12A and 12B. The pipe is thus separated from the wire 30 as it emerges from the ground, so that the entire length of the wire can be pulled through the course of the pipe 12 by the winch 25.

The puller unit 20 Includes a frame 55 carrying a horizontal guide or roller 56 and vertical guides and rollers 57 arranged above the centre line of the puller unit. The ends of the pipe halves 12A end 12B can be inserted into the upper corners of the frame as the pipe 12 starts to be cut; the cut halves of the pipe will then automatically emerge from the excavation 17 as the pipe 12 continues to be moved along its course.

When the junction between the existing pipe 12 and the replacement pipe 40 comes out of the guide 50 and into view, pulling of the wire 30 is stopped. In practice, the plastic piping used in the past has generally been black, while the plastic piping used currently is generally blue polyethylene. The junction between the two pipes is therefore readily visible. If necessary, however, other techniques can be used to identify the junction, eg by placing a coloured adhesive tape around the junction, trapping a thin sheet of coloured plastic material between the end of one of the pipes and the wire termination, or using a wire termination with a flange visible between the ends of the pipes.

The cutter blades 52 on the plate 22 are released and moved outwards, so that the junction can be pulled through the plate 22 for easy access. The tension of the wire is then released, and the bolt 35 is unscrewed from the wire termination 31, releasing the end of the replacement pipe 40. The wire is then withdrawn manually from the winch and the remaining uncut stub of the existing pipe 12. The puller unit is then removed from the excavation, and the replacement pipe is pulled manually to bring its end to the external stopcock for connection. Finally, the replacement pipe is connected to the two stopcocks 14 end 15, the system tested, and the excavation 17 and the hole in the floor 16 filled and made good.

Obviously the cutter blades 52 could be mounted on racks or hinges, if desired, to allow them to be more easily adjusted and released.

If desired, means can be provided to engage with and pull on the emerging end of the existing pipe 12 (or the cut portions 12A and 12B), to assist in drawing it from its course in the earth.

Claims

1 A method of replacing a buried plastic pipe by passing a line through the pipe, attaching a replacement pipe to one end of the line, and pulling on the other end of the line to draw the existing pipe out of its course and the replacement pipe into that course.

2 A method according to claim 1 wherein the existing pipe is split as it emerges from the ground to separate it from the line.

3 Apparatus for replacing a buried plastic pipe comprising: a line to be passed through the existing pipe and having termination means for holding a replacement pipe; winch means for pulling the other end of the line; and means for splitting the existing pipe adjacent to the winch means.

4 Apparatus according to claim 3 wherein the splitter means comprise releasable blades.

5 Apparatus according to either of claims 3 and 4 comprising a frame having a first bulkhead for engagement with the ground, a second bulkhead carrying the splitting means, and a third bulkhead to which the winch means is attached.

6 Apparatus according to claim 5 including also roller means for guiding the split portions of the existing pipe.

7 Apparatus according to either of claims 5 and 6 including an entry cone attached to the first bulkhead for receiving the pipe.

8 Apparatus according to any of claims 3 to 7 including drilling means for drilling the end of the replacement pipe for attachment to the line termination means.

9 A method of replacing a buried plastic pipe substantially as herein described and illustrated.

10 Apparatus for replacing a buried plastic pipe substantially as herein described and illustrated.