GB2227290A - Connecting a branch to a pipe - Google Patents

Abstract

A method for connecting a branch pipe 23 or connector to a pipe 1 comprises forming a first aperture in the outer casing of the pipe 1 without damaging a lining 2 so as to provide a reservoir 16, filling the reservoir 16 so formed with a liquid resin, forcing the lining 2 inwardly with a screw wedge 18-20 to provide between the lining 2 and the pipe 1 a clearance (21, Fig 4) into which the liquid resin 22 is drawn, releasing the force to allow the lining 2 to return to its original position, allowing the resin 22 to cure, forming a second aperture in the pipe 1 contiguous with the first aperture, forming an opening in the lining 2 in line with the second aperture and securing the end portion of the branch pipe 23 or of the pipe connector to the wall surrounding the second aperture. The pipe 1 may be live. The cured resin 22 prevents tracking arising from an incomplete bond between the lining 2 and the pipe 1. <IMAGE>

Description

TITLE: METHOD FOR JOINING PIPES The present invention relates a method for joining pipes and particularly for joining to the wall of a first pipe of the type having an outer casing and a lining, an end portion of a second pipe or of a pipe connector for a second pipe.

Such first pipes as those mentioned may comprise fluidcarrying mains in which the outer casing is of a metal such as cast iron and the inner lining is a hose of textile or like material bonded to the inner wall of the casing or is itself a close-fitting pipe of a plastics material such as polyethylene, the fluid being gas, water or sewage.

The second pipes may be service or branch pipes for connecting the main to a dwelling.

In making the connection between the main and the service or branch pipe or the pipe connector it is necessary to form an aperture in the wall of the casing and the lining and then to connect the pipe or connector to the wall of the aperture so formed.

Unfortunately with connections made in the conventional manner described there has been observed so called "tracking" of the fluid. This is the phenomenon of fluid escape between the outer wall of the service or branch pipe or connector and the wall of the aperture into the boundary area between the outer casing and the lining due to an incomplete bond between the hose lining and the casing or because the fit between the plastics liner and the casing is not sufficiently close.

Such fluid may subsequently travel along this boundary only to emerge from the pipes as an apparent localised leak at some point or points distant from the connection for example, at a joint between portions of the casing.

It may be necessary to effect several subsequent leak repairs to prevent fluid escaping at these points although fluid is in fact only leaking at one point. However, it is in practice very difficult to detect the actual source of a leak of this type.

It is therefore an object of the present invention to provide a method of joining pipes in which the risk of fluid tracking occuring is reduced.

According to the present invention, we provide a method for joining to the wall of a first pipe of the type having an outer casing and a lining an end portion of a second pipe or of a pipe connector for a second pipe, the method comprising forming a first aperture in the outer casing of the first pipe without damaging or puncturing the lining so as to provide a reservoir between the wall surrounding the first aperture and the now exposed lining to contain a curable liquid resin, filling the reservoir so formed with the liquid resin, forcing the lining inwardly while the resin is still liquid to provide between the lining and its casing a clearance into which the resin can be drawn, allowing the resin to be drawn into the clearance, releasing the force to allow the lining to return to its original position, allowing the resin to cure, forming a second aperture in the outer casing contiguous with the first aperture, forming an opening in the lining contiguous with the second aperture and securing the end portion of the second pipe or of the pipe connector to the wall surrounding the second aperture.

An embodiment of the invention will now be particularly described with reference to the drawings in which : Figure 1 shows a longitudinal section through a typical fluid carrying lined pipe to which has been fitted as an initial step a standard drilling assembly, also shown in section, Figure 2 shows a second step in the method, Figure 3 shows a third step in the method, Figure 4 shows a fourth step in the method, Figure 5 shows a fifth step in the method, Figure 6 shows a sixth step in the method, Figure 7 shows a seventh step in the method, and Figure 8 shows the completion of the method with the service pipe connected to the lined pipe.

Referring to the drawings, the lined pipe comprises a gas main having an outer casing 1 of cast iron and an inner lining 2 bonded to the inner wall 3 of the casing 1, the lining 2 comprising a hose of textile material.

As a first step (Figure 1), a known type plate valve 4 e.g. that manufactured by Wask Ltd., is releasably attached to the outer wall of the casing 1 at the point where it is intended to attach the service pipe to the main. The plate valve 4 may be attached by any well known means for example a circumferential chain (not shown) whose ends are releasably attached to the valve 4 after the chain has been passed around the casing 1.

Next, a known type e.g. Wask Ltd., sealing bonnet 5 is releasably but sealably secured to the valve 4 in the known manner.

Finally, a known type hole saw 6, e.g. that manufactured by Starrett Ltd., is inserted into the central bore 7 of the bonnet 5 with its front end 8 seated in the uppermost recess 9 formed in the valve 4 above the closed slidable plate 10, the cylindrical body 11 of the saw 6 forming a seal with the uppermost end 12 of the bore 7 of the bonnet 5.

The hole saw 6 has a cylindrical shank 13 consisting of a set of circularly arranged teeth 14 at its front end in front of a tapping drill 15 (Figure 2).

In the next step (Figure 2), the slidable plate 10 is slid to the open position, and the shank 13 of the saw 6 is extended downwardly until the teeth 14 of the saw 6 engage with the cast iron casing I and the shank 13 is rotated so that the teeth 14 cut out a circular coupon from the casing 1, without damaging or puncturing the lining 2.

When the saw 6 has cut through the casing 1 there is a distinct change in the pressure needed for the cutting operation signalling that the coupon has been cut out.

The hole saw 6 is then withdrawn through the bonnet 5 and the metal coupon and any swarf present is removed from the toothed front end of the saw 6. The bonnet 5 is then temporarily removed from the plate valve 4.

A rapid setting two part liquid epoxy adhesive eg.

Lockshield Rapid Epoxy manufactured by Chemence Ltd., is then prepared. This mixture is poured into the reservoir 16 now formed (by the removal of the metal coupon) between the lining 2 and the wall 17 of the aperture in the casing 1 (Figure 3).

In the next step of the method (Figure 3) the bonnet 5 is reattached to the valve 4 and a standard screw wedge 18 is secured to the bonnet 5 as shown.

The threaded shank 19 of the screw wedge 18 is then screwed downwardly through the valve 4 and into the reservoir 16 until the spherical front end 20 of the wedge 18 engages with the lining 2.

The shank 19 is then screwed downwardly a further distance to cause the lining 2 to be depressed inwardly away from the inner wall 3 of the casing 1 to create clearance 21 between the lining 2 and the inner wall 3 of the casing 1 (Figure 4). This action causes the liquid adhesive 22 to be drawn into the clearance 21 so formed.

The screw wedge 18 is then removed from the bonnet 5 and this allows the lining 2 to relax and return to its original position thereby squeezing excess adhesive back into the reservoir 16. The plate 10 is then slid closed (Figure 5) and the adhesive is allowed to cure.

In the next step of the method (Figure 6) the plate 10 is slid open and the hole saw 6 is re-inserted into the central bore 7 of the bonnet 5. The shank 13 of the saw 6 is driven downwardly until the teeth 14 of the saw 6 engage with the now cured adhesive 22 and cut out a circular coupon of adhesive and a contiguous circular portion of the lining 2. The shank 13 is then extended downwardly still further so that the threaded portion of the tapping drill 15 engages and tap the wall of the aperture previously formed in the casing 1.

The shank 13 is then withdrawn until its teeth 14 are above the opening in the plate valve 4 and the plate 10 is closed to prevent gas from escaping into the atmosphere through the opening now formed in the wall of the gas main. The hole saw 6 is then removed from the bonnet 5.

The service pipe 23 to be connected to the main is provided with a removable internal sealing valve 24 (diagrammatically shown in Figure 7) to seal off the pipe bore 25 temporarily while it is being connected to the main. The threaded end 26 of the pipe 23 is then coated with a newly prepared quantity of the adhesive and the pipe 23 is inserted into the bore of the bonnet 5 (Figure 7) and then into the mouth 27 of the plate valve 4 with which the outer wall of the pipe 23 forms a slidable seal.

The plate 10 of the plate valve 4 is slid open and finally the pipe 23 is screw connected to the now threaded wall of the aperture in the wall of the gas main.

Finally the bonnet 5 is removed from the plate valve 4 over the pipe 23 and the plate valve 4 is then itself removed from the casing 1 of the main over the service pipe 23 so that the position shown in Figure 8 is reached.

The sealing valve 24 may subsequently be removed to connect the pipe 23 to the inlet of a gas meter inside the dwelling.

The adhesive serves to provide a strong fluid tight bond between the threaded end of the service pipe 23 and the threaded internal wall of the aperture in the casing 1.

Similarly the adhesive causes the lining 1 to form a strong fluid tight bond with the inner wall 3 of the casing 1 in the immediate area circumventing the aperture in the casing 1.

Tests have revealed that the incidence of tracking previously described is virtually eliminated if this technique is used to attach a service pipe or pipe connector to the wall of a lined gas main.

While the description is concerned with the attachment of a service pipe or pipe connector to a so-called "live" gas main, ie. a main through which gas is flowing, it has equal utility to the case where the main is "dead" ie. the gas flow has been shut-off temporarily. In this latter case of course the plate valve and bonnet can be dispensed with.

Claims (8)

1. A method for joining to the wall of a first pipe of the type having an outer casing and a lining an end portion of a second pipe or of a pipe connector for a second pipe, the method comprising forming a first aperture in the outer casing of the first pipe without damaging or puncturing the lining so as to provide a reservoir between the wall surrounding the first aperture and the now exposed lining to contain a curable liquid resin, filling the reservoir so formed with the liquid resin, forcing the lining inwardly while the resin is still liquid to provide between the lining and its casing a clearance into which the resin can be drawn, allowing the resin to be drawn into the clearance, releasing the force to allow the lining to return to its original position, allowing the resin to cure, forming a second aperture in the outer casing contiguous with the first aperture, forming an opening in the lining in line with the second aperture and securing the end portion of the second pipe or of the pipe connector to the wall surrounding the second aperture.

2. A-method as claimed in claim 1 in which the apertures and the opening are drilled out.

3. A method as claimed in claim 1 or claim 2 in which the end portion of the second pipe or of the pipe connector is threaded and the wall of the second aperture is tapped after drilling whereby the end portion can be screw connected to the wall of the second aperture.

4. A method as claimed in claim 3 in which before the end portion of the second pipe or of the pipe connector is screw connected to the wall of the second aperture it is coated with the curable liquid resin.

5. A method as claimed in any of the preceding claims in which the resin is an epoxy adhesive.

6. A method as claimed in any of the preceding claims in which the lining comprises a hose type lining or a close fitting plastics liner pipe.

7. A method as claimed in any of the preceding claims in which the first pipe is a fluid transporting pipe and the opening in the lining is formed and the end portion of the second pipe or of the pipe connector is connected to the second aperture without the escape of fluid to the atmosphere.

8. A method substantially as hereinbefore described with reference to the accompanying drawings.